Just a gentle ping. If there are still problems with this patch,
please let me know. Thank you.



On Thu, Jul 22, 2021 at 10:21 AM Vincent Chen [off-list ref] wrote:

On Wed, Jul 21, 2021 at 1:57 PM Christoph Hellwig [off-list ref] wrote:

quoted

On Wed, Jul 21, 2021 at 11:39:12AM +0800, Vincent Chen wrote:

quoted

The CONFIG_PCI_MSI is used to allow device drivers to enable MSI. The MSI
enables a device to generate an interrupt using an inbound Memory Write
on its PCI bus instead of asserting a device IRQ pin. The whole mechanism
needs support from the PCI controller or generic interrupt controller and
the corresponding software driver.

The RISC-V Kconfig file actively selects the PCI_MSI  if users enable
CONFIG_PCI. However, the RISC-V specification does not require every RISC-V
platform shall have MSI support. In other words, Kconfig enables CONFIG_PCI
to allow PCI devices to use MSI, but due to lack of MSI support, the kernel
may not have any function to deal with the MSI from PCI devices. When this
case happens, it leads to the following warning message displayed in
booting a v5.10~v5.12 kernel.

So make sure the runtime detection works fine.  An x86 kernel with
CONFIG_PCI_MSI also works on non-MSI systems.

NAK to this patch.

Thanks for your information. I think this will be a good reference to
solve this warning message for the v5.10~v5.12 riscv kernel. However,
the current RISC-V does not specify that each platform must have a
controller to support PCI_MSI. Even there is no a ratified
specification to provide an interrupt controller to support MSI. In
this circumstance, removing the CONFIG_PCI_MSI selection from the
Kconfig file seems to more close to the RISC-V platform setting. I
guess that is why most architectures, such as ARM and x86, do not add
"select PCI_MSI if PCI" to their Kconfig file. Therefore, I prefer to
remove the "select PCI_MSI if PCI" from the Kconfig file. Please
correct me if I have misunderstands.

Thank you.

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