linux-kernel - Re: [PATCH v2 2/2] soc: qcom: pmic_glink: Handle GLINK intent allocation rejections

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Message-ID: <b7jydfdsyhn4xhrydsxmjayzvp3t3rwwrgnb45jzektbhotlmm@4czvpsdsjv4f>
Date: Thu, 24 Oct 2024 12:49:29 -0500
From: Bjorn Andersson <andersson@...nel.org>
To: Johan Hovold <johan@...nel.org>
Cc: Bjorn Andersson <bjorn.andersson@....qualcomm.com>, 
	Mathieu Poirier <mathieu.poirier@...aro.org>, Chris Lew <quic_clew@...cinc.com>, 
	Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org, 
	Bjorn Andersson <quic_bjorande@...cinc.com>, linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	stable@...r.kernel.org, Johan Hovold <johan+linaro@...nel.org>
Subject: Re: [PATCH v2 2/2] soc: qcom: pmic_glink: Handle GLINK intent
 allocation rejections

On Thu, Oct 24, 2024 at 08:39:25AM GMT, Johan Hovold wrote:
> On Wed, Oct 23, 2024 at 05:24:33PM +0000, Bjorn Andersson wrote:
> > Some versions of the pmic_glink firmware does not allow dynamic GLINK
> > intent allocations, attempting to send a message before the firmware has
> > allocated its receive buffers and announced these intent allocations
> > will fail.
> 
> > Retry the send until intent buffers becomes available, or an actual
> > error occur.
> 
> > Reported-by: Johan Hovold <johan@...nel.org>
> > Closes: https://lore.kernel.org/all/Zqet8iInnDhnxkT9@hovoldconsulting.com/#t
> > Cc: stable@...r.kernel.org # rpmsg: glink: Handle rejected intent request better
> > Fixes: 58ef4ece1e41 ("soc: qcom: pmic_glink: Introduce base PMIC GLINK driver")
> > Tested-by: Johan Hovold <johan+linaro@...nel.org>
> > Reviewed-by: Johan Hovold <johan+linaro@...nel.org>
> > Signed-off-by: Bjorn Andersson <bjorn.andersson@....qualcomm.com>
> 
> Thanks for the update. Still works as intended here.
> 

Thanks for the confirmation.

> >  int pmic_glink_send(struct pmic_glink_client *client, void *data, size_t len)
> >  {
> >  	struct pmic_glink *pg = client->pg;
> > +	bool timeout_reached = false;
> > +	unsigned long start;
> >  	int ret;
> >  
> >  	mutex_lock(&pg->state_lock);
> > -	if (!pg->ept)
> > +	if (!pg->ept) {
> >  		ret = -ECONNRESET;
> > -	else
> > -		ret = rpmsg_send(pg->ept, data, len);
> > +	} else {
> > +		start = jiffies;
> > +		for (;;) {
> > +			ret = rpmsg_send(pg->ept, data, len);
> > +			if (ret != -EAGAIN)
> > +				break;
> > +
> > +			if (timeout_reached) {
> > +				ret = -ETIMEDOUT;
> > +				break;
> > +			}
> > +
> > +			usleep_range(1000, 5000);
> 
> I ran some quick tests of this patch this morning (reproducing the issue
> five times), and with the above delay it seems a single resend is
> enough. Dropping the delay I once hit:
> 
> [    8.723479] qcom_pmic_glink pmic-glink: pmic_glink_send - resend
> [    8.723877] qcom_pmic_glink pmic-glink: pmic_glink_send - resend
> [    8.723921] qcom_pmic_glink pmic-glink: pmic_glink_send - resend
> [    8.723951] qcom_pmic_glink pmic-glink: pmic_glink_send - resend
> [    8.723981] qcom_pmic_glink pmic-glink: pmic_glink_send - resend
> [    8.724010] qcom_pmic_glink pmic-glink: pmic_glink_send - resend
> [    8.724046] qcom_pmic_glink pmic-glink: pmic_glink_send - resend
> 
> which seems to suggest that a one millisecond sleep is sufficient for
> the currently observed issue.
> 
> It would still mean up to 5k calls if you ever try to send a too large
> buffer or similar and spin here for five seconds however. Perhaps
> nothing to worry about at this point, but increasing the delay or
> lowering the timeout could be considered.
> 

I did consider this as well, but this code-path is specific to
pmic-glink, so we shouldn't have any messages of size unexpected to the
other side...

If we do, then let's fix that. If I'm wrong in my assumptions, I'd be
happy to see this corrected, without my arbitrarily chosen timeout
values.

Thanks,
Bjorn

> > +			timeout_reached = time_after(jiffies, start + PMIC_GLINK_SEND_TIMEOUT);
> > +		}
> > +	}
> >  	mutex_unlock(&pg->state_lock);
> >  
> >  	return ret;
> 
> Johan