linux-kernel - Re: [PATCH 6/8] serial: qcom-geni: fix console corruption

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Message-ID: <ZtlyhQ2HNk8unxNI@hovoldconsulting.com>
Date: Thu, 5 Sep 2024 10:57:41 +0200
From: Johan Hovold <johan@...nel.org>
To: Doug Anderson <dianders@...omium.org>
Cc: Johan Hovold <johan+linaro@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Nícolas F . R . A . Prado <nfraprado@...labora.com>,
	linux-arm-msm@...r.kernel.org, linux-serial@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 6/8] serial: qcom-geni: fix console corruption

On Wed, Sep 04, 2024 at 02:51:15PM -0700, Doug Anderson wrote:
> On Mon, Sep 2, 2024 at 8:26 AM Johan Hovold <johan+linaro@...nel.org> wrote:
> >
> > +static void qcom_geni_serial_drain_fifo(struct uart_port *uport)
> > +{
> > +       struct qcom_geni_serial_port *port = to_dev_port(uport);
> > +
> > +       if (!qcom_geni_serial_main_active(uport))
> > +               return;
> 
> It seems like all callers already do the check and only ever call you
> if the port is active. Do you really need to re-check?

I wanted to make the helper self-contained and work in both cases. But
since I ended up only using this helper only in the console code and
will need to move it anyway (under the console ifdef), perhaps I can
consider dropping it. But then again, it's just one register read.

> > @@ -308,6 +311,17 @@ static bool qcom_geni_serial_poll_bit(struct uart_port *uport,
> >         return qcom_geni_serial_poll_bitfield(uport, offset, field, set ? field : 0);
> >  }
> >
> > +static void qcom_geni_serial_drain_fifo(struct uart_port *uport)
> > +{
> > +       struct qcom_geni_serial_port *port = to_dev_port(uport);
> > +
> > +       if (!qcom_geni_serial_main_active(uport))
> > +               return;
> > +
> > +       qcom_geni_serial_poll_bitfield(uport, SE_GENI_M_GP_LENGTH, GP_LENGTH,
> > +                       port->tx_queued);
> 
> nit: indent "port->tx_queued" to match open parenthesis?

No, I don't use open-parenthesis alignment unless that's the
(consistent) style of the code I'm changing (e.g. to avoid unnecessary
realignments when symbol names change and to make a point about
checkpatch --pedantic warnings not being part of the coding style).
 
> ...also: as the kernel test robot reported, w/ certain CONFIGs this is
> defined / not used.

Yes, I need to move the helper under the console ifdef. I was just
waiting to see if there was any further feedback before respinning.

> Aside from the nit / robot issue, this solution looks reasonable to
> me. It's been long enough that I've already paged out much of the past
> digging I did into this driver, but this seems like it should work.
> Feel free to add my Reviewed-by when the robot issue is fixed.

Thanks for reviewing.

Johan