[v4,63/78] drm/vc4: hdmi: Use clk_set_min_rate instead
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Message ID a47487bc8873abe33499e79d3c10d085e341614e.1594230107.git-series.maxime@cerno.tech
State New
Headers show
Series
  • drm/vc4: Support BCM2711 Display Pipeline
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Commit Message

Maxime Ripard July 8, 2020, 5:42 p.m. UTC
The HSM clock needs to be running at 101% the pixel clock of the HDMI
controller, however it's shared between the two HDMI controllers, which
means that if the resolutions are different between the two HDMI
controllers, and the lowest resolution is on the second (in enable order)
controller, the first HDMI controller will end up with a smaller than
expected clock rate.

Since we don't really need an exact frequency there, we can simply change
the minimum rate we expect instead.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Dave Stevenson July 28, 2020, 2:57 p.m. UTC | #1
Hi Maxime

On Wed, 8 Jul 2020 at 18:44, Maxime Ripard <maxime@cerno.tech> wrote:
>
> The HSM clock needs to be running at 101% the pixel clock of the HDMI
> controller, however it's shared between the two HDMI controllers, which
> means that if the resolutions are different between the two HDMI
> controllers, and the lowest resolution is on the second (in enable order)
> controller, the first HDMI controller will end up with a smaller than
> expected clock rate.
>
> Since we don't really need an exact frequency there, we can simply change
> the minimum rate we expect instead.
>
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>

Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 9f30fab744f2..d99188c90ff9 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -462,7 +462,7 @@ static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
>          * pixel clock, but HSM ends up being the limiting factor.
>          */
>         hsm_rate = max_t(unsigned long, 120000000, (pixel_rate / 100) * 101);
> -       ret = clk_set_rate(vc4_hdmi->hsm_clock, hsm_rate);
> +       ret = clk_set_min_rate(vc4_hdmi->hsm_clock, hsm_rate);
>         if (ret) {
>                 DRM_ERROR("Failed to set HSM clock rate: %d\n", ret);
>                 return;
> --
> git-series 0.9.1

Patch
diff mbox series

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 9f30fab744f2..d99188c90ff9 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -462,7 +462,7 @@  static void vc4_hdmi_encoder_enable(struct drm_encoder *encoder)
 	 * pixel clock, but HSM ends up being the limiting factor.
 	 */
 	hsm_rate = max_t(unsigned long, 120000000, (pixel_rate / 100) * 101);
-	ret = clk_set_rate(vc4_hdmi->hsm_clock, hsm_rate);
+	ret = clk_set_min_rate(vc4_hdmi->hsm_clock, hsm_rate);
 	if (ret) {
 		DRM_ERROR("Failed to set HSM clock rate: %d\n", ret);
 		return;