[PATCH v2 1/2] drm/msm/dsi: improve/fix dsc pclk calculation

[PATCH v2 1/2] drm/msm/dsi: improve/fix dsc pclk calculation

[Jonathan Marek]

drm_mode_vrefresh() can introduce a large rounding error, avoid it.

Fixes: 7c9e4a554d4a ("drm/msm/dsi: Reduce pclk rate for compression")
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 185d7de0bf376..1205aa398e445 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -542,7 +542,7 @@ static unsigned long dsi_adjust_pclk_for_compression(const struct drm_display_mo
 
 	int new_htotal = mode->htotal - mode->hdisplay + new_hdisplay;
 
-	return new_htotal * mode->vtotal * drm_mode_vrefresh(mode);
+	return mult_frac(mode->clock * 1000u, new_htotal, mode->htotal);
 }
 
 static unsigned long dsi_get_pclk_rate(const struct drm_display_mode *mode,
-- 
2.45.1

[PATCH v2 2/2] drm/msm/dsi: fix 32-bit signed integer extension in pclk_rate calculation

[Jonathan Marek]

When (mode->clock * 1000) is larger than (1<<31), int to unsigned long
conversion will sign extend the int to 64 bits and the pclk_rate value
will be incorrect.

Fix this by making the result of the multiplication unsigned.

Note that above (1<<32) would still be broken and require more changes, but
its unlikely anyone will need that anytime soon.

Fixes: c4d8cfe516dc ("drm/msm/dsi: add implementation for helper functions")
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 1205aa398e445..a98d24b7cb00b 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -550,7 +550,7 @@ static unsigned long dsi_get_pclk_rate(const struct drm_display_mode *mode,
 {
 	unsigned long pclk_rate;
 
-	pclk_rate = mode->clock * 1000;
+	pclk_rate = mode->clock * 1000u;
 
 	if (dsc)
 		pclk_rate = dsi_adjust_pclk_for_compression(mode, dsc);
-- 
2.45.1

Re: [PATCH v2 1/2] drm/msm/dsi: improve/fix dsc pclk calculation

[Dmitry Baryshkov]

On Mon, Oct 07, 2024 at 01:01:48AM GMT, Jonathan Marek wrote:
> drm_mode_vrefresh() can introduce a large rounding error, avoid it.
> 
> Fixes: 7c9e4a554d4a ("drm/msm/dsi: Reduce pclk rate for compression")
> Signed-off-by: Jonathan Marek <jonathan@marek.ca>
> ---
>  drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

-- 
With best wishes
Dmitry

Re: [PATCH v2 2/2] drm/msm/dsi: fix 32-bit signed integer extension in pclk_rate calculation

[Dmitry Baryshkov]

On Mon, Oct 07, 2024 at 01:01:49AM GMT, Jonathan Marek wrote:
> When (mode->clock * 1000) is larger than (1<<31), int to unsigned long
> conversion will sign extend the int to 64 bits and the pclk_rate value
> will be incorrect.
> 
> Fix this by making the result of the multiplication unsigned.
> 
> Note that above (1<<32) would still be broken and require more changes, but
> its unlikely anyone will need that anytime soon.
> 
> Fixes: c4d8cfe516dc ("drm/msm/dsi: add implementation for helper functions")
> Signed-off-by: Jonathan Marek <jonathan@marek.ca>
> ---
>  drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

-- 
With best wishes
Dmitry

Re: [PATCH v2 2/2] drm/msm/dsi: fix 32-bit signed integer extension in pclk_rate calculation

[Abhinav Kumar]

On 10/6/2024 10:01 PM, Jonathan Marek wrote:
> When (mode->clock * 1000) is larger than (1<<31), int to unsigned long
> conversion will sign extend the int to 64 bits and the pclk_rate value
> will be incorrect.
> 
> Fix this by making the result of the multiplication unsigned.
> 
> Note that above (1<<32) would still be broken and require more changes, but
> its unlikely anyone will need that anytime soon.
> 
> Fixes: c4d8cfe516dc ("drm/msm/dsi: add implementation for helper functions")
> Signed-off-by: Jonathan Marek <jonathan@marek.ca>
> ---
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

Re: [PATCH v2 1/2] drm/msm/dsi: improve/fix dsc pclk calculation

[Abhinav Kumar]

On 10/6/2024 10:01 PM, Jonathan Marek wrote:
> drm_mode_vrefresh() can introduce a large rounding error, avoid it.
> 
> Fixes: 7c9e4a554d4a ("drm/msm/dsi: Reduce pclk rate for compression")
> Signed-off-by: Jonathan Marek <jonathan@marek.ca>
> ---
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>