linux-kernel - Re: [PATCH v4 0/8] serial: qcom-geni: Overhaul TX handling to fix crashes/hangs

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Date: Thu, 20 Jun 2024 19:13:49 -0400
From: Nícolas F. R. A. Prado <nfraprado@...labora.com>
To: Douglas Anderson <dianders@...omium.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Yicong Yang <yangyicong@...ilicon.com>,
	Tony Lindgren <tony@...mide.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Johan Hovold <johan+linaro@...nel.org>,
	John Ogness <john.ogness@...utronix.de>,
	linux-arm-msm@...r.kernel.org,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
	Stephen Boyd <swboyd@...omium.org>, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	Rob Herring <robh@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
	Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
Subject: Re: [PATCH v4 0/8] serial: qcom-geni: Overhaul TX handling to fix
 crashes/hangs

On Mon, Jun 10, 2024 at 03:24:18PM -0700, Douglas Anderson wrote:
> 
> While trying to reproduce -EBUSY errors that our lab was getting in
> suspend/resume testing, I ended up finding a whole pile of problems
> with the Qualcomm GENI serial driver. I've posted a fix for the -EBUSY
> issue separately [1]. This series is fixing all of the Qualcomm GENI
> problems that I found.
> 
> As far as I can tell most of the problems have been in the Qualcomm
> GENI serial driver since inception, but it can be noted that the
> behavior got worse with the new kfifo changes. Previously when the OS
> took data out of the circular queue we'd just spit stale data onto the
> serial port. Now we'll hard lockup. :-P
> 
> I've tried to break this series up as much as possible to make it
> easier to understand but the final patch is still a lot of change at
> once. Hopefully it's OK.
> 
> [1] https://lore.kernel.org/r/20240530084841.v2.1.I2395e66cf70c6e67d774c56943825c289b9c13e4@changeid

Hi,

we've experienced issues with missing kernel messages in the serial on the
sc7180 based platforms in our lab for a while now.

I've just run a batch of jobs that just boot and write some messages to
/dev/kmsg on sc7180-trogdor-lazor-limozeen. Before the patch, in 18 out of
20 runs the first message would be missing in the logs causing the test to fail.
After the patch all 20 runs passed. So this is a clear fix, and I'm very happy
to say goodbye to this issue. Thank you!

Tested-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>

FTR, this is the issue ticket in KernelCI:
https://github.com/kernelci/kernelci-project/issues/380

Thanks,
Nícolas