Some panels support multiple slice to be sent in a single DSC packet and
this feature is a must for specific panels, such as the JDI LPM026M648C.

Use the MIPI_DSI_MODE_DSC_ALL_SLICES_IN_PKT flag to derive slice_per_pkt
from slice_count, note that most panels are expected to just work with
just one slice per packet.

This change was originally authored by Jonathan Marek:
https://lore.kernel.org/all/20231114174218.19765-3-jonathan@marek.ca

Signed-off-by: Alexander Koskovich <akoskovich@pm.me>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 25 ++++++++++---------------
 1 file changed, 10 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index db6da99375a1..758b076ee4bf 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -166,6 +166,7 @@ struct msm_dsi_host {
 
 	struct drm_display_mode *mode;
 	struct drm_dsc_config *dsc;
+	unsigned int dsc_slice_per_pkt;
 
 	/* connected device info */
 	unsigned int channel;
@@ -927,17 +928,10 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
 	slice_per_intf = dsc->slice_count;
 
 	total_bytes_per_intf = dsc->slice_chunk_size * slice_per_intf;
-	bytes_per_pkt = dsc->slice_chunk_size; /* * slice_per_pkt; */
+	bytes_per_pkt = dsc->slice_chunk_size * msm_host->dsc_slice_per_pkt;
 
 	eol_byte_num = total_bytes_per_intf % 3;
-
-	/*
-	 * Typically, pkt_per_line = slice_per_intf * slice_per_pkt.
-	 *
-	 * Since the current driver only supports slice_per_pkt = 1,
-	 * pkt_per_line will be equal to slice per intf for now.
-	 */
-	pkt_per_line = slice_per_intf;
+	pkt_per_line = slice_per_intf / msm_host->dsc_slice_per_pkt;
 
 	if (is_cmd_mode) /* packet data type */
 		reg = DSI_COMMAND_COMPRESSION_MODE_CTRL_STREAM0_DATATYPE(MIPI_DSI_DCS_LONG_WRITE);
@@ -1088,12 +1082,8 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
 		else
 			/*
 			 * When DSC is enabled, WC = slice_chunk_size * slice_per_pkt + 1.
-			 * Currently, the driver only supports default value of slice_per_pkt = 1
-			 *
-			 * TODO: Expand mipi_dsi_device struct to hold slice_per_pkt info
-			 *       and adjust DSC math to account for slice_per_pkt.
 			 */
-			wc = msm_host->dsc->slice_chunk_size + 1;
+			wc = msm_host->dsc->slice_chunk_size * msm_host->dsc_slice_per_pkt + 1;
 
 		dsi_write(msm_host, REG_DSI_CMD_MDP_STREAM0_CTRL,
 			DSI_CMD_MDP_STREAM0_CTRL_WORD_COUNT(wc) |
@@ -1702,8 +1692,13 @@ static int dsi_host_attach(struct mipi_dsi_host *host,
 	msm_host->lanes = dsi->lanes;
 	msm_host->format = dsi->format;
 	msm_host->mode_flags = dsi->mode_flags;
-	if (dsi->dsc)
+	if (dsi->dsc) {
 		msm_host->dsc = dsi->dsc;
+		if (dsi->mode_flags & MIPI_DSI_MODE_DSC_ALL_SLICES_IN_PKT)
+			msm_host->dsc_slice_per_pkt = dsi->dsc->slice_count;
+		else
+			msm_host->dsc_slice_per_pkt = 1;
+	}
 
 	ret = dsi_dev_attach(msm_host->pdev);
 	if (ret)

-- 
2.53.0

On Wed, Mar 18, 2026 at 07:33:03AM +0000, Alexander Koskovich wrote:
> Some panels support multiple slice to be sent in a single DSC packet and
> this feature is a must for specific panels, such as the JDI LPM026M648C.
> 
> Use the MIPI_DSI_MODE_DSC_ALL_SLICES_IN_PKT flag to derive slice_per_pkt
> from slice_count, note that most panels are expected to just work with
> just one slice per packet.
> 
> This change was originally authored by Jonathan Marek:
> https://lore.kernel.org/all/20231114174218.19765-3-jonathan@marek.ca

This is a wrong way to give attribution. Either please retain the author
and Jonathan's SoB or use Co-developed-by and still Jonathan's SoB.

The patch looks good to me.

> 
> Signed-off-by: Alexander Koskovich <akoskovich@pm.me>
> ---
>  drivers/gpu/drm/msm/dsi/dsi_host.c | 25 ++++++++++---------------
>  1 file changed, 10 insertions(+), 15 deletions(-)
> 

-- 
With best wishes
Dmitry