On Thu, May 19, 2022 at 01:47:51PM +0200, Marek Vasut wrote:
> The Refclk may be supplied by SoC clock output instead of crystal
> oscillator, make sure the clock are enabled before any other action
> is performed with the bridge chip, otherwise it may either fail to
> operate at all, or miss reset GPIO toggle.
>
> Fixes: 7caff0fc4296e ("drm/bridge: tc358767: Add DPI to eDP bridge driver")
> Signed-off-by: Marek Vasut <marex@xxxxxxx>
> Cc: Jonas Karlman <jonas@xxxxxxxxx>
> Cc: Laurent Pinchart <Laurent.pinchart@xxxxxxxxxxxxxxxx>
> Cc: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> Cc: Marek Vasut <marex@xxxxxxx>
> Cc: Maxime Ripard <maxime@xxxxxxxxxx>
> Cc: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> Cc: Robert Foss <robert.foss@xxxxxxxxxx>
> Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
> ---
> V2: Use devm_add_action_or_reset() to add clock disable hook instead
> of wall of failpath
> ---
> drivers/gpu/drm/bridge/tc358767.c | 30 +++++++++++++++++++++++-------
> 1 file changed, 23 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index 45ea829d56601..b2ef01303be23 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -2033,6 +2033,13 @@ static int tc_probe_bridge_endpoint(struct tc_data *tc)
> return -EINVAL;
> }
>
> +static void tc_clk_disable(void *data)
> +{
> + struct clk *refclk = data;
> +
> + clk_disable_unprepare(refclk);
> +}
> +
> static int tc_probe(struct i2c_client *client, const struct i2c_device_id *id)
> {
> struct device *dev = &client->dev;
> @@ -2049,6 +2056,22 @@ static int tc_probe(struct i2c_client *client, const struct i2c_device_id *id)
> if (ret)
> return ret;
>
> + tc->refclk = devm_clk_get(dev, "ref");
> + if (IS_ERR(tc->refclk)) {
> + ret = PTR_ERR(tc->refclk);
> + dev_err(dev, "Failed to get refclk: %d\n", ret);
> + return ret;
> + }
> +
> + ret = devm_add_action_or_reset(dev, tc_clk_disable, tc->refclk);
> + if (ret)
> + return ret;
if devm_add_action_or_reset fails, tc_clk_disable will be called
resulting in an unbalanced enable count for refclk. it should be called
after the clk_prepare_enable() call.
Maxime
