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>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index e8e83ee61..db6da9937 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -584,13 +584,30 @@ 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);
 }
@@ -603,7 +620,7 @@ 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
-- 
2.53.0

Hi Pengyu,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on linus/master v7.0-rc2 next-20260306]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Pengyu-Luo/drm-msm-dsi-fix-pclk-rate-calculation-for-bonded-dsi/20260307-010943
base:   https://gitlab.freedesktop.org/drm/misc/kernel.git drm-misc-next
patch link:    https://lore.kernel.org/r/20260306163255.215456-1-mitltlatltl%40gmail.com
patch subject: [PATCH] drm/msm/dsi: fix pclk rate calculation for bonded dsi
config: arc-allyesconfig (https://download.01.org/0day-ci/archive/20260308/202603080314.XeqyRZ7A-lkp@intel.com/config)
compiler: arc-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260308/202603080314.XeqyRZ7A-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202603080314.XeqyRZ7A-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> Warning: drivers/gpu/drm/msm/dsi/dsi_host.c:590 function parameter 'is_bonded_dsi' not described in 'dsi_adjust_pclk_for_compression'
>> Warning: drivers/gpu/drm/msm/dsi/dsi_host.c:590 function parameter 'is_bonded_dsi' not described in 'dsi_adjust_pclk_for_compression'

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

On Sat, Mar 07, 2026 at 12:32:38AM +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>
> ---
>  drivers/gpu/drm/msm/dsi/dsi_host.c | 29 +++++++++++++++++++++++------
>  1 file changed, 23 insertions(+), 6 deletions(-)
> 

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>


-- 
With best wishes
Dmitry