linux-kernel - [PATCH v3 1/3] drm/msm/dsi: support DSC configurations with slice_per

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Message-Id: <20250924-dsi-dual-panel-upstream-v3-1-6927284f1098@linaro.org>
Date: Wed, 24 Sep 2025 23:08:10 +0800
From: Jun Nie <jun.nie@...aro.org>
To: Rob Clark <robin.clark@....qualcomm.com>, 
 Abhinav Kumar <abhinav.kumar@...ux.dev>, 
 Jessica Zhang <jessica.zhang@....qualcomm.com>, 
 Dmitry Baryshkov <lumag@...nel.org>, Sean Paul <sean@...rly.run>, 
 Marijn Suijten <marijn.suijten@...ainline.org>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, 
 Krishna Manikandan <quic_mkrishn@...cinc.com>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 devicetree@...r.kernel.org, Jun Nie <jun.nie@...aro.org>, 
 Jonathan Marek <jonathan@...ek.ca>
Subject: [PATCH v3 1/3] drm/msm/dsi: support DSC configurations with
 slice_per_pkt > 1

Some panels support multiple slice to be sent in a single DSC packet. And
this feature is a must for specific panels, such as JDI LPM026M648C. Add a
dsc_slice_per_pkt member into struct mipi_dsi_device and support the
feature in msm mdss driver.

Co-developed-by: Jonathan Marek <jonathan@...ek.ca>
Signed-off-by: Jonathan Marek <jonathan@...ek.ca>
Signed-off-by: Jun Nie <jun.nie@...aro.org>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 25 ++++++++++---------------
 include/drm/drm_mipi_dsi.h         |  2 ++
 2 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index f297e3de8c3dc4e1326e70c78c046b5a19568cef..de51cb02f267205320c5a94fc4188413e05907e6 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -157,6 +157,7 @@ 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;
@@ -849,17 +850,10 @@ 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);
@@ -1008,12 +1002,8 @@ 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) |
@@ -1623,8 +1613,13 @@ 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;
+		msm_host->dsc_slice_per_pkt = dsi->dsc_slice_per_pkt;
+		/* for backwards compatibility, assume 1 if not set */
+		if (!msm_host->dsc_slice_per_pkt)
+			msm_host->dsc_slice_per_pkt = 1;
+	}
 
 	ret = dsi_dev_attach(msm_host->pdev);
 	if (ret)
diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 6d2c08e8110151a97620389197f1ef79c058329d..5a85ba01f402a3866b70828391bb417bb8dd5956 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -182,6 +182,7 @@ struct mipi_dsi_device_info {
  * be set to the real limits of the hardware, zero is only accepted for
  * legacy drivers
  * @dsc: panel/bridge DSC pps payload to be sent
+ * @dsc_slice_per_pkt: number of DSC slices to be sent as in a single packet
  */
 struct mipi_dsi_device {
 	struct mipi_dsi_host *host;
@@ -196,6 +197,7 @@ struct mipi_dsi_device {
 	unsigned long hs_rate;
 	unsigned long lp_rate;
 	struct drm_dsc_config *dsc;
+	unsigned int dsc_slice_per_pkt;
 };
 
 /**

-- 
2.34.1