linux-kernel - Re: [PATCH v4 7/8] serial: qcom-geni: Fix suspend while active UART xfer

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Message-ID: <ZnqD6ZFxfU6P5yN5@hovoldconsulting.com>
Date: Tue, 25 Jun 2024 10:46:33 +0200
From: Johan Hovold <johan@...nel.org>
To: Doug 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>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v4 7/8] serial: qcom-geni: Fix suspend while active UART
 xfer

On Mon, Jun 24, 2024 at 01:58:34PM -0700, Doug Anderson wrote:
> On Mon, Jun 24, 2024 at 5:12 AM Johan Hovold <johan@...nel.org> wrote:

> > I'm leaning towards fixing the immediate hard lockup regression
> > separately and then we can address the older bugs and rework driver
> > without having to rush things.
> 
> Yeah, that's fair. I've responded to your patch with a
> counter-proposal to fix the hard lockup regression, but I agree that
> should take priority.
> 
> > I've prepared a minimal three patch series which fixes most of the
> > discussed issues (hard and soft lockup and garbage characters) and that
> > should be backportable as well.
> >
> > Currently, the diffstat is just:
> >
> >          drivers/tty/serial/qcom_geni_serial.c | 36 +++++++++++++++++++++++++-----------
> >          1 file changed, 25 insertions(+), 11 deletions(-)
> 
> I'll respond more in dept to your patches, but I suspect that your
> patch series won't fix the issues that Nícolas reported [1]. I also
> tested and your patch series doesn't fix the kdb issue talked about in
> my patch #8. Part of my reworking of stuff also changed the way that
> the console and the polling commands worked since they were pretty
> broken. Your series doesn't touch them.

Right, I never claimed to fix all the issues, only some of the most
obvious and severe ones. 

> We'll probably need something in-between taking advantage of some of
> the stuff you figured out with "cancel" but also doing a bigger rework
> than you did.

Quite likely. My intention was to try to find minimal fixes for
individual issues, which could also be backported, before doing a larger
rework if that turns out to be necessary (and which can also be done in
more than way, e.g. using 16-byte fifos).

Johan