Messages in this thread | | | Subject | Re: [PATCH] mwifiex: Add quirk resetting the PCI bridge on MS Surface devices | From | Kalle Valo <> | Date | Mon, 18 Oct 2021 12:27:24 +0000 (UTC) |
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Jonas Dreßler <verdre@v0yd.nl> wrote:
> The most recent firmware (15.68.19.p21) of the 88W8897 PCIe+USB card > reports a hardcoded LTR value to the system during initialization, > probably as an (unsuccessful) attempt of the developers to fix firmware > crashes. This LTR value prevents most of the Microsoft Surface devices > from entering deep powersaving states (either platform C-State 10 or > S0ix state), because the exit latency of that state would be higher than > what the card can tolerate. > > Turns out the card works just the same (including the firmware crashes) > no matter if that hardcoded LTR value is reported or not, so it's kind > of useless and only prevents us from saving power. > > To get rid of those hardcoded LTR requirements, it's possible to reset > the PCI bridge device after initializing the cards firmware. I'm not > exactly sure why that works, maybe the power management subsystem of the > PCH resets its stored LTR values when doing a function level reset of > the bridge device. Doing the reset once after starting the wifi firmware > works very well, probably because the firmware only reports that LTR > value a single time during firmware startup. > > Signed-off-by: Jonas Dreßler <verdre@v0yd.nl>
I'm not sure what was the conclusion from the discussion, so dropping the patch. Please resend once it's ready to be applied.
Patch set to Changes Requested.
-- https://patchwork.kernel.org/project/linux-wireless/patch/20211011134238.16551-1-verdre@v0yd.nl/
https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
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