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.
Since it can be optional, change the message from an error to
dev_info.

Signed-off-by: Adam Ford <aford173@gmail.com>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index bf4b33d2de76..08266303c261 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1712,11 +1712,11 @@ static const struct mipi_dsi_host_ops samsung_dsim_ops = {
 };
 
 static int samsung_dsim_of_read_u32(const struct device_node *np,
-				    const char *propname, u32 *out_value)
+				    const char *propname, u32 *out_value, bool optional)
 {
 	int ret = of_property_read_u32(np, propname, out_value);
 
-	if (ret < 0)
+	if (ret < 0 && !optional)
 		pr_err("%pOF: failed to get '%s' property\n", np, propname);
 
 	return ret;
@@ -1726,20 +1726,29 @@ static int samsung_dsim_parse_dt(struct samsung_dsim *dsi)
 {
 	struct device *dev = dsi->dev;
 	struct device_node *node = dev->of_node;
+	struct clk *pll_clk;
 	int ret;
 
 	ret = samsung_dsim_of_read_u32(node, "samsung,pll-clock-frequency",
-				       &dsi->pll_clk_rate);
-	if (ret < 0)
-		return ret;
+				       &dsi->pll_clk_rate, 1);
+
+	/* If it doesn't exist, read it from the clock instead of failing */
+	if (ret < 0) {
+		dev_info(dev, "Using sclk_mipi for pll clock frequency\n");
+		pll_clk = devm_clk_get(dev, "sclk_mipi");
+		if (!IS_ERR(pll_clk))
+			dsi->pll_clk_rate = clk_get_rate(pll_clk);
+		else
+			return PTR_ERR(pll_clk);
+	}
 
 	ret = samsung_dsim_of_read_u32(node, "samsung,burst-clock-frequency",
-				       &dsi->burst_clk_rate);
+				       &dsi->burst_clk_rate, 0);
 	if (ret < 0)
 		return ret;
 
 	ret = samsung_dsim_of_read_u32(node, "samsung,esc-clock-frequency",
-				       &dsi->esc_clk_rate);
+				       &dsi->esc_clk_rate, 0);
 	if (ret < 0)
 		return ret;
 
-- 
2.39.2

On Tue, May 16, 2023 at 5:27 AM Adam Ford <aford173@gmail.com> wrote:
>
> 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.
> Since it can be optional, change the message from an error to
> dev_info.
>
> Signed-off-by: Adam Ford <aford173@gmail.com>
> Tested-by: Chen-Yu Tsai <wenst@chromium.org>
> Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> ---

Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com> # imx8mm-icore

Hi Adam,

Am Montag, dem 15.05.2023 um 18:57 -0500 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.
> Since it can be optional, change the message from an error to
> dev_info.
> 
> Signed-off-by: Adam Ford <aford173@gmail.com>
> Tested-by: Chen-Yu Tsai <wenst@chromium.org>
> Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> ---
>  drivers/gpu/drm/bridge/samsung-dsim.c | 23 ++++++++++++++++-------
>  1 file changed, 16 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> index bf4b33d2de76..08266303c261 100644
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -1712,11 +1712,11 @@ static const struct mipi_dsi_host_ops samsung_dsim_ops = {
>  };
>  
>  static int samsung_dsim_of_read_u32(const struct device_node *np,
> -				    const char *propname, u32 *out_value)
> +				    const char *propname, u32 *out_value, bool optional)
>  {
>  	int ret = of_property_read_u32(np, propname, out_value);
>  
> -	if (ret < 0)
> +	if (ret < 0 && !optional)
>  		pr_err("%pOF: failed to get '%s' property\n", np, propname);
>  
>  	return ret;
> @@ -1726,20 +1726,29 @@ static int samsung_dsim_parse_dt(struct samsung_dsim *dsi)
>  {
>  	struct device *dev = dsi->dev;
>  	struct device_node *node = dev->of_node;
> +	struct clk *pll_clk;
>  	int ret;
>  
>  	ret = samsung_dsim_of_read_u32(node, "samsung,pll-clock-frequency",
> -				       &dsi->pll_clk_rate);
> -	if (ret < 0)
> -		return ret;
> +				       &dsi->pll_clk_rate, 1);
> +
> +	/* If it doesn't exist, read it from the clock instead of failing */
> +	if (ret < 0) {
> +		dev_info(dev, "Using sclk_mipi for pll clock frequency\n");

While this is certainly helpful while debugging the driver, I don't
think it warrants a info print. Remove or downgrade to dev_dbg?

On the other hand the changed driver behavior should be documented in
the devicetree binding by moving "samsung,pll-clock-frequency" into the
optional properties and spelling out which clock rate is used when the
property is absent.

Regards,
Lucas

> +		pll_clk = devm_clk_get(dev, "sclk_mipi");
> +		if (!IS_ERR(pll_clk))
> +			dsi->pll_clk_rate = clk_get_rate(pll_clk);
> +		else
> +			return PTR_ERR(pll_clk);
> +	}
>  
>  	ret = samsung_dsim_of_read_u32(node, "samsung,burst-clock-frequency",
> -				       &dsi->burst_clk_rate);
> +				       &dsi->burst_clk_rate, 0);
>  	if (ret < 0)
>  		return ret;
>  
>  	ret = samsung_dsim_of_read_u32(node, "samsung,esc-clock-frequency",
> -				       &dsi->esc_clk_rate);
> +				       &dsi->esc_clk_rate, 0);
>  	if (ret < 0)
>  		return ret;
>

On Wed, May 17, 2023 at 7:56 AM Lucas Stach <l.stach@pengutronix.de> wrote:
>
> Hi Adam,
>
> Am Montag, dem 15.05.2023 um 18:57 -0500 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.
> > Since it can be optional, change the message from an error to
> > dev_info.
> >
> > Signed-off-by: Adam Ford <aford173@gmail.com>
> > Tested-by: Chen-Yu Tsai <wenst@chromium.org>
> > Tested-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> > Reviewed-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> > ---
> >  drivers/gpu/drm/bridge/samsung-dsim.c | 23 ++++++++++++++++-------
> >  1 file changed, 16 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> > index bf4b33d2de76..08266303c261 100644
> > --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> > +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> > @@ -1712,11 +1712,11 @@ static const struct mipi_dsi_host_ops samsung_dsim_ops = {
> >  };
> >
> >  static int samsung_dsim_of_read_u32(const struct device_node *np,
> > -                                 const char *propname, u32 *out_value)
> > +                                 const char *propname, u32 *out_value, bool optional)
> >  {
> >       int ret = of_property_read_u32(np, propname, out_value);
> >
> > -     if (ret < 0)
> > +     if (ret < 0 && !optional)
> >               pr_err("%pOF: failed to get '%s' property\n", np, propname);
> >
> >       return ret;
> > @@ -1726,20 +1726,29 @@ static int samsung_dsim_parse_dt(struct samsung_dsim *dsi)
> >  {
> >       struct device *dev = dsi->dev;
> >       struct device_node *node = dev->of_node;
> > +     struct clk *pll_clk;
> >       int ret;
> >
> >       ret = samsung_dsim_of_read_u32(node, "samsung,pll-clock-frequency",
> > -                                    &dsi->pll_clk_rate);
> > -     if (ret < 0)
> > -             return ret;
> > +                                    &dsi->pll_clk_rate, 1);
> > +
> > +     /* If it doesn't exist, read it from the clock instead of failing */
> > +     if (ret < 0) {
> > +             dev_info(dev, "Using sclk_mipi for pll clock frequency\n");
>
> While this is certainly helpful while debugging the driver, I don't
> think it warrants a info print. Remove or downgrade to dev_dbg?

I can move to dbg.

>
> On the other hand the changed driver behavior should be documented in
> the devicetree binding by moving "samsung,pll-clock-frequency" into the
> optional properties and spelling out which clock rate is used when the
> property is absent.

Once this series is accepted, I was planning on doing a binding patch
which describes the items that are now optional followed by a patch to
add DSI->HDMI for the Beacon boards.  I can see the value in putting
the bindings patch in this series instead. I'll add it to the next
revision to cover both items that are now optional.

adam

>
> Regards,
> Lucas
>
> > +             pll_clk = devm_clk_get(dev, "sclk_mipi");
> > +             if (!IS_ERR(pll_clk))
> > +                     dsi->pll_clk_rate = clk_get_rate(pll_clk);
> > +             else
> > +                     return PTR_ERR(pll_clk);
> > +     }
> >
> >       ret = samsung_dsim_of_read_u32(node, "samsung,burst-clock-frequency",
> > -                                    &dsi->burst_clk_rate);
> > +                                    &dsi->burst_clk_rate, 0);
> >       if (ret < 0)
> >               return ret;
> >
> >       ret = samsung_dsim_of_read_u32(node, "samsung,esc-clock-frequency",
> > -                                    &dsi->esc_clk_rate);
> > +                                    &dsi->esc_clk_rate, 0);
> >       if (ret < 0)
> >               return ret;
> >
>