Re: [PATCH 3/4] tty: serial: 8250_mtk: use pm_runtime callbacks for enabling

From: Sascha Hauer <s.hauer@pengutronix.de>
To: Matthias Brugger <matthias.bgg@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	linux-mediatek@lists.infradead.org,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	linux-serial@vger.kernel.org, Alan Cox <alan@linux.intel.com>
Subject: Re: [PATCH 3/4] tty: serial: 8250_mtk: use pm_runtime callbacks for enabling
Date: Mon, 4 May 2015 14:06:51 +0200	[thread overview]
Message-ID: <20150504120651.GR6325@pengutronix.de> (raw)
In-Reply-To: <CABuKBeJwduxLuyXcy7Ho+k+_Ye3+nHiGvdr8vTFsJzdHDBQPSA@mail.gmail.com>

On Mon, May 04, 2015 at 01:05:27PM +0200, Matthias Brugger wrote:
> 2015-04-27 8:49 GMT+02:00 Sascha Hauer <s.hauer@pengutronix.de>:
> > The pm_runtime callbacks already enable and disable the device.
> > Use them in probe() and remove() instead of duplicating the
> > code. This allows us to concentrate more code for enabling/disabling
> > the UART in a single place.
> >
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  drivers/tty/serial/8250/8250_mtk.c | 69 ++++++++++++++++++++------------------
> >  1 file changed, 36 insertions(+), 33 deletions(-)
> >
> > diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
> > index bcfaa8dc..2f28bd0 100644
> > --- a/drivers/tty/serial/8250/8250_mtk.c
> > +++ b/drivers/tty/serial/8250/8250_mtk.c
> > @@ -115,6 +115,29 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios,
> >                 tty_termios_encode_baud_rate(termios, baud, baud);
> >  }
> >
> > +static int mtk8250_runtime_suspend(struct device *dev)
> > +{
> > +       struct mtk8250_data *data = dev_get_drvdata(dev);
> > +
> > +       clk_disable_unprepare(data->uart_clk);
> > +
> > +       return 0;
> > +}
> > +
> > +static int mtk8250_runtime_resume(struct device *dev)
> > +{
> > +       struct mtk8250_data *data = dev_get_drvdata(dev);
> > +       int err;
> > +
> > +       err = clk_prepare_enable(data->uart_clk);
> > +       if (err) {
> > +               dev_warn(dev, "Can't enable clock\n");
> > +               return err;
> > +       }
> > +
> > +       return 0;
> > +}
> > +
> >  static void
> >  mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
> >  {
> > @@ -130,19 +153,12 @@ mtk8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old)
> >  static int mtk8250_probe_of(struct platform_device *pdev, struct uart_port *p,
> >                            struct mtk8250_data *data)
> >  {
> > -       int err;
> > -
> >         data->uart_clk = devm_clk_get(&pdev->dev, NULL);
> >         if (IS_ERR(data->uart_clk)) {
> >                 dev_warn(&pdev->dev, "Can't get uart clock\n");
> >                 return PTR_ERR(data->uart_clk);
> >         }
> >
> > -       err = clk_prepare_enable(data->uart_clk);
> > -       if (err) {
> > -               dev_warn(&pdev->dev, "Can't prepare clock\n");
> > -               return err;
> > -       }
> >         p->uartclk = clk_get_rate(data->uart_clk);
> >
> >         return 0;
> > @@ -193,14 +209,18 @@ static int mtk8250_probe(struct platform_device *pdev)
> >         writel(0x0, uart.port.membase +
> >                         (MTK_UART_RATE_FIX << uart.port.regshift));
> >
> > -       data->line = serial8250_register_8250_port(&uart);
> > -       if (data->line < 0)
> > -               return data->line;
> > -
> >         platform_set_drvdata(pdev, data);
> >
> > -       pm_runtime_set_active(&pdev->dev);
> >         pm_runtime_enable(&pdev->dev);
> > +       if (!pm_runtime_enabled(&pdev->dev)) {
> > +               err = mtk8250_runtime_resume(&pdev->dev);
> > +               if (err)
> > +                       return err;
> > +       }
> > +
> > +       data->line = serial8250_register_8250_port(&uart);
> > +       if (data->line < 0)
> > +               return data->line;
> 
> Why do you delete pm_runtime_set_active here?

pm_runtime_set_active() communicates the initial state of the device to
the pm core. Previously the driver activated the device manually by
directly calling clk_prepare_enable(). Since this manual enabling of
the clock is removed in this patch, the device is no longer active,
hence pm_runtime_set_active() has to be removed.

Sascha

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