diff mbox series

[09/27] drm/rockchip: dw_hdmi: Set cur_ctr to 0 always

Message ID 20220126145549.617165-10-s.hauer@pengutronix.de (mailing list archive)
State New
Headers show
Series drm/rockchip: RK356x VOP2 support | expand

Commit Message

Sascha Hauer Jan. 26, 2022, 2:55 p.m. UTC
From: Douglas Anderson <dianders@chromium.org>

Jitter was improved by lowering the MPLL bandwidth to account for high
frequency noise in the rk3288 PLL.  In each case MPLL bandwidth was
lowered only enough to get us a comfortable margin.  We believe that
lowering the bandwidth like this is safe given sufficient testing.

Changes since v3:
- new patch

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Yakir Yang <ykk@rock-chips.com>
(am from https://patchwork.kernel.org/patch/9223301/)
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c | 16 ++--------------
 1 file changed, 2 insertions(+), 14 deletions(-)

Comments

Doug Anderson Jan. 26, 2022, 3:42 p.m. UTC | #1
Hi,

On Wed, Jan 26, 2022 at 6:58 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:
>
> From: Douglas Anderson <dianders@chromium.org>
>
> Jitter was improved by lowering the MPLL bandwidth to account for high
> frequency noise in the rk3288 PLL.  In each case MPLL bandwidth was
> lowered only enough to get us a comfortable margin.  We believe that
> lowering the bandwidth like this is safe given sufficient testing.
>
> Changes since v3:
> - new patch
>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> Signed-off-by: Yakir Yang <ykk@rock-chips.com>
> (am from https://patchwork.kernel.org/patch/9223301/)

Probably remove the "am from" line? It's not standard in upstream and
that link doesn't seem to go anywhere anymore...


> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c | 16 ++--------------
>  1 file changed, 2 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
> index c44eb4d2e2d5..77f82a4fd027 100644
> --- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
> +++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
> @@ -176,20 +176,8 @@ static const struct dw_hdmi_mpll_config rockchip_mpll_cfg[] = {
>  static const struct dw_hdmi_curr_ctrl rockchip_cur_ctr[] = {
>         /*      pixelclk    bpp8    bpp10   bpp12 */
>         {
> -               40000000,  { 0x0018, 0x0018, 0x0018 },
> -       }, {
> -               65000000,  { 0x0028, 0x0028, 0x0028 },
> -       }, {
> -               66000000,  { 0x0038, 0x0038, 0x0038 },
> -       }, {
> -               74250000,  { 0x0028, 0x0038, 0x0038 },
> -       }, {
> -               83500000,  { 0x0028, 0x0038, 0x0038 },
> -       }, {
> -               146250000, { 0x0038, 0x0038, 0x0038 },
> -       }, {
> -               148500000, { 0x0000, 0x0038, 0x0038 },
> -       }, {
> +               600000000, { 0x0000, 0x0000, 0x0000 },
> +       },  {

This is what we did for rk3288. I can't personally vouch for the
effects on other SoCs.

-Doug
Sascha Hauer Jan. 27, 2022, 11:06 a.m. UTC | #2
On Wed, Jan 26, 2022 at 07:42:48AM -0800, Doug Anderson wrote:
> Hi,
> 
> On Wed, Jan 26, 2022 at 6:58 AM Sascha Hauer <s.hauer@pengutronix.de> wrote:
> >
> > From: Douglas Anderson <dianders@chromium.org>
> >
> > Jitter was improved by lowering the MPLL bandwidth to account for high
> > frequency noise in the rk3288 PLL.  In each case MPLL bandwidth was
> > lowered only enough to get us a comfortable margin.  We believe that
> > lowering the bandwidth like this is safe given sufficient testing.
> >
> > Changes since v3:
> > - new patch
> >
> > Signed-off-by: Douglas Anderson <dianders@chromium.org>
> > Signed-off-by: Yakir Yang <ykk@rock-chips.com>
> > (am from https://patchwork.kernel.org/patch/9223301/)
> 
> Probably remove the "am from" line? It's not standard in upstream and
> that link doesn't seem to go anywhere anymore...
> 
> 
> > Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> > ---
> >  drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c | 16 ++--------------
> >  1 file changed, 2 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
> > index c44eb4d2e2d5..77f82a4fd027 100644
> > --- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
> > +++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
> > @@ -176,20 +176,8 @@ static const struct dw_hdmi_mpll_config rockchip_mpll_cfg[] = {
> >  static const struct dw_hdmi_curr_ctrl rockchip_cur_ctr[] = {
> >         /*      pixelclk    bpp8    bpp10   bpp12 */
> >         {
> > -               40000000,  { 0x0018, 0x0018, 0x0018 },
> > -       }, {
> > -               65000000,  { 0x0028, 0x0028, 0x0028 },
> > -       }, {
> > -               66000000,  { 0x0038, 0x0038, 0x0038 },
> > -       }, {
> > -               74250000,  { 0x0028, 0x0038, 0x0038 },
> > -       }, {
> > -               83500000,  { 0x0028, 0x0038, 0x0038 },
> > -       }, {
> > -               146250000, { 0x0038, 0x0038, 0x0038 },
> > -       }, {
> > -               148500000, { 0x0000, 0x0038, 0x0038 },
> > -       }, {
> > +               600000000, { 0x0000, 0x0000, 0x0000 },
> > +       },  {
> 
> This is what we did for rk3288. I can't personally vouch for the
> effects on other SoCs.

Fair enough. Rockchip has this patch in their downstream Kernel, so I am
confident it works on SoCs newer as the rk3288 as well. I don't know how
much they care about the older SoCs, but it seems there is only the
rk3228 that is older than the rk3288 that is supported by this driver.

Sascha
diff mbox series

Patch

diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
index c44eb4d2e2d5..77f82a4fd027 100644
--- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
@@ -176,20 +176,8 @@  static const struct dw_hdmi_mpll_config rockchip_mpll_cfg[] = {
 static const struct dw_hdmi_curr_ctrl rockchip_cur_ctr[] = {
 	/*      pixelclk    bpp8    bpp10   bpp12 */
 	{
-		40000000,  { 0x0018, 0x0018, 0x0018 },
-	}, {
-		65000000,  { 0x0028, 0x0028, 0x0028 },
-	}, {
-		66000000,  { 0x0038, 0x0038, 0x0038 },
-	}, {
-		74250000,  { 0x0028, 0x0038, 0x0038 },
-	}, {
-		83500000,  { 0x0028, 0x0038, 0x0038 },
-	}, {
-		146250000, { 0x0038, 0x0038, 0x0038 },
-	}, {
-		148500000, { 0x0000, 0x0038, 0x0038 },
-	}, {
+		600000000, { 0x0000, 0x0000, 0x0000 },
+	},  {
 		~0UL,      { 0x0000, 0x0000, 0x0000},
 	}
 };