Re: [PATCH v7 05/18] drm/mediatek: Set DRM mode configs accordingly

[Fei Shao]

On Mon, May 27, 2024 at 12:38 PM Chen-Yu Tsai <wens@xxxxxxxxxx> wrote:
>
> On Mon, May 27, 2024 at 12:34 PM Fei Shao <fshao@xxxxxxxxxxxx> wrote:
> >
> > Hi Shawn,
> >
> > On Thu, May 2, 2024 at 6:39 PM Shawn Sung <shawn.sung@xxxxxxxxxxxx> wrote:
> > >
> > > From: Hsiao Chien Sung <shawn.sung@xxxxxxxxxxxx>
> > >
> > > Set DRM mode configs limitation according to the hardware capabilities
> > > and pass the IGT checks as below:
> > >
> > > - The test "graphics.IgtKms.kms_plane" requires a frame buffer with
> > >   width of 4512 pixels (> 4096).
> > > - The test "graphics.IgtKms.kms_cursor_crc" checks if the cursor size is
> > >   defined, and run the test with cursor size from 1x1 to 512x512.
> > >
> > > Please notice that the test conditions may change as IGT is updated.
> > >
> > > Signed-off-by: Hsiao Chien Sung <shawn.sung@xxxxxxxxxxxx>
> > > ---
> > >  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 22 ++++++++++++++++++++++
> > >  drivers/gpu/drm/mediatek/mtk_drm_drv.h |  4 ++++
> > >  2 files changed, 26 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > > index 8e047043202b4..c9cad3a827376 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > > +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> > > @@ -294,6 +294,9 @@ static const struct mtk_mmsys_driver_data mt8188_vdosys0_driver_data = {
> > >         .conn_routes = mt8188_mtk_ddp_main_routes,
> > >         .num_conn_routes = ARRAY_SIZE(mt8188_mtk_ddp_main_routes),
> > >         .mmsys_dev_num = 2,
> > > +       .max_width = 8191,
> > > +       .min_width = 1,
> > > +       .min_height = 1,
> > >  };
> > >
> > >  static const struct mtk_mmsys_driver_data mt8192_mmsys_driver_data = {
> > > @@ -308,6 +311,9 @@ static const struct mtk_mmsys_driver_data mt8195_vdosys0_driver_data = {
> > >         .main_path = mt8195_mtk_ddp_main,
> > >         .main_len = ARRAY_SIZE(mt8195_mtk_ddp_main),
> > >         .mmsys_dev_num = 2,
> > > +       .max_width = 8191,
> > > +       .min_width = 1,
> > > +       .min_height = 1,
> > >  };
> > >
> > >  static const struct mtk_mmsys_driver_data mt8195_vdosys1_driver_data = {
> > > @@ -315,6 +321,9 @@ static const struct mtk_mmsys_driver_data mt8195_vdosys1_driver_data = {
> > >         .ext_len = ARRAY_SIZE(mt8195_mtk_ddp_ext),
> > >         .mmsys_id = 1,
> > >         .mmsys_dev_num = 2,
> > > +       .max_width = 8191,
> > > +       .min_width = 2, /* 2-pixel align when ethdr is bypassed */
> > > +       .min_height = 1,
> > >  };
> > >
> > >  static const struct of_device_id mtk_drm_of_ids[] = {
> > > @@ -493,6 +502,15 @@ static int mtk_drm_kms_init(struct drm_device *drm)
> > >                 for (j = 0; j < private->data->mmsys_dev_num; j++) {
> > >                         priv_n = private->all_drm_private[j];
> > >
> > > +                       if (priv_n->data->max_width)
> > > +                               drm->mode_config.max_width = priv_n->data->max_width;
> > > +
> > > +                       if (priv_n->data->min_width)
> > > +                               drm->mode_config.min_width = priv_n->data->min_width;
> > > +
> > > +                       if (priv_n->data->min_height)
> > > +                               drm->mode_config.min_height = priv_n->data->min_height;
> > > +
> > >                         if (i == CRTC_MAIN && priv_n->data->main_len) {
> > >                                 ret = mtk_crtc_create(drm, priv_n->data->main_path,
> > >                                                       priv_n->data->main_len, j,
> > > @@ -520,6 +538,10 @@ static int mtk_drm_kms_init(struct drm_device *drm)
> > >                 }
> > >         }
> > >
> > > +       /* IGT will check if the cursor size is configured */
> > > +       drm->mode_config.cursor_width = drm->mode_config.max_width;
> > > +       drm->mode_config.cursor_height = drm->mode_config.max_height;
> >
> > I think you shouldn't set the cursor size to the maximum plane size.
> > As you mentioned in the commit message, IGT tests the cursor sizes
> > from 1x1 to 512x512, so just setting them to 512 (with a macro) should
> > be enough.
> >
> > Currently this tells the userspace "the supported cursor plane size is
> > up to 4096x8191" on MT8195 and MT8188.
> > That means the userspace may allocate a buffer with 4096*8191*4 ~=
> > 128MB for the cursor plane in the worst case, and most of the buffer
> > will be wasted.
> > Note that the default value for DRM_CAP_CURSOR_WIDTH is 64.
> >
> > In practice, when applying this on the MT8188 Chromebook, I see the
> > userspace allocates two 64MB buffers for the cursor plane.
> > But if I limit the cursor size to 512, the userspace only allocates
> > two 1MB buffers i.e. 126MB is optimized for the DMA buffer allocation.
>
> That seems more like an issue of ChromeOS not doing the most optimal
> thing though?

I agree that we need to fix this on the ChromeOS side too, but I still
think the driver doesn't need to set the capabilities like this
because a full-screen size cursor is not practical anyway.
The default cursor plane size is just 64x64.

Regard,
Fei



>
> > Regards,
> > Fei
> >
> >
> > >
> > > +
> > >         /* Use OVL device for all DMA memory allocations */
> > >         crtc = drm_crtc_from_index(drm, 0);
> > >         if (crtc)
> > > diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.h b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> > > index 78d698ede1bf8..6cfa790e8df5c 100644
> > > --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> > > +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> > > @@ -46,6 +46,10 @@ struct mtk_mmsys_driver_data {
> > >         bool shadow_register;
> > >         unsigned int mmsys_id;
> > >         unsigned int mmsys_dev_num;
> > > +
> > > +       int max_width;
> > > +       int min_width;
> > > +       int min_height;
> > >  };
> > >
> > >  struct mtk_drm_private {
> > > --
> > > 2.18.0
> > >