linux-kernel - Re: [PATCH v2 1/1] phy: fsl-imx8-mipi-dphy: Hook into runtime pm

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Date:   Wed, 16 Dec 2020 12:58:36 +0100
From:   Lucas Stach <l.stach@...gutronix.de>
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 v2 1/1] phy: fsl-imx8-mipi-dphy: Hook into runtime pm

Hi Guido,

Am Mittwoch, dem 16.12.2020 um 12:27 +0100 schrieb Guido Günther:
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.

Adding RPM support is exactly the right course of action.

This allows to shut off the power domain hen blanking the LCD panel:

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>
---
 .../phy/freescale/phy-fsl-imx8-mipi-dphy.c    | 22 ++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/drivers/phy/freescale/phy-fsl-imx8-mipi-dphy.c b/drivers/phy/freescale/phy-fsl-imx8-mipi-dphy.c
index a95572b397ca..34e2d801e520 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 */
@@ -93,6 +94,7 @@ struct mixel_dphy_cfg {
 };
 

 struct mixel_dphy_priv {
+	struct device *dev;
 	struct mixel_dphy_cfg cfg;
 	struct regmap *regmap;
 	struct clk *phy_ref_clk;
@@ -382,6 +384,7 @@ static int mixel_dphy_power_on(struct phy *phy)
 	ret = clk_prepare_enable(priv->phy_ref_clk);
 	if (ret < 0)
 		return ret;
+	pm_runtime_get_sync(priv->dev);

This call can fail and will leave you with an elevated rpm refcount.
Better use the new pm_runtime_resume_and_get to avoid this issue? 

Nitpick: I would add a blank line before the call.

Regards,
Lucas

 

 	phy_write(phy, PWR_ON, DPHY_PD_PLL);
 	ret = regmap_read_poll_timeout(priv->regmap, DPHY_LOCK, locked,
@@ -395,6 +398,7 @@ static int mixel_dphy_power_on(struct phy *phy)
 

 	return 0;
 clock_disable:
+	pm_runtime_put(priv->dev);
 	clk_disable_unprepare(priv->phy_ref_clk);
 	return ret;
 }
@@ -406,6 +410,7 @@ static int mixel_dphy_power_off(struct phy *phy)
 	phy_write(phy, PWR_OFF, DPHY_PD_PLL);
 	phy_write(phy, PWR_OFF, DPHY_PD_DPHY);
 

+	pm_runtime_put(priv->dev);
 	clk_disable_unprepare(priv->phy_ref_clk);
 

 	return 0;
@@ -467,6 +472,7 @@ static int mixel_dphy_probe(struct platform_device *pdev)
 	dev_dbg(dev, "phy_ref clock rate: %lu\n",
 		clk_get_rate(priv->phy_ref_clk));
 

+	priv->dev = dev;
 	dev_set_drvdata(dev, priv);
 

 	phy = devm_phy_create(dev, np, &mixel_dphy_phy_ops);
@@ -477,12 +483,26 @@ static int mixel_dphy_probe(struct platform_device *pdev)
 	phy_set_drvdata(phy, priv);
 

 	phy_provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
+	if (IS_ERR(phy_provider))
+		return PTR_ERR(phy_provider);
 

-	return PTR_ERR_OR_ZERO(phy_provider);
+	pm_runtime_enable(dev);
+
+	return 0;
+}
+
+static int mixel_dphy_remove(struct platform_device *pdev)
+{
+	struct mixel_dphy_priv *priv = platform_get_drvdata(pdev);
+
+	pm_runtime_disable(priv->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,