linux-kernel - Re: [PATCH v4] rtw88: Disable PCIe ASPM while doing NAPI poll on 8821CE

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Date:   Wed, 15 Dec 2021 12:23:07 +0000
From:   Pkshih <pkshih@...ltek.com>
To:     "kai.heng.feng@...onical.com" <kai.heng.feng@...onical.com>,
        "tony0620emma@...il.com" <tony0620emma@...il.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "jian-hong@...lessm.com" <jian-hong@...lessm.com>,
        "kvalo@...eaurora.org" <kvalo@...eaurora.org>,
        Bernie Huang <phhuang@...ltek.com>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "briannorris@...omium.org" <briannorris@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] rtw88: Disable PCIe ASPM while doing NAPI poll on 8821CE

On Wed, 2021-12-15 at 19:46 +0800, Kai-Heng Feng wrote:
> Many Intel based platforms face system random freeze after commit
> 9e2fd29864c5 ("rtw88: add napi support").
> 
> The commit itself shouldn't be the culprit. My guess is that the 8821CE
> only leaves ASPM L1 for a short period when IRQ is raised. Since IRQ is
> masked during NAPI polling, the PCIe link stays at L1 and makes RX DMA
> extremely slow. Eventually the RX ring becomes messed up:
> [ 1133.194697] rtw_8821ce 0000:02:00.0: pci bus timeout, check dma status
> 
> Since the 8821CE hardware may fail to leave ASPM L1, manually do it in
> the driver to resolve the issue.
> 
> Fixes: 9e2fd29864c5 ("rtw88: add napi support")
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215131
> BugLink: https://bugs.launchpad.net/bugs/1927808
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>

Reviewed-and-Tested-by: Ping-Ke Shih <pkshih@...ltek.com>

> ---
> v4:
>  - Rebase to the right tree.
> 
> v3:
>  - Move the module parameter to be part of private struct.
>  - Ensure link_usage never goes below zero.
> 
> v2:
>  - Add default value for module parameter.
> 
>  drivers/net/wireless/realtek/rtw88/pci.c | 70 +++++++-----------------
>  drivers/net/wireless/realtek/rtw88/pci.h |  2 +
>  2 files changed, 21 insertions(+), 51 deletions(-)
> 
> 

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