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[pcimem]: Add pcimem Utility
The pcimem application provides a simple method of reading and writing to memory registers on a PCI device. The code used is from https://github.com/billfarrow/pcimem Signed-off-by: Ashwin H [email protected]
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‎rules/pcimem.dep

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SPATH := $($(SONIC_PCIMEM)_SRC_PATH)
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DEP_FILES := $(SONIC_COMMON_FILES_LIST) rules/pcimem.mk rules/pcimem.dep
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DEP_FILES += $(SONIC_COMMON_BASE_FILES_LIST)
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DEP_FILES += $(shell git ls-files $(SPATH))
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$(SONIC_PCIMEM)_CACHE_MODE := GIT_CONTENT_SHA
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$(SONIC_PCIMEM)_DEP_FLAGS := $(SONIC_COMMON_FLAGS_LIST)
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$(SONIC_PCIMEM)_DEP_FILES := $(DEP_FILES)
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‎rules/pcimem.mk

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# pcimem package
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SONIC_PCIMEM_VERSION = 1.0.0
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SONIC_PCIMEM_PKG_NAME = pcimem
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SONIC_PCIMEM = $(SONIC_PCIMEM_PKG_NAME)_$(SONIC_PCIMEM_VERSION)_$(CONFIGURED_ARCH).deb
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$(SONIC_PCIMEM)_SRC_PATH = $(SRC_PATH)/$(SONIC_PCIMEM_PKG_NAME)
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SONIC_DPKG_DEBS += $(SONIC_PCIMEM)

‎src/pcimem/Makefile

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RM := rm -rf
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PCIMEM_TARGET := pcimem
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CP := cp
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MKDIR := mkdir
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CC := gcc
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MV := mv
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-include src/subdir.mk
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ifneq ($(MAKECMDGOALS),clean)
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ifneq ($(strip $(C_DEPS)),)
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-include $(C_DEPS)
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endif
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endif
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all: pcimem-build
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pcimem-build: $(OBJS)
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$(CC) -o "$(PCIMEM_TARGET)" $(OBJS)
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install:
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$(MKDIR) -p $(DESTDIR)/usr/sbin
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$(MV) $(PCIMEM_TARGET) $(DESTDIR)/usr/sbin
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deinstall:
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$(RM) $(DESTDIR)/usr/sbin/$(PCIMEM_TARGET)
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$(RM) -rf $(DESTDIR)/usr/sbin
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clean:
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-$(RM) $(EXECUTABLES)$(OBJS)$(C_DEPS) $(PCIMEM_TARGET)
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.PHONY: all clean dependents

‎src/pcimem/debian/changelog

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pcimem (1.0.0) stable; urgency=medium
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* Initial release.
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-- Ashwin H <[email protected]> Tue, 20 Sep 2022 13:55:00 +0530
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‎src/pcimem/debian/compat

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‎src/pcimem/debian/control

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Source: pcimem
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Section: devel
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Priority: optional
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Maintainer: Ashwin H <[email protected]>
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Build-Depends: debhelper (>= 8.0.0),
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Standards-Version: 3.9.3
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Homepage: https://github.com/sonic-net/sonic-buildimage
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XS-Go-Import-Path: github.com/sonic-net/sonic-buildimage
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Package: pcimem
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Architecture: any
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Built-Using: ${misc:Built-Using}
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description: program to read/write from/to a pci device.

‎src/pcimem/debian/rules

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#!/usr/bin/make -f
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%:
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dh $@

‎src/pcimem/src/LICENSE.txt

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‎src/pcimem/src/README

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== Overview ==
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The pcimem application provides a simple method of reading and writing
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to memory registers on a PCI card.
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Usage: ./pcimem { sys file } { offset } [ type [ data ] ]
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sys file: sysfs file for the pci resource to act on
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offset : offset into pci memory region to act upon
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type : access operation type : [b]yte, [h]alfword, [w]ord, [d]ouble-word
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data : data to be written
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== Platform Support ==
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WARNING !! This method is platform dependent and may not work on your
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particular target architecture. Refer to the PowerPC section below.
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== Example ==
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bash# ./pcimem /sys/devices/pci0001\:00/0001\:00\:07.0/resource0 0 w
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/sys/devices/pci0001:00/0001:00:07.0/resource0 opened.
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Target offset is 0x0, page size is 4096
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mmap(0, 4096, 0x3, 0x1, 3, 0x0)
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PCI Memory mapped to address 0x4801f000.
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Value at offset 0x0 (0x4801f000): 0xC0BE0100
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== Why do this at all ? ==
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When I start working on a new PCI device driver I generally go through a
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discovery phase of reading and writing to certain registers on the PCI card.
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Over the years I have written lots of small kernel modules to probe addresses
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within the PCI memory space, constantly iterating: modify code, recompile, scp
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to target, load module, unload module, dmesg.
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Urk! There has to be a better way - sysfs and mmap() to the rescue.
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== Sysfs ==
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Let's start at with the PCI files under sysfs:
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bash# ls -l /sys/devices/pci0001\:00/0001\:00\:07.0/
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total 0
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-rw-r--r-- 1 root root     4096 Jul  2 20:13 broken_parity_status
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lrwxrwxrwx 1 root root        0 Jul  2 20:13 bus -> ../../../bus/pci
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-r--r--r-- 1 root root     4096 Jul  2 20:13 class
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-rw-r--r-- 1 root root      256 Jul  2 20:13 config
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-r--r--r-- 1 root root     4096 Jul  2 20:13 device
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-r--r--r-- 1 root root     4096 Jul  2 20:13 devspec
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-rw------- 1 root root     4096 Jul  2 20:13 enable
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-r--r--r-- 1 root root     4096 Jul  2 20:13 irq
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-r--r--r-- 1 root root     4096 Jul  2 20:13 local_cpus
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-r--r--r-- 1 root root     4096 Jul  2 20:13 modalias
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-rw-r--r-- 1 root root     4096 Jul  2 20:13 msi_bus
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-r--r--r-- 1 root root     4096 Jul  2 20:13 resource
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-rw------- 1 root root     4096 Jul  2 20:13 resource0
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-rw------- 1 root root    65536 Jul  2 20:13 resource1
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-rw------- 1 root root 16777216 Jul  2 20:13 resource2
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lrwxrwxrwx 1 root root        0 Jul  2 20:13 subsystem -> ../../../bus/pci
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-r--r--r-- 1 root root     4096 Jul  2 20:13 subsystem_device
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-r--r--r-- 1 root root     4096 Jul  2 20:13 subsystem_vendor
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-rw-r--r-- 1 root root     4096 Jul  2 20:13 uevent
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-r--r--r-- 1 root root     4096 Jul  2 20:13 vendor
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The vendor and device files report the PCI vendor ID and device ID:
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bash# cat device
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0x0001
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This info is also available from lspci
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bash# lspci -v
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0001:00:07.0 Class 0680: Unknown device bec0:0001 (rev 01)
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    Flags: bus master, 66MHz, medium devsel, latency 128, IRQ 31
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    Memory at 8d010000 (32-bit, non-prefetchable) [size=4K]
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    Memory at 8d000000 (32-bit, non-prefetchable) [size=64K]
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    Memory at 8c000000 (32-bit, non-prefetchable) [size=16M]
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This PCI card makes 3 seperate regions of memory available to the host
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computer. The sysfs resource0 file corresponds to the first memory region. The
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PCI card lets the host computer know about these memory regions using the BAR
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registers in the PCI config.
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== mmap() ==
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These sysfs resource can be used with mmap() to map the PCI memory into a
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userspace applications memory space.  The application then has a pointer to the
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start of the PCI memory region and can read and write values directly. (There
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is a bit more going on here with respect to memory pointers, but that is all
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taken care of by the kernel).
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fd = open("/sys/devices/pci0001\:00/0001\:00\:07.0/resource0", O_RDWR | O_SYNC);
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ptr = mmap(0, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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printf("PCI BAR0 0x0000 = 0x%4x\n",  *((unsigned short *) ptr);
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== PowerPC ==
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To make this work on a PowerPC architecture you also need to make a small
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change to the pci core. My example is from kernel 2.6.34, and hopefully this
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will be fixed for us in a later kernel version.
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bash# vi arch/powerpc/kernel/pci-common.c
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    /* If memory, add on the PCI bridge address offset */
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     if (mmap_state == pci_mmap_mem) {
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-#if 0 /* See comment in pci_resource_to_user() for why this is disabled */
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+#if 1 /* See comment in pci_resource_to_user() for why this is disabled */
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         *offset += hose->pci_mem_offset;
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 #endif
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         res_bit = IORESOURCE_MEM;
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         /* We pass a fully fixed up address to userland for MMIO instead of
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         * a BAR value because X is lame and expects to be able to use that
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         * to pass to /dev/mem !
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         *
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         * That means that we'll have potentially 64 bits values where some
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         * userland apps only expect 32 (like X itself since it thinks only
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         * Sparc has 64 bits MMIO) but if we don't do that, we break it on
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         * 32 bits CHRPs :-(
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         *
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         * Hopefully, the sysfs insterface is immune to that gunk. Once X
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         * has been fixed (and the fix spread enough), we can re-enable the
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         * 2 lines below and pass down a BAR value to userland. In that case
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         * we'll also have to re-enable the matching code in
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         * __pci_mmap_make_offset().
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         *
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         * BenH.
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         */
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-#if 0
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+#if 1
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        else if (rsrc->flags &amp; IORESOURCE_MEM)
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                offset = hose->pci_mem_offset;
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#endif
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‎src/pcimem/src/pcimem.c

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/*
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* pcimem.c: Simple program to read/write from/to a pci device from userspace.
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*
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* Copyright (C) 2010, Bill Farrow ([email protected])
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*
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* Based on the devmem2.c code
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* Copyright (C) 2000, Jan-Derk Bakker ([email protected])
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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#include <signal.h>
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#include <fcntl.h>
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#include <ctype.h>
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#include <termios.h>
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#include <sys/types.h>
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#include <sys/mman.h>
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#define PRINT_ERROR \
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do { \
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fprintf(stderr, "Error at line %d, file %s (%d) [%s]\n", \
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__LINE__, __FILE__, errno, strerror(errno)); exit(1); \
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} while(0)
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int main(int argc, char **argv) {
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int fd;
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void *map_base, *virt_addr;
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uint64_t read_result, writeval, prev_read_result = 0;
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char *filename;
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off_t target, target_base;
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int access_type = 'w';
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int items_count = 1;
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int verbose = 0;
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int read_result_dupped = 0;
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int type_width;
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int i;
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int map_size = 4096UL;
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if(argc < 3) {
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// pcimem /sys/bus/pci/devices/0001\:00\:07.0/resource0 0x100 w 0x00
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// argv[0] [1] [2] [3] [4]
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fprintf(stderr, "\nUsage:\t%s { sysfile } { offset } [ type*count [ data ] ]\n"
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"\tsys file: sysfs file for the pci resource to act on\n"
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"\toffset : offset into pci memory region to act upon\n"
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"\ttype : access operation type : [b]yte, [h]alfword, [w]ord, [d]ouble-word\n"
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"\t*count : number of items to read: w*100 will dump 100 words\n"
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"\tdata : data to be written\n\n",
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argv[0]);
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exit(1);
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}
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filename = argv[1];
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target = strtoul(argv[2], 0, 0);
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if(argc > 3) {
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access_type = tolower(argv[3][0]);
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if (argv[3][1] == '*')
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items_count = strtoul(argv[3]+2, 0, 0);
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}
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switch(access_type) {
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case 'b':
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type_width = 1;
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break;
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case 'h':
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type_width = 2;
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break;
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case 'w':
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type_width = 4;
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break;
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case 'd':
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type_width = 8;
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break;
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default:
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fprintf(stderr, "Illegal data type '%c'.\n", access_type);
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exit(2);
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}
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if((fd = open(filename, O_RDWR | O_SYNC)) == -1) PRINT_ERROR;
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printf("%s opened.\n", filename);
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printf("Target offset is 0x%x, page size is %ld\n", (int) target, sysconf(_SC_PAGE_SIZE));
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fflush(stdout);
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target_base = target & ~(sysconf(_SC_PAGE_SIZE)-1);
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if (target + items_count*type_width - target_base > map_size)
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map_size = target + items_count*type_width - target_base;
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/* Map one page */
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printf("mmap(%d, %d, 0x%x, 0x%x, %d, 0x%x)\n", 0, map_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, (int) target);
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map_base = mmap(0, map_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, target_base);
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if(map_base == (void *) -1) PRINT_ERROR;
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printf("PCI Memory mapped to address 0x%08lx.\n", (unsigned long) map_base);
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fflush(stdout);
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for (i = 0; i < items_count; i++) {
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virt_addr = map_base + target + i*type_width - target_base;
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switch(access_type) {
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case 'b':
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read_result = *((uint8_t *) virt_addr);
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break;
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case 'h':
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read_result = *((uint16_t *) virt_addr);
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break;
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case 'w':
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read_result = *((uint32_t *) virt_addr);
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break;
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case 'd':
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read_result = *((uint64_t *) virt_addr);
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break;
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}
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if (verbose)
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printf("Value at offset 0x%X (%p): 0x%0*lX\n", (int) target + i*type_width, virt_addr, type_width*2, read_result);
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else {
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if (read_result != prev_read_result || i == 0) {
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printf("0x%04X: 0x%0*lX\n", (int)(target + i*type_width), type_width*2, read_result);
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read_result_dupped = 0;
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} else {
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if (!read_result_dupped)
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printf("...\n");
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read_result_dupped = 1;
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}
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}
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prev_read_result = read_result;
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}
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fflush(stdout);
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if(argc > 4) {
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writeval = strtoull(argv[4], NULL, 0);
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switch(access_type) {
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case 'b':
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*((uint8_t *) virt_addr) = writeval;
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read_result = *((uint8_t *) virt_addr);
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break;
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case 'h':
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*((uint16_t *) virt_addr) = writeval;
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read_result = *((uint16_t *) virt_addr);
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break;
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case 'w':
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*((uint32_t *) virt_addr) = writeval;
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read_result = *((uint32_t *) virt_addr);
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break;
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case 'd':
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*((uint64_t *) virt_addr) = writeval;
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read_result = *((uint64_t *) virt_addr);
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break;
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}
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printf("Written 0x%0*lX; readback 0x%*lX\n", type_width,
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writeval, type_width, read_result);
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fflush(stdout);
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}
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if(munmap(map_base, map_size) == -1) PRINT_ERROR;
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close(fd);
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return 0;
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}

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