Re: [PATCH v2 2/2] PCI: Set RCB only when the Root Port has it set

[sashiko-bot@kernel.org]

> pci_configure_rcb() read-modify-writes Link Control of every endpoint
> at enumeration, also when RCB is clear in the Root Port and there is
> nothing to set. Not writing a register that has nothing to change is
> justified on its own, but the write-back of the other Link Control bits
> also has side effects on some devices: the Renesas uPD720201 xHCI
> (1912:0014) comes out of reset with ASPM L0s and L1 enabled and stops
> clearing them itself once Link Control has been written. On a link
> whose Root Port supports no ASPM, the previous patch clears them, but
> it does not run with pcie_aspm=off or CONFIG_PCIEASPM=n. There the
> first access to the xHCI BAR runs into completion timeouts that hang
> the system.
> 
> RCB may only be set in an endpoint if it is set in the Root Port, so
> there is no need to ever clear it here; an endpoint with RCB set
> below a Root Port without it is a firmware configuration error. Only
> set RCB, and only when the Root Port has it set.
> 
> Fixes: 1a6845aaa6de ("PCI: Initialize RCB from pci_configure_device()")
> Cc: stable@vger.kernel.org
> Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Stefan Roese <stefan.roese@mailbox.org>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261002091029.2225203-1-stefan.roese@mailbox.org?part=2