[PATCH 0/2] drm/msm/dsi: support multiple DSC slices per packet

[PATCH 0/2] drm/msm/dsi: support multiple DSC slices per packet

[Alexander Koskovich]

This series adds support for sending multiple DSC slices in a single
DSI packet, which is required by some panels such as the JDI LPM026M648C.

The MSM DRM change was originally authored by Jonathan Marek [1], changed to
use an 'all slices in packet' flag which derives slice_per_pkt from slice_count
instead of manually specifying the number of slices per packet.

Was also split into two patches so they can go through different trees.

[1]: https://lore.kernel.org/all/20231114174218.19765-3-jonathan@marek.ca

Signed-off-by: Alexander Koskovich <akoskovich@pm.me>
---
Alexander Koskovich (2):
      drm/mipi-dsi: add flag for sending all DSC slices in one packet
      drm/msm/dsi: support DSC configurations with slice_per_pkt > 1

 drivers/gpu/drm/msm/dsi/dsi_host.c | 25 ++++++++++---------------
 include/drm/drm_mipi_dsi.h         |  2 ++
 2 files changed, 12 insertions(+), 15 deletions(-)
---
base-commit: f338e77383789c0cae23ca3d48adcc5e9e137e3c
change-id: 20260318-dsi-dsc-slice-per-pkt-f828429fbf0a

Best regards,
-- 
Alexander Koskovich <akoskovich@pm.me>

[PATCH 1/2] drm/mipi-dsi: add flag for sending all DSC slices in one packet

[Alexander Koskovich]

The MIPI DSI v1.3 spec defines two modes for transporting compressed
pixel data: one slice per packet or multiple slice widths in a single
packet (Section 8.8.24 Figure 40).

Add a MIPI_DSI_MODE_DSC_ALL_SLICES_IN_PKT flag that panel drivers can
set to indicate that all DSC slices for a line should be packed into a
single packet. When unset should default to 1 slice per packet.

Signed-off-by: Alexander Koskovich <akoskovich@pm.me>
---
 include/drm/drm_mipi_dsi.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 3aba7b380c8d..d3ad8c5d3ebe 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -138,6 +138,8 @@ struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node);
 #define MIPI_DSI_MODE_LPM		BIT(11)
 /* transmit data ending at the same time for all lanes within one hsync */
 #define MIPI_DSI_HS_PKT_END_ALIGNED	BIT(12)
+/* pack all DSC slices for a line into a single packet */
+#define MIPI_DSI_MODE_DSC_ALL_SLICES_IN_PKT	BIT(13)
 
 enum mipi_dsi_pixel_format {
 	MIPI_DSI_FMT_RGB888,

-- 
2.53.0

Re: [PATCH 1/2] drm/mipi-dsi: add flag for sending all DSC slices in one packet

[Dmitry Baryshkov]

On Wed, Mar 18, 2026 at 07:32:58AM +0000, Alexander Koskovich wrote:
> The MIPI DSI v1.3 spec defines two modes for transporting compressed
> pixel data: one slice per packet or multiple slice widths in a single
> packet (Section 8.8.24 Figure 40).
> 
> Add a MIPI_DSI_MODE_DSC_ALL_SLICES_IN_PKT flag that panel drivers can
> set to indicate that all DSC slices for a line should be packed into a
> single packet. When unset should default to 1 slice per packet.
> 
> Signed-off-by: Alexander Koskovich <akoskovich@pm.me>
> ---
>  include/drm/drm_mipi_dsi.h | 2 ++
>  1 file changed, 2 insertions(+)
> 

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

However I'd also like to hear an optinion from somebody else with the
higher authority.

-- 
With best wishes
Dmitry

[PATCH 2/2] drm/msm/dsi: support DSC configurations with slice_per_pkt > 1

[Alexander Koskovich]

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

Re: [PATCH 2/2] drm/msm/dsi: support DSC configurations with slice_per_pkt > 1

[Dmitry Baryshkov]

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

Re: [PATCH 2/2] drm/msm/dsi: support DSC configurations with slice_per_pkt > 1

[Neil Armstrong]

On 3/18/26 10:39, Dmitry Baryshkov wrote:
> 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.

Please retain `Signed-off-by: Jonathan Marek <jonathan@marek.ca>` since the only
major difference with the original patch is moving the drm_mipi_dsi.h change to
another patch.

> 
> 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(-)
>>
> 

Re: [PATCH 2/2] drm/msm/dsi: support DSC configurations with slice_per_pkt > 1

[Alexander Koskovich]

On Thursday, May 21st, 2026 at 3:50 AM, Neil Armstrong <neil.armstrong@linaro.org> wrote:

> On 3/18/26 10:39, Dmitry Baryshkov wrote:
> > 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.
> 
> Please retain `Signed-off-by: Jonathan Marek <jonathan@marek.ca>` since the only
> major difference with the original patch is moving the drm_mipi_dsi.h change to
> another patch.

Yeah, made sure to add his Signed-off-by to v2:
https://lore.kernel.org/linux-arm-msm/20260318-dsi-dsc-slice-per-pkt-v2-2-0a1b316f8250@pm.me

> 
> >
> > 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(-)
> >>
> >
> 
> 
>

Re: [PATCH 0/2] drm/msm/dsi: support multiple DSC slices per packet

[Maxime Ripard]

On Wed, 18 Mar 2026 07:32:53 +0000, Alexander Koskovich wrote:
> This series adds support for sending multiple DSC slices in a single
> DSI packet, which is required by some panels such as the JDI LPM026M648C.
> 
> The MSM DRM change was originally authored by Jonathan Marek [1], changed to
> use an 'all slices in packet' flag which derives slice_per_pkt from slice_count
> 
> [ ... ]

Acked-by: Maxime Ripard <mripard@kernel.org>

Thanks!
Maxime