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79e3f6ce16
linux/drivers/pci
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Russell King 79e3f6ce16 PCI: mvebu: Use exact config access size; don't read/modify/write 
The idea that you can arbitarily read 32-bits from PCI configuration space,
modify a sub-field (like the command register) and write it back without
consequence is deeply flawed.

Status registers (such as the status register, PCIe device status register,
etc) contain status bits which are read, write-one-to-clear.

What this means is that reading 32-bits from the command register,
modifying the command register, and then writing it back has the effect of
clearing any status bits that were indicating at that time.  Same for the
PCIe device control register clearing bits in the PCIe device status
register.

Since the Armada chips support byte, 16-bit and 32-bit accesses to the
registers (unless otherwise stated) and the PCI configuration data register
does not specify otherwise, it seems logical that the chip can indeed
generate the proper configuration access cycles down to byte level.

Testing with an ASM1062 PCIe to SATA mini-PCIe card on Armada 388.  PCIe
capability at 0x80, DevCtl at 0x88, DevSta at 0x8a.

Before:
  /# setpci -s 1:0.0 0x88.l		- DevSta: CorrErr+
  00012810
  /# setpci -s 1:0.0 0x88.w=0x2810	- Write DevCtl only
  /# setpci -s 1:0.0 0x88.l		- CorrErr cleared - FAIL
  00002810

After:
  /# setpci -s 1:0.0 0x88.l		- DevSta: CorrErr+
  00012810
  /# setpci -s 1:0.0 0x88.w=0x2810	- check DevCtl only write
  /# setpci -s 1:0.0 0x88.l		- CorErr remains set
  00012810
  /# setpci -s 1:0.0 0x88.w=0x281f	- check DevCtl write works
  /# setpci -s 1:0.0 0x88.l		- devctl field updated
  0001281f
  /# setpci -s 1:0.0 0x8a.w=0xffff	- clear DevSta
  /# setpci -s 1:0.0 0x88.l		- CorrErr now cleared
  0000281f
  /# setpci -s 1:0.0 0x88.w=0x2810	- restore DevCtl
  /# setpci -s 1:0.0 0x88.l		- check
  00002810

[bhelgaas: changelog]
Tested-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> (Armada XP GP)
Tested-by: Andrew Lunn <andrew@lunn.ch> (Kirkwood DIR665)
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
2015-10-08 11:22:42 -05:00
..
host PCI: mvebu: Use exact config access size; don't read/modify/write 2015-10-08 11:22:42 -05:00
hotplug PCI: pciehp: Remove ignored MRL sensor interrupt events 2015-08-10 14:24:09 -05:00
pcie PCI: Fix pcie_port_device_resume() comment 2015-07-14 13:41:04 -05:00
access.c PCI: Add dev_flags bit to access VPD through function 0 2015-07-21 13:11:53 -05:00
ats.c PCI: Remove pci_ats_enabled() 2015-08-13 15:59:59 -05:00
bus.c PCI: Add pci_bus_addr_t 2015-05-29 17:21:45 -05:00
host-bridge.c Merge branch 'pci/misc' into next 2015-04-10 08:27:18 -05:00
hotplug-pci.c PCI: Remove unnecessary __ref annotations 2014-04-29 17:36:44 -06:00
htirq.c x86/htirq: Use hierarchical irqdomain to manage Hypertransport interrupts 2015-04-24 15:36:50 +02:00
iov.c PCI: Add pcibios_iov_resource_alignment() interface 2015-03-31 13:02:36 +11:00
irq.c PCI: Fix whitespace, capitalization, and spelling errors 2013-11-14 11:28:18 -07:00
Kconfig PCI,parisc: Enable 64-bit bus addresses on PA-RISC 2015-09-08 15:30:47 +02:00
Makefile PCI: Build setup-irq.o for arm64 2015-08-20 12:02:49 -05:00
msi.c Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-09-01 14:33:35 -07:00
of.c PCI/MSI: Allow msi_domain lookup using the host bridge node 2015-07-30 00:14:37 +02:00
pci-acpi.c PCI / ACPI: Fix pci_acpi_optimize_delay() comment 2015-07-15 15:11:50 -05:00
pci-driver.c kexec: split kexec_load syscall from kexec core code 2015-09-10 13:29:01 -07:00
pci-label.c PCI: Make a shareable UUID for PCI firmware ACPI _DSM 2015-04-08 14:39:30 -05:00
pci-stub.c PCI: Whitespace cleanup 2014-06-10 20:20:19 -06:00
pci-sysfs.c PCI: Don't read past the end of sysfs "driver_override" buffer 2015-02-24 17:35:37 -06:00
pci.c Merge branch 'x86-mm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-09-01 10:07:40 -07:00
pci.h PCI: Move PCI_FIND_CAP_TTL to pci.h and use it in quirks 2015-07-14 23:35:36 -05:00
probe.c libnvdimm for 4.3: 2015-09-08 14:35:59 -07:00
proc.c PCI: Whitespace cleanup 2014-06-10 20:20:19 -06:00
quirks.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2015-08-31 17:38:39 -07:00
remove.c PCI: Embed ATS info directly into struct pci_dev 2015-08-13 15:57:21 -05:00
rom.c PCI: Fix infinite loop with ROM image of size 0 2015-01-23 17:42:59 -06:00
search.c PCI: Delete unnecessary NULL pointer checks 2014-11-10 21:02:17 -07:00
setup-bus.c PCI: Preserve resource size during alignment reordering 2015-06-01 17:56:32 -05:00
setup-irq.c PCI: Export symbols required for loadable host driver modules 2015-04-08 14:17:10 -05:00
setup-res.c PCI: Mark invalid BARs as unassigned 2015-03-12 18:52:12 -05:00
slot.c PCI: Hold pci_slot_mutex while searching bus->slots list 2015-07-30 16:19:53 -05:00
syscall.c PCI: Whitespace cleanup 2014-06-10 20:20:19 -06:00
vc.c PCI: Use dev->has_secondary_link to find downstream PCIe links 2015-05-29 15:35:26 -05:00
vpd.c
xen-pcifront.c PCI: Use for_each_pci_msi_entry() to access MSI device list 2015-07-22 18:37:43 +02:00