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SubjectRe: [PATCH] mailbox: imx: Support runtime PM
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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@nxp.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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