Re: [Intel-gfx] [PATCH v5 16/19] uapi/drm/dg2: Introduce format modifier for DG2 clear color

["Chery, Nanley G" <nanley.g.chery@intel.com>]

> -----Original Message-----
> From: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> Sent: Tuesday, February 15, 2022 9:32 AM
> To: Chery, Nanley G <nanley.g.chery@intel.com>; Nanley Chery
> <nanleychery@gmail.com>; C, Ramalingam <ramalingam.c@intel.com>
> Cc: intel-gfx <intel-gfx@lists.freedesktop.org>; Auld, Matthew
> <matthew.auld@intel.com>; dri-devel <dri-devel@lists.freedesktop.org>
> Subject: Re: [Intel-gfx] [PATCH v5 16/19] uapi/drm/dg2: Introduce format
> modifier for DG2 clear color
> 
> On 15.2.2022 18.44, Chery, Nanley G wrote:
> >
> >
> >> -----Original Message-----
> >> From: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> >> Sent: Tuesday, February 15, 2022 8:15 AM
> >> To: Chery, Nanley G <nanley.g.chery@intel.com>; Nanley Chery
> >> <nanleychery@gmail.com>; C, Ramalingam <ramalingam.c@intel.com>
> >> Cc: intel-gfx <intel-gfx@lists.freedesktop.org>; Auld, Matthew
> >> <matthew.auld@intel.com>; dri-devel <dri-devel@lists.freedesktop.org>
> >> Subject: Re: [Intel-gfx] [PATCH v5 16/19] uapi/drm/dg2: Introduce
> >> format modifier for DG2 clear color
> >>
> >> On 15.2.2022 17.02, Chery, Nanley G wrote:
> >>>
> >>>
> >>>> -----Original Message-----
> >>>> From: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
> >>>> Sent: Tuesday, February 15, 2022 6:56 AM
> >>>> To: Nanley Chery <nanleychery@gmail.com>; C, Ramalingam
> >>>> <ramalingam.c@intel.com>
> >>>> Cc: intel-gfx <intel-gfx@lists.freedesktop.org>; Chery, Nanley G
> >>>> <nanley.g.chery@intel.com>; Auld, Matthew <matthew.auld@intel.com>;
> >>>> dri- devel <dri-devel@lists.freedesktop.org>
> >>>> Subject: Re: [Intel-gfx] [PATCH v5 16/19] uapi/drm/dg2: Introduce
> >>>> format modifier for DG2 clear color
> >>>>
> >>>> On 12.2.2022 3.19, Nanley Chery wrote:
> >>>>> On Tue, Feb 1, 2022 at 2:42 AM Ramalingam C
> >>>>> <ramalingam.c@intel.com>
> >>>> wrote:
> >>>>>>
> >>>>>> From: Mika Kahola <mika.kahola@intel.com>
> >>>>>>
> >>>>>> DG2 clear color render compression uses Tile4 layout. Therefore,
> >>>>>> we need to define a new format modifier for uAPI to support clear
> >>>>>> color
> >>>> rendering.
> >>>>>>
> >>>>>> v2:
> >>>>>>      Display version is fixed. [Imre]
> >>>>>>      KDoc is enhanced for cc modifier. [Nanley & Lionel]
> >>>>>>
> >>>>>> Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> >>>>>> cc: Anshuman Gupta <anshuman.gupta@intel.com>
> >>>>>> Signed-off-by: Juha-Pekka Heikkilä
> >>>>>> <juha-pekka.heikkila@intel.com>
> >>>>>> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
> >>>>>> ---
> >>>>>>     drivers/gpu/drm/i915/display/intel_fb.c            |  8 ++++++++
> >>>>>>     drivers/gpu/drm/i915/display/skl_universal_plane.c |  9 ++++++++-
> >>>>>>     include/uapi/drm/drm_fourcc.h                      | 10 ++++++++++
> >>>>>>     3 files changed, 26 insertions(+), 1 deletion(-)
> >>>>>>
> >>>>>> diff --git a/drivers/gpu/drm/i915/display/intel_fb.c
> >>>>>> b/drivers/gpu/drm/i915/display/intel_fb.c
> >>>>>> index 4d4d01963f15..3df6ef5ffec5 100644
> >>>>>> --- a/drivers/gpu/drm/i915/display/intel_fb.c
> >>>>>> +++ b/drivers/gpu/drm/i915/display/intel_fb.c
> >>>>>> @@ -144,6 +144,12 @@ static const struct intel_modifier_desc
> >>>> intel_modifiers[] = {
> >>>>>>                    .modifier = I915_FORMAT_MOD_4_TILED_DG2_MC_CCS,
> >>>>>>                    .display_ver = { 13, 13 },
> >>>>>>                    .plane_caps = INTEL_PLANE_CAP_TILING_4 |
> >>>>>> INTEL_PLANE_CAP_CCS_MC,
> >>>>>> +       }, {
> >>>>>> +               .modifier = I915_FORMAT_MOD_4_TILED_DG2_RC_CCS_CC,
> >>>>>> +               .display_ver = { 13, 13 },
> >>>>>> +               .plane_caps = INTEL_PLANE_CAP_TILING_4 |
> >>>>>> + INTEL_PLANE_CAP_CCS_RC_CC,
> >>>>>> +
> >>>>>> +               .ccs.cc_planes = BIT(1),
> >>>>>>            }, {
> >>>>>>                    .modifier = I915_FORMAT_MOD_4_TILED_DG2_RC_CCS,
> >>>>>>                    .display_ver = { 13, 13 }, @@ -559,6 +565,7 @@
> >>>>>> intel_tile_width_bytes(const struct drm_framebuffer *fb, int
> color_plane)
> >>>>>>                    else
> >>>>>>                            return 512;
> >>>>>>            case I915_FORMAT_MOD_4_TILED_DG2_RC_CCS:
> >>>>>> +       case I915_FORMAT_MOD_4_TILED_DG2_RC_CCS_CC:
> >>>>>>            case I915_FORMAT_MOD_4_TILED_DG2_MC_CCS:
> >>>>>>            case I915_FORMAT_MOD_4_TILED:
> >>>>>>                    /*
> >>>>>> @@ -763,6 +770,7 @@ unsigned int intel_surf_alignment(const
> >>>>>> struct
> >>>> drm_framebuffer *fb,
> >>>>>>            case I915_FORMAT_MOD_Yf_TILED:
> >>>>>>                    return 1 * 1024 * 1024;
> >>>>>>            case I915_FORMAT_MOD_4_TILED_DG2_RC_CCS:
> >>>>>> +       case I915_FORMAT_MOD_4_TILED_DG2_RC_CCS_CC:
> >>>>>>            case I915_FORMAT_MOD_4_TILED_DG2_MC_CCS:
> >>>>>>                    return 16 * 1024;
> >>>>>>            default:
> >>>>>> diff --git a/drivers/gpu/drm/i915/display/skl_universal_plane.c
> >>>>>> b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> >>>>>> index c38ae0876c15..b4dced1907c5 100644
> >>>>>> --- a/drivers/gpu/drm/i915/display/skl_universal_plane.c
> >>>>>> +++ b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> >>>>>> @@ -772,6 +772,8 @@ static u32 skl_plane_ctl_tiling(u64 fb_modifier)
> >>>>>>                    return PLANE_CTL_TILED_4 |
> >>>>>>                            PLANE_CTL_MEDIA_DECOMPRESSION_ENABLE |
> >>>>>>                            PLANE_CTL_CLEAR_COLOR_DISABLE;
> >>>>>> +       case I915_FORMAT_MOD_4_TILED_DG2_RC_CCS_CC:
> >>>>>> +               return PLANE_CTL_TILED_4 |
> >>>>>> + PLANE_CTL_RENDER_DECOMPRESSION_ENABLE;
> >>>>>>            case I915_FORMAT_MOD_Y_TILED_CCS:
> >>>>>>            case I915_FORMAT_MOD_Y_TILED_GEN12_RC_CCS_CC:
> >>>>>>                    return PLANE_CTL_TILED_Y |
> >>>>>> PLANE_CTL_RENDER_DECOMPRESSION_ENABLE;
> >>>>>> @@ -2358,10 +2360,15 @@ skl_get_initial_plane_config(struct
> >>>>>> intel_crtc
> >>>> *crtc,
> >>>>>>                    break;
> >>>>>>            case PLANE_CTL_TILED_YF: /* aka PLANE_CTL_TILED_4 on XE_LPD+
> */
> >>>>>>                    if (HAS_4TILE(dev_priv)) {
> >>>>>> -                       if (val & PLANE_CTL_RENDER_DECOMPRESSION_ENABLE)
> >>>>>> +                       u32 rc_mask =
> >> PLANE_CTL_RENDER_DECOMPRESSION_ENABLE |
> >>>>>> +
> >>>>>> + PLANE_CTL_CLEAR_COLOR_DISABLE;
> >>>>>> +
> >>>>>> +                       if ((val & rc_mask) == rc_mask)
> >>>>>>                                    fb->modifier =
> >> I915_FORMAT_MOD_4_TILED_DG2_RC_CCS;
> >>>>>>                            else if (val &
> PLANE_CTL_MEDIA_DECOMPRESSION_ENABLE)
> >>>>>>                                    fb->modifier =
> >>>>>> I915_FORMAT_MOD_4_TILED_DG2_MC_CCS;
> >>>>>> +                       else if (val &
> PLANE_CTL_RENDER_DECOMPRESSION_ENABLE)
> >>>>>> +                               fb->modifier =
> >>>>>> + I915_FORMAT_MOD_4_TILED_DG2_RC_CCS_CC;
> >>>>>>                            else
> >>>>>>                                    fb->modifier = I915_FORMAT_MOD_4_TILED;
> >>>>>>                    } else {
> >>>>>> diff --git a/include/uapi/drm/drm_fourcc.h
> >>>>>> b/include/uapi/drm/drm_fourcc.h index b8fb7b44c03c..697614ea4b84
> >>>>>> 100644
> >>>>>> --- a/include/uapi/drm/drm_fourcc.h
> >>>>>> +++ b/include/uapi/drm/drm_fourcc.h
> >>>>>> @@ -605,6 +605,16 @@ extern "C" {
> >>>>>>      */
> >>>>>>     #define I915_FORMAT_MOD_4_TILED_DG2_MC_CCS
> >>>> fourcc_mod_code(INTEL,
> >>>>>> 11)
> >>>>>>
> >>>>>> +/*
> >>>>>> + * Intel color control surfaces (CCS) for DG2 clear color render
> >> compression.
> >>>>>> + *
> >>>>>> + * DG2 uses a unified compression format for clear color render
> >>>> compression.
> >>>>>
> >>>>> What's unified about DG2's compression format? If this doesn't
> >>>>> affect the layout, maybe we should drop this sentence.
> >>>>>
> >>>>>> + * The general layout is a tiled layout using 4Kb tiles i.e. Tile4 layout.
> >>>>>> + *
> >>>>>
> >>>>> This also needs a pitch aligned to four tiles, right? I think we
> >>>>> can save some effort by referencing the DG2_RC_CCS modifier here.
> >>>>>
> >>>>>> + * Fast clear color value expected by HW is located in fb at
> >>>>>> + offset
> >>>>>> + 0 of plane#1
> >>>>>
> >>>>> Why is the expected offset hardcoded to 0 instead of relying on
> >>>>> the offset provided by the modifier API? This looks like a bug.
> >>>>
> >>>> Hi Nanley,
> >>>>
> >>>> can you elaborate a bit, which offset from modifier API that
> >>>> applies to cc
> >> surface?
> >>>>
> >>>
> >>> Hi Juha-Pekka,
> >>>
> >>> On the kernel-side of things, I'm thinking of
> drm_mode_fb_cmd2::offsets[1].
> >>>
> >>
> >> Hi Nanley,
> >>
> >> this offset is coming from userspace on creation of framebuffer, at
> >> that moment from userspace caller can point to offset of desire.
> >> Normally offset[0] is set at 0 and then offset[n] at plane n start
> >> which is not stated to have to be exactly after plane n-1 end. Or did I
> misunderstand what you meant?
> >>
> >
> > Perhaps, at least, I'm not sure what you're meaning to say. This
> > modifier description seems to say that the drm_mode_fb_cmd2::offsets
> > value for the clear color plane must be zero. Are you saying that it's
> > correct? This doesn't match the GEN12_RC_CCS_CC behavior and doesn't
> match mesa's expectations.
> >
> 
> It doesn't say "drm_mode_fb_cmd2::offsets value for the clear color plane must
> be zero", it says "Fast clear color value expected by HW is located in fb at offset 0
> of plane#1".
> 

Yes, it doesn't say that exactly, but that's what it seems to say. With every other
modifier, it's implied that the data for the plane begins at the offset specified
through the modifier API. So, explicitly mentioning it here (and with that wording)
conveys a new requirement.

> Plane#1 location is pointed by drm_mode_fb_cmd2::offsets[1] and there's
> nothing stated about that offset.
> 

Technically, plane #1's location is specified to be the combination of ::handles[1]
and ::offsets[1]. In practice though, I can imagine that there are areas of the stack
that are implicitly requiring that all ::handles[] entries match.

> These offsets are just offsets to bo which contain the framebuffer information
> hence drm_mode_fb_cmd2::offsets[1] can be changed as one wish and cc
> information is found starting at drm_mode_fb_cmd2::offsets[1][0]
> 

If the clear color handling is the same as GEN12_RC_CCS_CC (apart for the plane
index), I propose that we drop this sentence due to avoid any confusion.

This offset discussion raises another question. The description says that the value
expected by HW is at offset 0. I'm assuming "HW" is referring to the render engine?
The kernel is still giving the display engine the packed values at ::offsets[1] + 16B right?

-Nanley

> /Juha-Pekka
> 
> >
> >> For cc plane this offset likely will not be zero anyway and caller
> >> can move it as see fit to have cc plane (plane[1]) location[0] at place where
> wanted to have it.
> >>
> >> /Juha-Pekka
> >>
> >>>
> >>>>>
> >>>>> We should probably give some info about the relevant fields in the
> >>>>> fast clear plane (like what's done in the GEN12_RC_CCS_CC modifier).
> >>>>
> >>>> agree, that's totally missing here.
> >>>>
> >>>> /Juha-Pekka
> >>>>
> >>>>>
> >>>>>> + */
> >>>>>> +#define I915_FORMAT_MOD_4_TILED_DG2_RC_CCS_CC
> >>>> fourcc_mod_code(INTEL,
> >>>>>> +12)
> >>>>>> +
> >>>>>>     /*
> >>>>>>      * Tiled, NV12MT, grouped in 64 (pixels) x 32 (lines) -sized macroblocks
> >>>>>>      *
> >>>>>> --
> >>>>>> 2.20.1
> >>>>>>
> >>>
> >