On Tue, 2024-10-22 at 17:30 -0500, Bjorn Helgaas wrote:
On Mon, Oct 07, 2024 at 08:59:17AM +0530, Ajay Agarwal wrote:
The current sequence in the driver for L1ss update is as follows.
Disable L1ss Disable L1 Enable L1ss as required Enable L1 if required
With this sequence, a bus hang is observed during the L1ss disable sequence when the RC CPU attempts to clear the RC L1ss register after clearing the EP L1ss register. It looks like the RC attempts to enter L1ss again and at the same time, access to RC L1ss register fails because aux clk is still not active.
PCIe spec r6.2, section 5.5.4, recommends that setting either or both of the enable bits for ASPM L1 PM Substates must be done while ASPM L1 is disabled. My interpretation here is that clearing L1ss should also be done when L1 is disabled. Thereby, change the sequence as follows.
Disable L1 Disable L1ss Enable L1ss as required Enable L1 if required
Signed-off-by: Ajay Agarwal ajayagarwal@google.com
Applied to pci/aspm for v6.13, thank you, Ajay!
Thanks! MediaTek also found this issue will happen on some old kernel, for example 6.11 or 6.12. would you please pick this patch also to some stable tree?
LINK:https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/driv...
Thanks a lot. Macpaul Lin
On Thu, Jun 05, 2025 at 11:23:02AM +0000, Macpaul Lin (林智斌) wrote:
On Tue, 2024-10-22 at 17:30 -0500, Bjorn Helgaas wrote:
On Mon, Oct 07, 2024 at 08:59:17AM +0530, Ajay Agarwal wrote:
The current sequence in the driver for L1ss update is as follows.
Disable L1ss Disable L1 Enable L1ss as required Enable L1 if required
With this sequence, a bus hang is observed during the L1ss disable sequence when the RC CPU attempts to clear the RC L1ss register after clearing the EP L1ss register. It looks like the RC attempts to enter L1ss again and at the same time, access to RC L1ss register fails because aux clk is still not active.
PCIe spec r6.2, section 5.5.4, recommends that setting either or both of the enable bits for ASPM L1 PM Substates must be done while ASPM L1 is disabled. My interpretation here is that clearing L1ss should also be done when L1 is disabled. Thereby, change the sequence as follows.
Disable L1 Disable L1ss Enable L1ss as required Enable L1 if required
Signed-off-by: Ajay Agarwal ajayagarwal@google.com
Applied to pci/aspm for v6.13, thank you, Ajay!
Thanks! MediaTek also found this issue will happen on some old kernel, for example 6.11 or 6.12. would you please pick this patch also to some stable tree?
LINK:https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/driv...
Please submit it properly, with your signed-off-by and we will be glad to consider it.
thanks,
greg k-h
linux-stable-mirror@lists.linaro.org
-
Greg KH -
Macpaul Lin (林智斌)