netdev - Re: [PATCH] ath10k: Introduce a devicetree quirk to skip host cap QMI requests

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Date:   Thu, 29 Oct 2020 08:40:17 -0500
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Amit Pundir <amit.pundir@...aro.org>,
        Kalle Valo <kvalo@...eaurora.org>,
        David S Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Jeffrey Hugo <jeffrey.l.hugo@...il.com>,
        John Stultz <john.stultz@...aro.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Konrad Dybcio <konradybcio@...il.com>,
        ath10k@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ath10k: Introduce a devicetree quirk to skip host cap
 QMI requests

On Tue 29 Sep 14:08 CDT 2020, Rob Herring wrote:

> On Fri, Sep 25, 2020 at 11:59:41PM +0530, Amit Pundir wrote:
> > There are firmware versions which do not support host capability
> > QMI request. We suspect either the host cap is not implemented or
> > there may be firmware specific issues, but apparently there seem
> > to be a generation of firmware that has this particular behavior.
> > 
> > For example, firmware build on Xiaomi Poco F1 (sdm845) phone:
> > "QC_IMAGE_VERSION_STRING=WLAN.HL.2.0.c3-00257-QCAHLSWMTPLZ-1"
> > 
> > If we do not skip the host cap QMI request on Poco F1, then we
> > get a QMI_ERR_MALFORMED_MSG_V01 error message in the
> > ath10k_qmi_host_cap_send_sync(). But this error message is not
> > fatal to the firmware nor to the ath10k driver and we can still
> > bring up the WiFi services successfully if we just ignore it.
> > 
> > Hence introducing this DeviceTree quirk to skip host capability
> > QMI request for the firmware versions which do not support this
> > feature.
> 
> So if you change the WiFi firmware, you may force a DT change too. Those 
> are pretty independent things otherwise.
> 

Yes and that's not good. But I looked at somehow derive this from
firmware version numbers etc and it's not working out, so I'm out of
ideas for alternatives.

> Why can't you just always ignore this error? If you can't deal with this 
> entirely in the driver, then it should be part of the WiFi firmware so 
> it's always in sync.
> 

Unfortunately the firmware versions I've hit this problem on has gone
belly up when receiving this request, that's why I asked Amit to add a
flag to skip it.

That said, in the devices I've hit this I've managed to get newer
firmware working, which doesn't have either problem.

Regards,
Bjorn