linux-kernel - Re: [PATCH v4 1/1] phy: fsl-imx8-mipi-dphy: Hook into runtime pm

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Date:   Tue, 23 Feb 2021 10:54:42 +0800
From:   Liu Ying <victor.liu@....com>
To:     Guido Günther <agx@...xcpu.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Robert Chiras <robert.chiras@....com>,
        Sam Ravnborg <sam@...nborg.org>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 1/1] phy: fsl-imx8-mipi-dphy: Hook into runtime pm

On Tue, 2021-02-23 at 10:36 +0800, Liu Ying wrote:
> Hi Guido,
> 
> On Mon, 2021-02-22 at 19:38 +0100, Guido Günther wrote:
> > This allows us to shut down the mipi power domain on the imx8. The
> > alternative would be to drop the dphy from the mipi power domain in the
> > SOCs device tree and only have the DSI host controller visible there but
> > since the PD is mostly about the PHY that would defeat it's purpose.
> > 
> > This allows to shut off the power domain hen blanking the LCD panel:
> 
> s/hen/when/
> 
> > pm_genpd_summary before:
> > 
> > domain                          status          slaves
> >     /device                                             runtime status
> > ----------------------------------------------------------------------
> > mipi                            on
> >     /devices/platform/soc@...oc@0:bus@...00000/30a00300.dphy  unsupported
> >     /devices/platform/soc@...oc@0:bus@...00000/30a00000.mipi_dsi  suspended
> > 
> > after:
> > 
> > mipi                            off-0
> >     /devices/platform/soc@...oc@0:bus@...00000/30a00300.dphy  suspended
> >     /devices/platform/soc@...oc@0:bus@...00000/30a00000.mipi_dsi  suspended
> > 
> > Signed-off-by: Guido Günther <agx@...xcpu.org>
> > ---
> >  drivers/phy/freescale/phy-fsl-imx8-mipi-dphy.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/phy/freescale/phy-fsl-imx8-mipi-dphy.c b/drivers/phy/freescale/phy-fsl-imx8-mipi-dphy.c
> > index a95572b397ca..5de175695834 100644
> > --- a/drivers/phy/freescale/phy-fsl-imx8-mipi-dphy.c
> > +++ b/drivers/phy/freescale/phy-fsl-imx8-mipi-dphy.c
> > @@ -14,6 +14,7 @@
> >  #include <linux/of_platform.h>
> >  #include <linux/phy/phy.h>
> >  #include <linux/platform_device.h>
> > +#include <linux/pm_runtime.h>
> >  #include <linux/regmap.h>
> >  
> >  /* DPHY registers */
> > @@ -469,6 +470,8 @@ static int mixel_dphy_probe(struct platform_device *pdev)
> >  
> >  	dev_set_drvdata(dev, priv);
> >  
> > +	pm_runtime_enable(dev);
> > +
> 
> The runtime PM should be disabled if devm_phy_create()
> or devm_of_phy_provider_register() fail.
> 
> Also, I'm just realizing that mixel_dphy_configure() accesses some PHY
> registers, which likely needs the power domain on. However, the
> phy-core doesn't manage the runtime PM for phy_configure(). It looks
> that the NWL DSI bridge driver, which uses the PHY, enables the same
> power domain prior to the PHY configuration. That's probably why
> mixel_dphy_configure() gets power for accessing registers(if really
> needed). So, perhaps, either make phy_configure() manage runtime PM or

Just to be clear, if phy_configure() is touched, be very carefully on
relevant in-tree PHYs.

Liu Ying

>  
> get/put runtime PM in mixel_dphy_configure().
> 
> Regards,
> Liu Ying
> 
> >  	phy = devm_phy_create(dev, np, &mixel_dphy_phy_ops);
> >  	if (IS_ERR(phy)) {
> >  		dev_err(dev, "Failed to create phy %ld\n", PTR_ERR(phy));
> > @@ -481,8 +484,15 @@ static int mixel_dphy_probe(struct platform_device *pdev)
> >  	return PTR_ERR_OR_ZERO(phy_provider);
> >  }
> >  
> > +static int mixel_dphy_remove(struct platform_device *pdev)
> > +{
> > +	pm_runtime_disable(&pdev->dev);
> > +	return 0;
> > +}
> > +
> >  static struct platform_driver mixel_dphy_driver = {
> >  	.probe	= mixel_dphy_probe,
> > +	.remove = mixel_dphy_remove,
> >  	.driver = {
> >  		.name = "mixel-mipi-dphy",
> >  		.of_match_table	= mixel_dphy_of_match,