On 9/19/26 08:52, Chaoyi Chen wrote:
Hi,
On 9/16/2026 7:08 PM, AngeloGioacchino Del Regno wrote:
Add a real driver for the Display Stream Compression (DSC) Display
Controller IP, implementing support for DSC v1.1 to v1.2.
In order to do this, it was necessary to remove the basic DSC IP
bypass setup from mtk_ddp_comp: this functionality is retained in
the new mtk_disp_dsc driver, which checks if DSC was actually
requested by other components (with the only one that currently
supports this being DSI) and, if not, it will set BYPASS mode in
the DSC IP.
Like before, the BYPASS mode is set before starting the DSC IP,
but unlike before, this is being done in the component start
callback instead of the config one.
Notably, the config callback is called by mtk_crtc always
immediately before the calling start callback, so the order of
register writes is retained.
The only real difference is that now this is being done through
CPU writes instead of CMDQ, but since that's called only once
and since it's just three registers, the performance impact will
not be minimal and not even measurable.
As anticipated, DSC handling was also introduced in the mtk_dsi
driver: when performing dsi_host_attach, the driver now checks
if the DSI panel adds the DSC configuration structure to the
mipi_dsi_device structure and, if it does, it will store a
pointer in the driver-local mtk_dsi structure's `dsc` member.
The DSI driver will then check whether the DSC configuration
that comes from the panel is valid (in regard to MediaTek DSI)
and will call the DRM API's DSC helpers to calculate and set
all of the const and RC parameters for the actual DSC setup.
For the time being, even though the latest MediaTek SoCs do
support DSC v1.2, only DSC v1.1 pre-scr support is implemented
as an initial contribution (which is rather big, and 1.2 would
make it even bigger - but that can anyway be implemented later).
As a last step for validation of DSC parameters in DSI, a check
for the hdisplay against DSC slice sidth and one for vdisplay
against DSC slice height was added to the mode_valid callback,
making sure that H/V are, as expected, multiples of slice W/H.
Signed-off-by: AngeloGioacchino Del Regno
<[email protected]>
---
drivers/gpu/drm/mediatek/Makefile | 1 +
drivers/gpu/drm/mediatek/mtk_crtc.c | 21 ++
drivers/gpu/drm/mediatek/mtk_ddp_comp.c | 43 +--
drivers/gpu/drm/mediatek/mtk_ddp_comp.h | 9 +
drivers/gpu/drm/mediatek/mtk_disp_drv.h | 8 +
drivers/gpu/drm/mediatek/mtk_disp_dsc.c | 449 ++++++++++++++++++++++++
drivers/gpu/drm/mediatek/mtk_drm_drv.c | 2 +
drivers/gpu/drm/mediatek/mtk_drm_drv.h | 1 +
drivers/gpu/drm/mediatek/mtk_dsi.c | 151 +++++++-
9 files changed, 635 insertions(+), 50 deletions(-)
create mode 100644 drivers/gpu/drm/mediatek/mtk_disp_dsc.c
[...]
+
+ dsc->simple_422 = false;
+ dsc->convert_rgb = true;
+ dsc->vbr_enable = false;
+
+ drm_dsc_set_const_params(dsc);
+ drm_dsc_set_rc_buf_thresh(dsc);
+
+ ret = drm_dsc_setup_rc_params(dsc, DRM_DSC_1_2_444);
+ if (ret) {
+ dev_err(dev, "Cannot find DSC RC params\n");
+ return ret;
+ }
+
Just out of curiosity, is there a reason the DSC v1.1 rc parameters
aren't used here?
I was using the v1.1 RC parameters before, but Nikolai found out that some
panels
actually require that, even when v1.2 support is not declared.
Besides, he also validated that v1.2 works for him, and works for me as well, so
I opted to use those ones instead, as the v1.1 pre_scr params were working for
me
but not for him.
This will be improved in the future, as choosing any of the two will leave us
with
something working and something broken... but I plan to make those improvements
only after at least this basic support finds his way upstream.
Cheers,
Angelo
