linux-kernel - Re: [PATCH v1 2/7] serdev: add dev_pm_domain

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Message-Id: <FD85DED4-589C-4113-8A8B-BC5A39494130@holtmann.org>
Date:   Tue, 3 Apr 2018 12:29:31 +0200
From:   Marcel Holtmann <marcel@...tmann.org>
To:     sean.wang@...iatek.com
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Johan Hedberg <johan.hedberg@...il.com>,
        devicetree <devicetree@...r.kernel.org>,
        Bluez mailing list <linux-bluetooth@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-mediatek@...ts.infradead.org,
        LKML <linux-kernel@...r.kernel.org>,
        Rob Herring <robh@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-serial@...r.kernel.org
Subject: Re: [PATCH v1 2/7] serdev: add dev_pm_domain_attach|detach()

Hi Sean,

> In order to open up the required power gate before any operation can be
> effectively performed over the serial bus between CPU and serdev, it's
> clearly essential to add common attach functions for PM domains to serdev
> at the probe phase.
> 
> Similarly, the relevant dettach function for the PM domains should be
> properly and reversely added at the remove phase.
> 
> Signed-off-by: Sean Wang <sean.wang@...iatek.com>
> Cc: Rob Herring <robh@...nel.org>
> Cc: Ulf Hansson <ulf.hansson@...aro.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Jiri Slaby <jslaby@...e.com>
> Cc: linux-serial@...r.kernel.org
> ---
> drivers/tty/serdev/core.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
> index df93b72..c93d8ee 100644
> --- a/drivers/tty/serdev/core.c
> +++ b/drivers/tty/serdev/core.c
> @@ -13,6 +13,7 @@
> #include <linux/module.h>
> #include <linux/of.h>
> #include <linux/of_device.h>
> +#include <linux/pm_domain.h>
> #include <linux/serdev.h>
> #include <linux/slab.h>
> 
> @@ -330,8 +331,16 @@ EXPORT_SYMBOL_GPL(serdev_device_set_tiocm);
> static int serdev_drv_probe(struct device *dev)
> {
> 	const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver);
> +	int ret;
> +
> +	ret = dev_pm_domain_attach(dev, true);
> +	if (ret != -EPROBE_DEFER) {
> +		ret = sdrv->probe(to_serdev_device(dev));
> +		if (ret)
> +			dev_pm_domain_detach(dev, true);
> +	}

so if this is deferred, when does the serdev device gets probed?

> 
> -	return sdrv->probe(to_serdev_device(dev));
> +	return ret;
> }
> 
> static int serdev_drv_remove(struct device *dev)
> @@ -339,6 +348,9 @@ static int serdev_drv_remove(struct device *dev)
> 	const struct serdev_device_driver *sdrv = to_serdev_device_driver(dev->driver);
> 	if (sdrv->remove)
> 		sdrv->remove(to_serdev_device(dev));
> +
> +	dev_pm_domain_detach(dev, true);
> +
> 	return 0;
> }

Regards

Marcel