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Date: Mon, 13 Apr 2020 14:52:57 +0200 From: Marc Kleine-Budde <mkl@...gutronix.de> To: Anson Huang <Anson.Huang@....com>, jassisinghbrar@...il.com, shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org Cc: Linux-imx@....com Subject: Re: [PATCH] mailbox: imx: Support runtime PM On 4/13/20 2:25 PM, Anson Huang wrote: > Some power hungry sub-systems like VPU has its own MUs which also > use mailbox driver, current mailbox driver uses platform driver > model and MU's power will be ON after driver probed and left ON > there, it may cause the whole sub-system can NOT enter lower power > mode, take VPU driver for example, it has runtime PM support, but > due to its MU always ON, the VPU sub-system will be always ON and > consume many power during kernel idle. > > To save power in kernel idle, mailbox driver needs to support > runtime PM in order to power off MU when it is unused. However, > the runtime suspend/resume can ONLY be implemented in mailbox's > .shutdown/.startup callback, so its consumer needs to call > mbox_request_channel()/mbox_free_channel() in consumer driver's > runtime PM callback, then the MU's power will be ON/OFF along with > consumer's runtime PM status. > > Signed-off-by: Anson Huang <Anson.Huang@....com> > --- > drivers/mailbox/imx-mailbox.c | 27 ++++++++++++++++++++++++++- > 1 file changed, 26 insertions(+), 1 deletion(-) > > diff --git a/drivers/mailbox/imx-mailbox.c b/drivers/mailbox/imx-mailbox.c > index 7906624..97bf0ac 100644 > --- a/drivers/mailbox/imx-mailbox.c > +++ b/drivers/mailbox/imx-mailbox.c > @@ -12,6 +12,7 @@ > #include <linux/mailbox_controller.h> > #include <linux/module.h> > #include <linux/of_device.h> > +#include <linux/pm_runtime.h> > #include <linux/slab.h> > > #define IMX_MU_xSR_GIPn(x) BIT(28 + (3 - (x))) > @@ -287,6 +288,7 @@ static int imx_mu_startup(struct mbox_chan *chan) > struct imx_mu_con_priv *cp = chan->con_priv; > int ret; > > + pm_runtime_get_sync(priv->dev); > if (cp->type == IMX_MU_TYPE_TXDB) { > /* Tx doorbell don't have ACK support */ > tasklet_init(&cp->txdb_tasklet, imx_mu_txdb_tasklet, > @@ -323,6 +325,7 @@ static void imx_mu_shutdown(struct mbox_chan *chan) > > if (cp->type == IMX_MU_TYPE_TXDB) { > tasklet_kill(&cp->txdb_tasklet); > + pm_runtime_put_sync(priv->dev); > return; > } > > @@ -341,6 +344,7 @@ static void imx_mu_shutdown(struct mbox_chan *chan) > } > > free_irq(priv->irq, chan); > + pm_runtime_put_sync(priv->dev); > } > > static const struct mbox_chan_ops imx_mu_ops = { > @@ -508,7 +512,27 @@ static int imx_mu_probe(struct platform_device *pdev) > > platform_set_drvdata(pdev, priv); > > - return devm_mbox_controller_register(dev, &priv->mbox); > + ret = devm_mbox_controller_register(dev, &priv->mbox); > + if (ret) > + return ret; > + > + pm_runtime_enable(dev); > + First registering at the system and then setting up the power management looks racy. Don't know if this is serialized by some other means. > + ret = pm_runtime_get_sync(dev); > + if (ret < 0) { > + pm_runtime_put_noidle(dev); > + goto disable_runtime_pm; > + } > + > + ret = pm_runtime_put_sync(dev); > + if (ret < 0) > + goto disable_runtime_pm; > + > + return 0; Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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