Re: [PATCH] bus: mhi: pci_generic: increase timeout value for operations to 24000ms

From: Thomas Perrot <thomas.perrot@bootlin.com>
To: Aleksander Morgado <aleksander@aleksander.es>,
	Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	hemantk@codeaurora.org, Loic Poulain <loic.poulain@linaro.org>,
	stable <stable@vger.kernel.org>
Subject: Re: [PATCH] bus: mhi: pci_generic: increase timeout value for operations to 24000ms
Date: Thu, 30 Sep 2021 10:07:57 +0200	[thread overview]
Message-ID: <54c063613fe63282a1c26b312c772e89b662eae6.camel@bootlin.com> (raw)
In-Reply-To: <CAAP7ucL1Zv6g8G0SWAjEAjr6OSVTyDmvmFkH+vMmmBwOH2=ZUQ@mail.gmail.com>

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Hello,

On Wed, 2021-09-29 at 15:17 +0200, Aleksander Morgado wrote:
> Hey Mani,
> 
> > > > diff --git a/drivers/bus/mhi/pci_generic.c
> > > > b/drivers/bus/mhi/pci_generic.c
> > > > index 4dd1077354af..e08ed6e5031b 100644
> > > > --- a/drivers/bus/mhi/pci_generic.c
> > > > +++ b/drivers/bus/mhi/pci_generic.c
> > > > @@ -248,7 +248,7 @@ static struct mhi_event_config
> > > > modem_qcom_v1_mhi_events[] = {
> > > > 
> > > >   static const struct mhi_controller_config
> > > > modem_qcom_v1_mhiv_config = {
> > > >      .max_channels = 128,
> > > > -    .timeout_ms = 8000,
> > > > +    .timeout_ms = 24000,
> > > 
> > > 
> > > This modem_qcom_v1_mhiv_config config applies to all generic SDX24,
> > > SDX55 and SDX65 modules.
> > > Other vendor-branded SDX55 based modules in this same file (Foxconn
> > > SDX55, MV31), have 20000ms as timeout.
> > > Other vendor-branded SDX24 based modules in this same file (Quectel
> > > EM12xx), have also 20000ms as timeout.
> > > Maybe it makes sense to have a common timeout for all?
> > > 
> > 
> > Eventhough the baseport coming from Qualcomm for the modem chipsets
> > are same, it is possible that the vendors might have customized the
> > firmware for their own usecase. That could be the cause of the delay
> > for modem booting.
> > 
> > So I don't think we should use the same timeout of 2400ms for all
> > modems.
> > 
> 
> Please note it's 24000ms what's being suggested here, not 2400ms.
> 
> > > Thomas, is the 24000ms value taken from experimentation, or is it a
> > > safe enough value? Maybe 20000ms as in other modules would have
> > > been enough?
> > > 

I made experimentation on a Sierra EM9190 (SDX55) engineering sample,
using a old development firmware.

So, I agree that setting the same timeout of 24000ms for all modems, is
not necessarily relevant.
However, the current default value seems too low, in view of timeouts
used on vendor-branded, then using a higher value seems relevant.

Moreover, Sierra EM919x modems use a custom controller configuration,
we are currently working on it. As our tests not being sufficiently
conclusive, so we have not yet submitted.

Best regards,
Thomas

> > 
> > It was derived from testing I believe.
> 
> Following your reasoning above, shouldn't this 24000ms timeout be
> applied only to the Sierra Wireless EM91xx devices (which may have
> custom firmware bits delaying the initialization a bit longer), and
> not to the generic SDX24, SDX55 and SDX65?
> 
> If I'm not mistaken, Thomas is testing with a custom mhi_pci_generic
> entry for the EM91xx; as in
> https://forum.sierrawireless.com/t/sierra-wireless-airprime-em919x-pcie-support/24927
> .
> I'm also playing with that same entry on my own setup, but have other
> problems of my own :)
> 
> 
> --
> Aleksander
> https://aleksander.es

-- 
Thomas Perrot, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com

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