linux-kernel - Re: [PATCH 1/3] drm/bridge: ti-sn65dsi86: Simplify refclk handling

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Message-ID: <CAG3jFyuUodAKJJ2nkQ=JNRgxDPj99jMkJNrCetfbyb_35CWxYA@mail.gmail.com>
Date:   Fri, 5 Mar 2021 11:00:38 +0100
From:   Robert Foss <robert.foss@...aro.org>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sam Ravnborg <sam@...nborg.org>,
        Stephen Boyd <swboyd@...omium.org>,
        MSM <linux-arm-msm@...r.kernel.org>, robdclark@...omium.org,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] drm/bridge: ti-sn65dsi86: Simplify refclk handling

Hey Douglas,

Thanks for submitting this cleanup, it looks good to me.

Reviewed-by: Robert Foss <robert.foss@...aro.org>


On Fri, 5 Mar 2021 at 00:53, Douglas Anderson <dianders@...omium.org> wrote:
>
> The clock framework makes it simple to deal with an optional clock.
> You can call clk_get_optional() and if the clock isn't specified it'll
> just return NULL without complaint. It's valid to pass NULL to
> enable/disable/prepare/unprepare. Let's make use of this to simplify
> things a tiny bit.
>
> NOTE: this makes things look a tad bit asymmetric now since we check
> for NULL before clk_prepare_enable() but not for
> clk_disable_unprepare(). This seemed OK to me. We already have to
> check for NULL in the enable case anyway so why not avoid the extra
> call?

I think this is fine. Since the refclk != NULL check in
ti_sn_bridge_set_refclk_freq is in order to determine other behaviour,
the asymmetry is required.

>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
>
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 11 +++--------
>  1 file changed, 3 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index f27306c51e4d..942019842ff4 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -1261,14 +1261,9 @@ static int ti_sn_bridge_probe(struct i2c_client *client,
>                 return ret;
>         }
>
> -       pdata->refclk = devm_clk_get(pdata->dev, "refclk");
> -       if (IS_ERR(pdata->refclk)) {
> -               ret = PTR_ERR(pdata->refclk);
> -               if (ret == -EPROBE_DEFER)
> -                       return ret;
> -               DRM_DEBUG_KMS("refclk not found\n");
> -               pdata->refclk = NULL;
> -       }
> +       pdata->refclk = devm_clk_get_optional(pdata->dev, "refclk");
> +       if (IS_ERR(pdata->refclk))
> +               return PTR_ERR(pdata->refclk);
>
>         ret = ti_sn_bridge_parse_dsi_host(pdata);
>         if (ret)
> --
> 2.30.1.766.gb4fecdf3b7-goog
>