linux-kernel - Re: [PATCH v4 8/8] serial: qcom-geni: Rework TX in FIFO mode to fix hangs/lockups

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Message-ID: <CAD=FV=UuChPf0DH7aYq8r2XLCr7D+mbm4QSfthf-9ezvFeNUbg@mail.gmail.com>
Date: Mon, 17 Jun 2024 12:37:46 -0700
From: Doug Anderson <dianders@...omium.org>
To: Konrad Dybcio <konrad.dybcio@...aro.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>, 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>
Subject: Re: [PATCH v4 8/8] serial: qcom-geni: Rework TX in FIFO mode to fix hangs/lockups

Hi,

On Mon, Jun 17, 2024 at 12:10 PM Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
>
>
>
> On 6/11/24 00:24, Douglas Anderson wrote:
> > The fact that the Qualcomm GENI hardware interface is based around
> > "packets" is really awkward to fit into Linux's UART design.
> > Specifically, in order to send bytes you need to start up a new
> > "command" saying how many bytes you want to send and then you need to
> > send all those bytes. Once you've committed to sending that number of
> > bytes it's very awkward to change your mind and send fewer, especially
> > if you want to do so without dropping bytes on the ground.
>
> [...]
>
>
> > +static void qcom_geni_serial_enable_cmd_done(struct uart_port *uport)
> > +{
> > +     struct qcom_geni_serial_port *port = to_dev_port(uport);
> > +
> > +     /* If we're not in FIFO mode we don't use CMD_DONE. */
> > +     if (port->dev_data->mode != GENI_SE_FIFO)
> > +             return;
> > +
> > +     writel(M_CMD_DONE_EN, uport->membase + SE_GENI_M_IRQ_EN_SET);
> > +}
>
> IDK if this is worth of a separate function, instead of checking for the
> FIFO in port_setup and writing it there, but generally this patch looks
> good to me

Sure. Somehow it felt weird to me to put it straight in there, but I
could go either way. Do you think I should spin the series just for
this, or just make this change if I happen to need to spin the series
for something else?


> Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>

Thanks for your reviews, I appreciate it!

-Doug