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From:   Ulf Hansson <ulf.hansson@linaro.org>
Date:   Thu, 14 Jun 2018 10:58:22 +0200
Message-ID: <CAPDyKFqVpfhJf3R3jbXtjGgXf+0pg=9dgALBnxM_bSyBQrQQDQ@mail.gmail.com>
Subject: Re: [PATCH v3 2/7] serdev: add dev_pm_domain_attach|detach()
To:     sean.wang@mediatek.com
Cc:     Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Marcel Holtmann <marcel@holtmann.org>,
        Johan Hedberg <johan.hedberg@gmail.com>,
        devicetree@vger.kernel.org, linux-bluetooth@vger.kernel.org,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        linux-mediatek@lists.infradead.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Rob Herring <robh@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>, linux-serial@vger.kernel.org
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On Thu, 14 Jun 2018 at 09:14, <sean.wang@mediatek.com> wrote:
>
> From: Sean Wang <sean.wang@mediatek.com>
>
> 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@mediatek.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Ulf Hansson <ulf.hansson@linaro.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Jiri Slaby <jslaby@suse.com>
> Cc: linux-serial@vger.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) {

From 4.18 rc1 via commit 919b7308fcc4, dev_pm_domain_attach() will
return better error codes.

I suggest to change the above error path to:
if (ret)
     return ret;

Then continue with the probing below.

> +               ret = sdrv->probe(to_serdev_device(dev));
> +               if (ret)
> +                       dev_pm_domain_detach(dev, true);
> +       }
>
> -       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;
>  }
>
> --
> 2.7.4
>

Otherwise, this makes sense to me!

Kind regards
Uffe