Hi,
sorry for the delay in reviewing. I've wondered for some time what to
make of this series.
Am 17.10.25 um 20:17 schrieb Timothy Pearson:
Certain hardware devices, such as the IBM POWER9 CPU, transparently swap PCI
bus MMIO data endianness when running in big endian mode. This transparent
data swapping presents issues for certain types of BARs, for example little
endian framebuffers, where the device driver needs to be aware the PCI BAR
is now appearing as big endian from the host's perspective.
Introduce CONFIG_PCI_ARCH_ENDIAN_AUTOSWAP and enable on ppc64 systems.
I would not want a config option. In the latest version of the driver,
we have a struct to describe device quirks. [1] I think we should detect
this scenario in the driver and set the quirk if necessary. The
detection can be at compile time though.
If this problem affects many graphics drivers, we can re-evaluate.
[1]
https://gitlab.freedesktop.org/drm/misc/kernel/-/blob/drm-misc-next-2025-11-14/drivers/gpu/drm/ast/ast_drv.h?ref_type=tags#L167
Best regards
Thomas
Signed-off-by: Timothy Pearson <[email protected]>
---
arch/powerpc/Kconfig | 1 +
drivers/pci/Kconfig | 4 ++++
2 files changed, 5 insertions(+)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e24f4d88885a..0e75fe570389 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -314,6 +314,7 @@ config PPC
select OF_EARLY_FLATTREE
select OLD_SIGACTION if PPC32
select OLD_SIGSUSPEND
+ select PCI_ARCH_ENDIAN_AUTOSWAP if PCI && PPC64
select PCI_DOMAINS if PCI
select PCI_MSI_ARCH_FALLBACKS if PCI_MSI
select PCI_SYSCALL if PCI
diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
index 7065a8e5f9b1..fccc01110763 100644
--- a/drivers/pci/Kconfig
+++ b/drivers/pci/Kconfig
@@ -40,6 +40,10 @@ config PCI_DOMAINS_GENERIC
config PCI_SYSCALL
bool
+config PCI_ARCH_ENDIAN_AUTOSWAP
+ bool
+ depends on PCI
+
source "drivers/pci/pcie/Kconfig"
config PCI_MSI
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)
