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From:   Alexander Stein <alexander.stein@ew.tq-group.com>
To:     dri-devel@lists.freedesktop.org
Cc:     marex@denx.de, Neil Armstrong <neil.armstrong@linaro.org>,
        Robert Foss <rfoss@kernel.org>,
        Jonas Karlman <jonas@kwiboo.se>, aford@beaconembedded.com,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        linux-kernel@vger.kernel.org,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Chen-Yu Tsai <wenst@chromium.org>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Adam Ford <aford173@gmail.com>,
        Jagan Teki <jagan@amarulasolutions.com>,
        Adam Ford <aford173@gmail.com>
Subject: Re: [PATCH V3 3/7] drm: bridge: samsung-dsim: Fetch pll-clock-frequency automatically
Date:   Thu, 04 May 2023 11:21:30 +0200
Message-ID: <7519081.EvYhyI6sBW@steina-w>
Organization: TQ-Systems GmbH
In-Reply-To: <20230502010759.17282-4-aford173@gmail.com>
References: <20230502010759.17282-1-aford173@gmail.com> <20230502010759.17282-4-aford173@gmail.com>
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Am Dienstag, 2. Mai 2023, 03:07:55 CEST schrieb Adam Ford:
> Make the pll-clock-frequency optional.  If it's present, use it
> to maintain backwards compatibility with existing hardware.  If it
> is absent, read clock rate of "sclk_mipi" to determine the rate.
>=20
> Signed-off-by: Adam Ford <aford173@gmail.com>
> Tested-by: Chen-Yu Tsai <wenst@chromium.org>
> ---
>  drivers/gpu/drm/bridge/samsung-dsim.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>=20
> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c
> b/drivers/gpu/drm/bridge/samsung-dsim.c index bf4b33d2de76..2dc02a9e37c0
> 100644
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -1726,12 +1726,20 @@ static int samsung_dsim_parse_dt(struct samsung_d=
sim
> *dsi) {
>  	struct device *dev =3D dsi->dev;
>  	struct device_node *node =3D dev->of_node;
> +	struct clk *pll_clk;
>  	int ret;
>=20
>  	ret =3D samsung_dsim_of_read_u32(node, "samsung,pll-clock-frequency",
>  				       &dsi->pll_clk_rate);
> -	if (ret < 0)
> -		return ret;
> +
> +	/* If it doesn't exist, read it from the clock instead of failing */
> +	if (ret < 0) {
> +		pll_clk =3D devm_clk_get(dev, "sclk_mipi");
> +		if (!IS_ERR(pll_clk))
> +			dsi->pll_clk_rate =3D clk_get_rate(pll_clk);
> +		else
> +			return PTR_ERR(pll_clk);
> +	}
>=20

Now that 'samsung,pll-clock-frequency' is optional the error in=20
samsung_dsim_of_read_u32() should be changed. Otherwise you will get
> /soc@0/bus@32c00000/dsi@32e10000: failed to get 'samsung,pll-clock-
frequency' property

Best regards,
Alexander

>  	ret =3D samsung_dsim_of_read_u32(node, "samsung,burst-clock-
frequency",
>  				       &dsi->burst_clk_rate);


=2D-=20
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