[PATCH v3 0/6] Introduce MSM-specific DSC helpers

[PATCH v3 0/6] Introduce MSM-specific DSC helpers

[Jessica Zhang]

There are some overlap in calculations for MSM-specific DSC variables between DP and DSI. In addition, the calculations for initial_scale_value and det_thresh_flatness that are defined within the DSC 1.2 specifications, but aren't yet included in drm_dsc_helper.c.

This series moves these calculations to a shared msm_dsc_helper.c file and defines drm_dsc_helper methods for initial_scale_value and det_thresh_flatness.

Note: For now, the MSM specific helper methods are only called for the DSI path, but will called for DP once DSC 1.2 support for DP has been added.

Depends on: "drm/i915: move DSC RC tables to drm_dsc_helper.c" [1]

[1] https://patchwork.freedesktop.org/series/114472/

---
Changes in v3:
- Cleaned up unused parameters
- Reworded some calculations for clarity
- Changed get_bytes_per_soft_slice() to a public method
- Added comment documentation to MSM DSC helpers
- Changed msm_dsc_get_eol_byte_num() to *_get_bytes_per_intf()
- Split dsi_timing_setup() hdisplay calculation to a separate patch
- Dropped 78c8b81d57d8 ("drm/display/dsc: Add flatness and initial scale
  value calculations") patch as it was absorbed in Dmitry's DSC series [1]
- Link to v2: https://lore.kernel.org/r/20230329-rfc-msm-dsc-helper-v2-0-3c13ced536b2@quicinc.com

Changes in v2:
- Changed det_thresh_flatness to flatness_det_thresh
- Moved msm_dsc_helper files to msm/ directory
- Fixed type mismatch issues in MSM DSC helpers
- Dropped MSM_DSC_SLICE_PER_PKT macro
- Removed get_comp_ratio() helper
- Style changes to improve readability
- Use drm_dsc_get_bpp_int() instead of DSC_BPP macro
- Picked up Fixes tags for patches 3/5 and 4/5
- Picked up Reviewed-by for patch 4/5
- Split eol_byte_num and pkt_per_line calculation into a separate patch
- Moved pclk_per_line calculation into `if (dsc)` block in
  dsi_timing_setup()
- Link to v1: https://lore.kernel.org/r/20230329-rfc-msm-dsc-helper-v1-0-f3e479f59b6d@quicinc.com

---
Jessica Zhang (6):
      drm/msm: Add MSM-specific DSC helper methods
      drm/msm/dpu: Use DRM DSC helper for det_thresh_flatness
      drm/msm/dpu: Fix slice_last_group_size calculation
      drm/msm/dsi: Use MSM and DRM DSC helper methods
      drm/msm/dsi: update hdisplay calculation for dsi_timing_setup
      drm/msm/dsi: Fix calculations pkt_per_line

 drivers/gpu/drm/msm/Makefile               |  1 +
 drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c |  9 ++--
 drivers/gpu/drm/msm/dsi/dsi_host.c         | 22 ++++++++--
 drivers/gpu/drm/msm/msm_dsc_helper.c       | 47 ++++++++++++++++++++
 drivers/gpu/drm/msm/msm_dsc_helper.h       | 70 ++++++++++++++++++++++++++++++
 5 files changed, 142 insertions(+), 7 deletions(-)
---
base-commit: 56777fc93a145afcf71b92ba4281250f59ba6d9b
change-id: 20230329-rfc-msm-dsc-helper-981a95edfbd0

Best regards,
-- 
Jessica Zhang <quic_jesszhan@quicinc.com>

[PATCH v3 1/6] drm/msm: Add MSM-specific DSC helper methods

[Jessica Zhang]

Introduce MSM-specific DSC helper methods, as some calculations are
common between DP and DSC.

Changes in v2:
- Moved files up to msm/ directory
- Dropped get_comp_ratio() helper
- Used drm_int2fixp() to convert to integers to fp
- Style changes to improve readability
- Dropped unused bpp variable in msm_dsc_get_dce_bytes_per_line()
- Changed msm_dsc_get_slice_per_intf() to a static inline method
- Dropped last division step of msm_dsc_get_pclk_per_line() and changed
  method name accordingly
- Changed DSC_BPP macro to drm_dsc_get_bpp_int() helper method
- Fixed some math issues caused by passing in incorrect types to
  drm_fixed methods in get_bytes_per_soft_slice()

Changes in v3:
- Dropped src_bpp parameter from all methods -- src_bpp can be
  calculated as dsc->bits_per_component * 3
- Dropped intf_width parameter from get_bytes_per_soft_slice()
- Moved dsc->bits_per_component to numerator calculation in
  get_bytes_per_soft_slice()
- Renamed msm_dsc_get_uncompressed_pclk_per_line to
  *_get_uncompressed_pclk_per_intf()
- Removed dsc->slice_width check from
  msm_dsc_get_uncompressed_pclk_per_intf()
- Made get_bytes_per_soft_slice() a public method (this will be called
  later to help calculate DP pclk params)
- Added documentation in comments
- Moved extra_eol_bytes math out of msm_dsc_get_eol_byte_num() and
  renamed msm_dsc_get_eol_byte_num to *_get_bytes_per_intf.

Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
---
 drivers/gpu/drm/msm/Makefile         |  1 +
 drivers/gpu/drm/msm/msm_dsc_helper.c | 47 ++++++++++++++++++++++++
 drivers/gpu/drm/msm/msm_dsc_helper.h | 70 ++++++++++++++++++++++++++++++++++++
 3 files changed, 118 insertions(+)

diff --git a/drivers/gpu/drm/msm/Makefile b/drivers/gpu/drm/msm/Makefile
index 7274c41228ed..b814fc80e2d5 100644
--- a/drivers/gpu/drm/msm/Makefile
+++ b/drivers/gpu/drm/msm/Makefile
@@ -94,6 +94,7 @@ msm-y += \
 	msm_atomic_tracepoints.o \
 	msm_debugfs.o \
 	msm_drv.o \
+	msm_dsc_helper.o \
 	msm_fb.o \
 	msm_fence.o \
 	msm_gem.o \
diff --git a/drivers/gpu/drm/msm/msm_dsc_helper.c b/drivers/gpu/drm/msm/msm_dsc_helper.c
new file mode 100644
index 000000000000..c8c530211f50
--- /dev/null
+++ b/drivers/gpu/drm/msm/msm_dsc_helper.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <drm/drm_fixed.h>
+
+#include "msm_drv.h"
+#include "msm_dsc_helper.h"
+
+s64 get_bytes_per_soft_slice(struct drm_dsc_config *dsc)
+{
+	int bpp = msm_dsc_get_bpp_int(dsc);
+	s64 numerator_fp, denominator_fp;
+	s64 comp_ratio_fp = drm_fixp_from_fraction(dsc->bits_per_component * 3, bpp);
+
+	numerator_fp = drm_int2fixp(dsc->slice_width * 3 * dsc->bits_per_component);
+	denominator_fp = drm_fixp_mul(comp_ratio_fp, drm_int2fixp(8));
+
+	return drm_fixp_div(numerator_fp, denominator_fp);
+}
+
+u32 msm_dsc_get_bytes_per_intf(struct drm_dsc_config *dsc, int intf_width)
+{
+	u32 bytes_per_soft_slice, bytes_per_intf;
+	s64 bytes_per_soft_slice_fp;
+	int slice_per_intf = msm_dsc_get_slice_per_intf(dsc, intf_width);
+
+	bytes_per_soft_slice_fp = get_bytes_per_soft_slice(dsc);
+	bytes_per_soft_slice = drm_fixp2int_ceil(bytes_per_soft_slice_fp);
+
+	bytes_per_intf = bytes_per_soft_slice * slice_per_intf;
+
+	return bytes_per_intf;
+}
+
+int msm_dsc_get_uncompressed_pclk_per_intf(struct drm_dsc_config *dsc)
+{
+	s64 data_width;
+
+	data_width = drm_fixp_mul(drm_int2fixp(dsc->slice_count),
+			get_bytes_per_soft_slice(dsc));
+
+	return drm_fixp2int_ceil(data_width);
+}
diff --git a/drivers/gpu/drm/msm/msm_dsc_helper.h b/drivers/gpu/drm/msm/msm_dsc_helper.h
new file mode 100644
index 000000000000..5ee972eb247c
--- /dev/null
+++ b/drivers/gpu/drm/msm/msm_dsc_helper.h
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved
+ */
+
+#ifndef MSM_DSC_HELPER_H_
+#define MSM_DSC_HELPER_H_
+
+#include <drm/display/drm_dsc_helper.h>
+#include <drm/drm_modes.h>
+
+/*
+ * Helper methods for MSM specific DSC calculations that are common between timing engine,
+ * DSI, and DP.
+ */
+
+/**
+ * msm_dsc_get_bpp_int - get bits per pixel integer value
+ * @dsc: Pointer to drm dsc config struct
+ */
+static inline int msm_dsc_get_bpp_int(struct drm_dsc_config *dsc)
+{
+	WARN_ON_ONCE(dsc->bits_per_pixel & 0xf);
+	return dsc->bits_per_pixel >> 4;
+}
+
+/**
+ * msm_dsc_get_slice_per_intf - get number of slices per interface
+ * @dsc: Pointer to drm dsc config struct
+ * @intf_width: interface width
+ */
+static inline int msm_dsc_get_slice_per_intf(struct drm_dsc_config *dsc, int intf_width)
+{
+	return DIV_ROUND_UP(intf_width, dsc->slice_width);
+}
+
+/**
+ * msm_dsc_get_dce_bytes_per_line - get bytes per line to help calculate data width
+ *	when configuring the timing engine
+ * @dsc: Pointer to drm dsc config struct
+ * @intf_width: interface width
+ */
+static inline u32 msm_dsc_get_dce_bytes_per_line(struct drm_dsc_config *dsc, int intf_width)
+{
+	return DIV_ROUND_UP(msm_dsc_get_bpp_int(dsc) * intf_width, 8);
+}
+
+/**
+ * get_bytes_per_soft_slice - get size of each soft slice for dsc
+ * @dsc: Pointer to drm dsc config struct
+ */
+s64 get_bytes_per_soft_slice(struct drm_dsc_config *dsc);
+
+/**
+ * msm_dsc_get_bytes_per_intf - get total bytes per interface
+ * @dsc: Pointer to drm dsc config struct
+ * @intf_width: interface width
+ */
+u32 msm_dsc_get_bytes_per_intf(struct drm_dsc_config *dsc, int intf_width);
+
+/**
+ * msm_dsc_get_uncompressed_pclk_per_intf - Calculate uncompressed pclk per line.
+ * @dsc: Pointer to drm dsc config struct
+ *
+ * Note: This value will then be passed along to DSI and DP to calculate pclk_per_intf.
+ * This is because DSI and DP divide the uncompressed pclk_per_intf by different
+ * values depending on if widebus is enabled.
+ */
+int msm_dsc_get_uncompressed_pclk_per_intf(struct drm_dsc_config *dsc);
+#endif /* MSM_DSC_HELPER_H_ */

-- 
2.40.0

[PATCH v3 2/6] drm/msm/dpu: Use DRM DSC helper for det_thresh_flatness

[Jessica Zhang]

Use the DRM DSC helper for det_thresh_flatness to match downstream
implementation and the DSC spec.

Changes in V2:
- Added a Fixes tag

Fixes: c110cfd1753e ("drm/msm/disp/dpu1: Add support for DSC")
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
index 619926da1441..b952f7d2b7f5 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
@@ -3,6 +3,8 @@
  * Copyright (c) 2020-2022, Linaro Limited
  */
 
+#include <drm/display/drm_dsc_helper.h>
+
 #include "dpu_kms.h"
 #include "dpu_hw_catalog.h"
 #include "dpu_hwio.h"
@@ -102,7 +104,7 @@ static void dpu_hw_dsc_config(struct dpu_hw_dsc *hw_dsc,
 	data |= dsc->final_offset;
 	DPU_REG_WRITE(c, DSC_DSC_OFFSET, data);
 
-	det_thresh_flatness = 7 + 2 * (dsc->bits_per_component - 8);
+	det_thresh_flatness = drm_dsc_calculate_flatness_det_thresh(dsc);
 	data = det_thresh_flatness << 10;
 	data |= dsc->flatness_max_qp << 5;
 	data |= dsc->flatness_min_qp;

-- 
2.40.0

[PATCH v3 3/6] drm/msm/dpu: Fix slice_last_group_size calculation

[Jessica Zhang]

Correct the math for slice_last_group_size so that it matches the
calculations downstream.

Changes in v3:
- Reworded slice_last_group_size calculation to
  `(dsc->slice_width + 2) % 3`

Fixes: c110cfd1753e ("drm/msm/disp/dpu1: Add support for DSC")
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
index b952f7d2b7f5..ff1c8f92fb20 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_dsc.c
@@ -56,9 +56,10 @@ static void dpu_hw_dsc_config(struct dpu_hw_dsc *hw_dsc,
 	if (is_cmd_mode)
 		initial_lines += 1;
 
-	slice_last_group_size = 3 - (dsc->slice_width % 3);
+	slice_last_group_size = (dsc->slice_width + 2) % 3;
+
 	data = (initial_lines << 20);
-	data |= ((slice_last_group_size - 1) << 18);
+	data |= (slice_last_group_size << 18);
 	/* bpp is 6.4 format, 4 LSBs bits are for fractional part */
 	data |= (dsc->bits_per_pixel << 8);
 	data |= (dsc->block_pred_enable << 7);

-- 
2.40.0

[PATCH v3 4/6] drm/msm/dsi: Use MSM and DRM DSC helper methods

[Jessica Zhang]

Use MSM and DRM DSC helper methods to configure DSC for DSI.

Changes in V2:
- *_calculate_initial_scale_value --> *_set_initial_scale_value
- Split pkt_per_line and eol_byte_num changes to a separate patch
- Moved pclk_per_line calculation to hdisplay adjustment in `if (dsc)`
  block of dsi_update_dsc_timing()

Changes in v3:
- Split pclk_per_intf calculation into a separate patch
- Added slice_width check to dsi_timing_setup
- Used MSM DSC helper to calculate total_bytes_per_intf

Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 74d38f90398a..6a6218a9655f 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -28,6 +28,7 @@
 #include "dsi.xml.h"
 #include "sfpb.xml.h"
 #include "dsi_cfg.h"
+#include "msm_dsc_helper.h"
 #include "msm_kms.h"
 #include "msm_gem.h"
 #include "phy/dsi_phy.h"
@@ -848,7 +849,7 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
 	/* first calculate dsc parameters and then program
 	 * compress mode registers
 	 */
-	slice_per_intf = DIV_ROUND_UP(hdisplay, dsc->slice_width);
+	slice_per_intf = msm_dsc_get_slice_per_intf(dsc, hdisplay);
 
 	/*
 	 * If slice_count is greater than slice_per_intf
@@ -858,7 +859,7 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
 	if (dsc->slice_count > slice_per_intf)
 		dsc->slice_count = 1;
 
-	total_bytes_per_intf = dsc->slice_chunk_size * slice_per_intf;
+	total_bytes_per_intf = msm_dsc_get_bytes_per_intf(dsc, hdisplay);
 
 	eol_byte_num = total_bytes_per_intf % 3;
 	pkt_per_line = slice_per_intf / dsc->slice_count;
@@ -936,6 +937,12 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
 			return;
 		}
 
+		if (!dsc->slice_width || (mode->hdisplay < dsc->slice_width)) {
+			pr_err("DSI: invalid slice width %d (pic_width: %d)\n",
+			       dsc->slice_width, mode->hdisplay);
+			return;
+		}
+
 		dsc->pic_width = mode->hdisplay;
 		dsc->pic_height = mode->vdisplay;
 		DBG("Mode %dx%d\n", dsc->pic_width, dsc->pic_height);
@@ -1759,7 +1766,7 @@ static int dsi_populate_dsc_params(struct msm_dsi_host *msm_host, struct drm_dsc
 		return ret;
 	}
 
-	dsc->initial_scale_value = 32;
+	drm_dsc_set_initial_scale_value(dsc);
 	dsc->line_buf_depth = dsc->bits_per_component + 1;
 
 	return drm_dsc_compute_rc_parameters(dsc);

-- 
2.40.0

[PATCH v3 5/6] drm/msm/dsi: update hdisplay calculation for dsi_timing_setup

[Jessica Zhang]

hdisplay for compressed images should be calculated as bytes_per_slice *
slice_count. Thus, use MSM DSC helper to calculate hdisplay for
dsi_timing_setup instead of directly using mode->hdisplay.

Changes in v3:
- Split from previous patch
- Initialized hdisplay as uncompressed pclk per line at the beginning of
  dsi_timing_setup as to not break dual DSI calculations

Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 6a6218a9655f..9c33060e4c29 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -912,6 +912,9 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
 
 	DBG("");
 
+	if (msm_host->dsc)
+		hdisplay = msm_dsc_get_uncompressed_pclk_per_intf(msm_host->dsc);
+
 	/*
 	 * For bonded DSI mode, the current DRM mode has
 	 * the complete width of the panel. Since, the complete

-- 
2.40.0

[PATCH v3 6/6] drm/msm/dsi: Fix calculations pkt_per_line

[Jessica Zhang]

Currently, pkt_per_line is calculated by dividing slice_per_intf by
slice_count. This is incorrect, as slice_per_intf should be divided by
slice_per_pkt, which is not always equivalent to slice_count as it is
possible for there to be multiple soft slices per interface even though
a panel only specifies one slice per packet.

Fixes: 08802f515c3c ("drm/msm/dsi: Add support for DSC configuration")
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/gpu/drm/msm/dsi/dsi_host.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
index 9c33060e4c29..d888978926da 100644
--- a/drivers/gpu/drm/msm/dsi/dsi_host.c
+++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
@@ -862,7 +862,11 @@ static void dsi_update_dsc_timing(struct msm_dsi_host *msm_host, bool is_cmd_mod
 	total_bytes_per_intf = msm_dsc_get_bytes_per_intf(dsc, hdisplay);
 
 	eol_byte_num = total_bytes_per_intf % 3;
-	pkt_per_line = slice_per_intf / dsc->slice_count;
+
+	/* Default to 1 slice_per_pkt, so pkt_per_line will be equal to
+	 * slice per intf.
+	 */
+	pkt_per_line = slice_per_intf;
 
 	if (is_cmd_mode) /* packet data type */
 		reg = DSI_COMMAND_COMPRESSION_MODE_CTRL_STREAM0_DATATYPE(MIPI_DSI_DCS_LONG_WRITE);

-- 
2.40.0

Re: [PATCH v3 1/6] drm/msm: Add MSM-specific DSC helper methods

[Abhinav Kumar]

On 4/4/2023 4:56 PM, Jessica Zhang wrote:
> Introduce MSM-specific DSC helper methods, as some calculations are
> common between DP and DSC.
> 
> Changes in v2:
> - Moved files up to msm/ directory
> - Dropped get_comp_ratio() helper
> - Used drm_int2fixp() to convert to integers to fp
> - Style changes to improve readability
> - Dropped unused bpp variable in msm_dsc_get_dce_bytes_per_line()
> - Changed msm_dsc_get_slice_per_intf() to a static inline method
> - Dropped last division step of msm_dsc_get_pclk_per_line() and changed
>    method name accordingly
> - Changed DSC_BPP macro to drm_dsc_get_bpp_int() helper method
> - Fixed some math issues caused by passing in incorrect types to
>    drm_fixed methods in get_bytes_per_soft_slice()
> 
> Changes in v3:
> - Dropped src_bpp parameter from all methods -- src_bpp can be
>    calculated as dsc->bits_per_component * 3
> - Dropped intf_width parameter from get_bytes_per_soft_slice()
> - Moved dsc->bits_per_component to numerator calculation in
>    get_bytes_per_soft_slice()
> - Renamed msm_dsc_get_uncompressed_pclk_per_line to
>    *_get_uncompressed_pclk_per_intf()
> - Removed dsc->slice_width check from
>    msm_dsc_get_uncompressed_pclk_per_intf()
> - Made get_bytes_per_soft_slice() a public method (this will be called
>    later to help calculate DP pclk params)
> - Added documentation in comments
> - Moved extra_eol_bytes math out of msm_dsc_get_eol_byte_num() and
>    renamed msm_dsc_get_eol_byte_num to *_get_bytes_per_intf.
> 
> Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
> ---
>   drivers/gpu/drm/msm/Makefile         |  1 +
>   drivers/gpu/drm/msm/msm_dsc_helper.c | 47 ++++++++++++++++++++++++
>   drivers/gpu/drm/msm/msm_dsc_helper.h | 70 ++++++++++++++++++++++++++++++++++++
>   3 files changed, 118 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/Makefile b/drivers/gpu/drm/msm/Makefile
> index 7274c41228ed..b814fc80e2d5 100644
> --- a/drivers/gpu/drm/msm/Makefile
> +++ b/drivers/gpu/drm/msm/Makefile
> @@ -94,6 +94,7 @@ msm-y += \
>   	msm_atomic_tracepoints.o \
>   	msm_debugfs.o \
>   	msm_drv.o \
> +	msm_dsc_helper.o \
>   	msm_fb.o \
>   	msm_fence.o \
>   	msm_gem.o \
> diff --git a/drivers/gpu/drm/msm/msm_dsc_helper.c b/drivers/gpu/drm/msm/msm_dsc_helper.c
> new file mode 100644
> index 000000000000..c8c530211f50
> --- /dev/null
> +++ b/drivers/gpu/drm/msm/msm_dsc_helper.c
> @@ -0,0 +1,47 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <drm/drm_fixed.h>
> +
> +#include "msm_drv.h"
> +#include "msm_dsc_helper.h"
> +
> +s64 get_bytes_per_soft_slice(struct drm_dsc_config *dsc)
> +{
> +	int bpp = msm_dsc_get_bpp_int(dsc);
> +	s64 numerator_fp, denominator_fp;
> +	s64 comp_ratio_fp = drm_fixp_from_fraction(dsc->bits_per_component * 3, bpp);
> +
> +	numerator_fp = drm_int2fixp(dsc->slice_width * 3 * dsc->bits_per_component);
> +	denominator_fp = drm_fixp_mul(comp_ratio_fp, drm_int2fixp(8));
> +
> +	return drm_fixp_div(numerator_fp, denominator_fp);
> +}
> +
> +u32 msm_dsc_get_bytes_per_intf(struct drm_dsc_config *dsc, int intf_width)
> +{
> +	u32 bytes_per_soft_slice, bytes_per_intf;
> +	s64 bytes_per_soft_slice_fp;
> +	int slice_per_intf = msm_dsc_get_slice_per_intf(dsc, intf_width);
> +
> +	bytes_per_soft_slice_fp = get_bytes_per_soft_slice(dsc);
> +	bytes_per_soft_slice = drm_fixp2int_ceil(bytes_per_soft_slice_fp);
> +
> +	bytes_per_intf = bytes_per_soft_slice * slice_per_intf;
> +
> +	return bytes_per_intf;
> +}
> +
> +int msm_dsc_get_uncompressed_pclk_per_intf(struct drm_dsc_config *dsc)
> +{
> +	s64 data_width;
> +
> +	data_width = drm_fixp_mul(drm_int2fixp(dsc->slice_count),
> +			get_bytes_per_soft_slice(dsc));
> +
> +	return drm_fixp2int_ceil(data_width);
> +}

This is not really uncompressed pclk_per_intf. This is still calculated 
using the compression ratio so it is still compressed.

I would suggest changing this to msm_dsc_get_pclk_per_intf().

Lets keep it simple.

> diff --git a/drivers/gpu/drm/msm/msm_dsc_helper.h b/drivers/gpu/drm/msm/msm_dsc_helper.h
> new file mode 100644
> index 000000000000..5ee972eb247c
> --- /dev/null
> +++ b/drivers/gpu/drm/msm/msm_dsc_helper.h
> @@ -0,0 +1,70 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (c) 2023 Qualcomm Innovation Center, Inc. All rights reserved
> + */
> +
> +#ifndef MSM_DSC_HELPER_H_
> +#define MSM_DSC_HELPER_H_
> +
> +#include <drm/display/drm_dsc_helper.h>
> +#include <drm/drm_modes.h>
> +
> +/*
> + * Helper methods for MSM specific DSC calculations that are common between timing engine,
> + * DSI, and DP.
> + */
> +
> +/**
> + * msm_dsc_get_bpp_int - get bits per pixel integer value
> + * @dsc: Pointer to drm dsc config struct
> + */
> +static inline int msm_dsc_get_bpp_int(struct drm_dsc_config *dsc)
> +{
> +	WARN_ON_ONCE(dsc->bits_per_pixel & 0xf);
> +	return dsc->bits_per_pixel >> 4;
> +}
> +
> +/**
> + * msm_dsc_get_slice_per_intf - get number of slices per interface
> + * @dsc: Pointer to drm dsc config struct
> + * @intf_width: interface width
> + */
> +static inline int msm_dsc_get_slice_per_intf(struct drm_dsc_config *dsc, int intf_width)
> +{
> +	return DIV_ROUND_UP(intf_width, dsc->slice_width);
> +}
> +
> +/**
> + * msm_dsc_get_dce_bytes_per_line - get bytes per line to help calculate data width
> + *	when configuring the timing engine
> + * @dsc: Pointer to drm dsc config struct
> + * @intf_width: interface width
> + */
> +static inline u32 msm_dsc_get_dce_bytes_per_line(struct drm_dsc_config *dsc, int intf_width)
> +{
> +	return DIV_ROUND_UP(msm_dsc_get_bpp_int(dsc) * intf_width, 8);
> +}
> +
> +/**
> + * get_bytes_per_soft_slice - get size of each soft slice for dsc
> + * @dsc: Pointer to drm dsc config struct
> + */
> +s64 get_bytes_per_soft_slice(struct drm_dsc_config *dsc);
> +
> +/**
> + * msm_dsc_get_bytes_per_intf - get total bytes per interface
> + * @dsc: Pointer to drm dsc config struct
> + * @intf_width: interface width
> + */
> +u32 msm_dsc_get_bytes_per_intf(struct drm_dsc_config *dsc, int intf_width);
> +
> +/**
> + * msm_dsc_get_uncompressed_pclk_per_intf - Calculate uncompressed pclk per line.
> + * @dsc: Pointer to drm dsc config struct
> + *
> + * Note: This value will then be passed along to DSI and DP to calculate pclk_per_intf.
> + * This is because DSI and DP divide the uncompressed pclk_per_intf by different
> + * values depending on if widebus is enabled.
> + */
> +int msm_dsc_get_uncompressed_pclk_per_intf(struct drm_dsc_config *dsc);
> +#endif /* MSM_DSC_HELPER_H_ */
> 

Re: [PATCH v3 5/6] drm/msm/dsi: update hdisplay calculation for dsi_timing_setup

[Abhinav Kumar]

On 4/4/2023 4:56 PM, Jessica Zhang wrote:
> hdisplay for compressed images should be calculated as bytes_per_slice *
> slice_count. Thus, use MSM DSC helper to calculate hdisplay for
> dsi_timing_setup instead of directly using mode->hdisplay.
> 
> Changes in v3:
> - Split from previous patch
> - Initialized hdisplay as uncompressed pclk per line at the beginning of
>    dsi_timing_setup as to not break dual DSI calculations
> 
> Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
> ---
>   drivers/gpu/drm/msm/dsi/dsi_host.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi_host.c b/drivers/gpu/drm/msm/dsi/dsi_host.c
> index 6a6218a9655f..9c33060e4c29 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi_host.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi_host.c
> @@ -912,6 +912,9 @@ static void dsi_timing_setup(struct msm_dsi_host *msm_host, bool is_bonded_dsi)
>   
>   	DBG("");
>   
> +	if (msm_host->dsc)
> +		hdisplay = msm_dsc_get_uncompressed_pclk_per_intf(msm_host->dsc);
> +

bonded-dsi with DSC is really not a tested configuration. If you move 
this line to before the if (is_bonded_dsi), then you will be dividing /2 
on a compressed value. That wont make sense.

I would still move this back to the if (msm_host->dsc) that way, 
bonded_dsi first divides hdisplay/2 on an uncompressed mode->hdisplay 
then DSC does its math on top of that.

>   	/*
>   	 * For bonded DSI mode, the current DRM mode has
>   	 * the complete width of the panel. Since, the complete
>