Recently, we round up new_hdisplay once at most, for bonded dsi, we
may need twice, since they are independent links, we should round up
each half separately. This also aligns with the hdisplay we program
later in dsi_timing_setup()

Example:
	full_hdisplay = 1904, dsc_bpp = 8, bpc = 8
	new_full_hdisplay = DIV_ROUND_UP(1904 * 8, 8 * 3) = 635

if we use half display
	new_half_hdisplay = DIV_ROUND_UP(952 * 8, 8 * 3) = 318
	new_full_display = 636

Fixes: 7c9e4a554d4a ("drm/msm/dsi: Reduce pclk rate for compression")
Signed-off-by: Pengyu Luo <mitltlatltl@gmail.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
---
v2: add a parameter desciption to the function doc (kernel test robot)
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 32 +++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index e8e83ee61e..06f094fc32 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -569,6 +569,7 @@ void dsi_link_clk_disable_v2(struct msm_dsi_host *msm_host)
  * dsi_adjust_pclk_for_compression() - Adjust the pclk rate for compression case
  * @mode: The selected mode for the DSI output
  * @dsc: DRM DSC configuration for this DSI output
+ * @is_bonded_dsi: True if two DSI controllers are bonded
  *
  * Adjust the pclk rate by calculating a new hdisplay proportional to
  * the compression ratio such that:
@@ -584,13 +585,30 @@ void dsi_link_clk_disable_v2(struct msm_dsi_host *msm_host)
  *  FIXME: Reconsider this if/when CMD mode handling is rewritten to use
  *  transfer time and data overhead as a starting point of the calculations.
  */
-static unsigned long dsi_adjust_pclk_for_compression(const struct drm_display_mode *mode,
-		const struct drm_dsc_config *dsc)
+static unsigned long
+dsi_adjust_pclk_for_compression(const struct drm_display_mode *mode,
+				const struct drm_dsc_config *dsc,
+				bool is_bonded_dsi)
 {
-	int new_hdisplay = DIV_ROUND_UP(mode->hdisplay * drm_dsc_get_bpp_int(dsc),
-			dsc->bits_per_component * 3);
+	int hdisplay, new_hdisplay, new_htotal;
 
-	int new_htotal = mode->htotal - mode->hdisplay + new_hdisplay;
+	/*
+	 * For bonded DSI, split hdisplay across two links and round up each
+	 * half separately, passing the full hdisplay would only round up once.
+	 * This also aligns with the hdisplay we program later in
+	 * dsi_timing_setup()
+	 */
+	hdisplay = mode->hdisplay;
+	if (is_bonded_dsi)
+		hdisplay /= 2;
+
+	new_hdisplay = DIV_ROUND_UP(hdisplay * drm_dsc_get_bpp_int(dsc),
+				    dsc->bits_per_component * 3);
+
+	if (is_bonded_dsi)
+		new_hdisplay *= 2;
+
+	new_htotal = mode->htotal - mode->hdisplay + new_hdisplay;
 
 	return mult_frac(mode->clock * 1000u, new_htotal, mode->htotal);
 }
@@ -603,12 +621,12 @@ static unsigned long dsi_get_pclk_rate(const struct drm_display_mode *mode,
 	pclk_rate = mode->clock * 1000u;
 
 	if (dsc)
-		pclk_rate = dsi_adjust_pclk_for_compression(mode, dsc);
+		pclk_rate = dsi_adjust_pclk_for_compression(mode, dsc, is_bonded_dsi);
 
 	/*
 	 * For bonded DSI mode, the current DRM mode has the complete width of the
 	 * panel. Since, the complete panel is driven by two DSI controllers,
-	 * the clock rates have to be split between the two dsi controllers.
+	 * the clock rates have to be split between the two DSI controllers.
 	 * Adjust the byte and pixel clock rates for each dsi host accordingly.
 	 */
 	if (is_bonded_dsi)
-- 
2.53.0

On Sun, Mar 08, 2026 at 03:06:27PM +0800, Pengyu Luo wrote:
> Recently, we round up new_hdisplay once at most, for bonded dsi, we
> may need twice, since they are independent links, we should round up
> each half separately. This also aligns with the hdisplay we program
> later in dsi_timing_setup()
> 
> Example:
> 	full_hdisplay = 1904, dsc_bpp = 8, bpc = 8
> 	new_full_hdisplay = DIV_ROUND_UP(1904 * 8, 8 * 3) = 635
> 
> if we use half display
> 	new_half_hdisplay = DIV_ROUND_UP(952 * 8, 8 * 3) = 318
> 	new_full_display = 636
> 
> Fixes: 7c9e4a554d4a ("drm/msm/dsi: Reduce pclk rate for compression")
> Signed-off-by: Pengyu Luo <mitltlatltl@gmail.com>
> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> ---
> v2: add a parameter desciption to the function doc (kernel test robot)
> ---
>  drivers/gpu/drm/msm/dsi/dsi_host.c | 32 +++++++++++++++++++++++-------
>  1 file changed, 25 insertions(+), 7 deletions(-)

The previous version has been picked up alrady (before the report came).
Would you mind sending a fix for it, describing the parameter?


-- 
With best wishes
Dmitry