netdev - Re: [PATCH v2] rtw88: Disable PCIe ASPM while doing NAPI poll on 8821CE

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Date:   Tue, 14 Dec 2021 07:46:41 +0200
From:   Kalle Valo <kvalo@...nel.org>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     tony0620emma@...il.com, pkshih@...ltek.com, jian-hong@...lessm.com,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Po-Hao Huang <phhuang@...ltek.com>,
        Brian Norris <briannorris@...omium.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rtw88: Disable PCIe ASPM while doing NAPI poll on 8821CE

Kai-Heng Feng <kai.heng.feng@...onical.com> writes:

> 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>

[...]

>  static bool rtw_disable_msi;
>  static bool rtw_pci_disable_aspm;
> +static int rtw_rx_aspm = -1;
>  module_param_named(disable_msi, rtw_disable_msi, bool, 0644);
>  module_param_named(disable_aspm, rtw_pci_disable_aspm, bool, 0644);
> +module_param_named(rx_aspm, rtw_rx_aspm, int, 0444);
>  MODULE_PARM_DESC(disable_msi, "Set Y to disable MSI interrupt support");
>  MODULE_PARM_DESC(disable_aspm, "Set Y to disable PCI ASPM support");
> +MODULE_PARM_DESC(rx_aspm, "Use PCIe ASPM for RX (0=disable, 1=enable, -1=default)")

We already have disable_aspm parameter, why do we need yet another one?
There's a high bar for new module parameters.

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