Re: [PATCH v2 0/3] PCI: Add PCI_ERROR_RESPONSE, check for errors

[Keith Busch <kbusch@kernel.org>]

On Thu, Aug 22, 2019 at 03:05:48PM -0500, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
> 
> Reads from a PCI device may fail if the device has been turned off (put
> into D3cold), removed, or if some other error occurs.  The PCI host bridge
> typically fabricates ~0 data to complete the CPU's read.
> 
> We check for that in a few places, but not in a consistent way.  This
> series adds a PCI_ERROR_RESPONSE definition to make the checks more
> consistent and easier to find.  Note that ~0 may indicate a PCI error, but
> it may also be valid read data, so you need more information (such as
> knowing that a register can never contain ~0) before concluding that it's
> an error.
> 
> This series also adds a new check for PCI_ERROR_RESPONSE in the power
> management code because that code frequently encounters devices in D3cold,
> where we previously misinterpreted ~0 data.  It also uses pci_power_name()
> to print D-state names more consistently.
> 
> Rafael, I didn't add your Reviewed-by to "PCI / PM: Return error when
> changing power state from D3cold" because I made small changes to try to
> make the messages more consistent, and I didn't want to presume they'd be
> OK with you.
> 
> Changes since v1:
>   - Add Rafael's Reviewed-By to the first two patches
>   - Drop "PCI / PM: Check for error when reading PME status" because Rafael
>     pointed out that some devices can signal PME even when in D3cold, so
>     this would require additional rework
>   - Drop "PCI / PM: Check for error when reading Power State" because
>     Rafael thinks it's mostly redundant
> 
> Bjorn Helgaas (3):
>   PCI: Add PCI_ERROR_RESPONSE definition
>   PCI / PM: Decode D3cold power state correctly
>   PCI / PM: Return error when changing power state from D3cold

Series looks good to me.

Reviewed-by: Keith Busch <kbusch@kernel.org>