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

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Date:   Tue, 14 Dec 2021 14:03:39 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Kalle Valo <kvalo@...nel.org>
Cc:     tony0620emma@...il.com, pkshih@...ltek.com, jhp@...lessos.org,
        "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

On Tue, Dec 14, 2021 at 1:46 PM Kalle Valo <kvalo@...nel.org> wrote:
>
> 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.

It's a good way for (un)affected users to try out different settings.
But yes the parameter isn't necessary. Let me send another version without it.

Kai-Heng

>
> --
> https://patchwork.kernel.org/project/linux-wireless/list/
>
> https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches