linux-kernel - Re: [PATCH] drm/tegra: add tiling FB modifiers

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Message-ID: <20170320172635.GD14787@ulmo.ba.sec>
Date:   Mon, 20 Mar 2017 18:26:35 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Alexandre Courbot <acourbot@...dia.com>
Cc:     kusmabite@...il.com, David Airlie <airlied@...ux.ie>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        linux-kernel@...r.kernel.org, Alexandre Courbot <gnurou@...il.com>
Subject: Re: [PATCH] drm/tegra: add tiling FB modifiers

On Tue, Nov 08, 2016 at 06:19:01PM +0900, Alexandre Courbot wrote:
> On 11/08/2016 06:07 PM, Erik Faye-Lund wrote:
> > On Tue, Nov 8, 2016 at 8:50 AM, Alexandre Courbot <acourbot@...dia.com> wrote:
> >> Add FB modifiers to allow user-space to specify that a surface is in one
> >> of the two tiling formats supported by Tegra chips, and add support in
> >> the tegradrm driver to handle them properly. This is necessary for the
> >> display controller to directly display buffers generated by the GPU.
> >>
> >> This feature is intended to replace the dedicated IOCTL enabled
> >> by TEGRA_STAGING and to provide a non-staging alternative to that
> >> solution.
> >>
> >> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> >> ---
> >>  drivers/gpu/drm/tegra/drm.c   |  2 ++
> >>  drivers/gpu/drm/tegra/fb.c    | 23 +++++++++++++++++++---
> >>  include/uapi/drm/drm_fourcc.h | 45 +++++++++++++++++++++++++++++++++++++++++++
> >>  3 files changed, 67 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
> >> index a9630c2d6cb3..36b4b30a5164 100644
> >> --- a/drivers/gpu/drm/tegra/drm.c
> >> +++ b/drivers/gpu/drm/tegra/drm.c
> >> @@ -161,6 +161,8 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
> >>         drm->mode_config.max_width = 4096;
> >>         drm->mode_config.max_height = 4096;
> >>
> >> +       drm->mode_config.allow_fb_modifiers = true;
> >> +
> >>         drm->mode_config.funcs = &tegra_drm_mode_funcs;
> >>
> >>         err = tegra_drm_fb_prepare(drm);
> >> diff --git a/drivers/gpu/drm/tegra/fb.c b/drivers/gpu/drm/tegra/fb.c
> >> index e6d71fa4028e..2fded58b2ca5 100644
> >> --- a/drivers/gpu/drm/tegra/fb.c
> >> +++ b/drivers/gpu/drm/tegra/fb.c
> >> @@ -52,9 +52,26 @@ int tegra_fb_get_tiling(struct drm_framebuffer *framebuffer,
> >>                         struct tegra_bo_tiling *tiling)
> >>  {
> >>         struct tegra_fb *fb = to_tegra_fb(framebuffer);
> >> -
> >> -       /* TODO: handle YUV formats? */
> >> -       *tiling = fb->planes[0]->tiling;
> >> +       uint64_t modifier = fb->base.modifier[0];
> >> +
> >> +       switch (fourcc_mod_tegra_mod(modifier)) {
> >> +       case NV_FORMAT_MOD_TEGRA_TILED:
> >> +               tiling->mode = TEGRA_BO_TILING_MODE_TILED;
> >> +               tiling->value = 0;
> >> +               break;
> >> +
> >> +       case NV_FORMAT_MOD_TEGRA_16BX2_BLOCK(0):
> >> +               tiling->mode = TEGRA_BO_TILING_MODE_BLOCK;
> >> +               tiling->value = fourcc_mod_tegra_param(modifier);
> >> +               if (tiling->value > 5)
> >> +                       return -EINVAL;
> > 
> > Shouldn't this contain some hardware-check for the support? AFAIK, not
> > all Tegras support all block-heights (if even this mode at all?)...
> 
> tegra_dc_setup_window does that check later (check the test on
> dc->soc->supports_block_linear). At the moment no error message is
> displayed though (and it seems like we are writing a stale value in
> DC_WIN_BUFFER_ADDR_MODE if the SoC doesn't support block linear and the
> tiling mode is TEGRA_BO_TILING_MODE_BLOCK?)

tegra_plane_atomic_check() has a check for this, as well as an error
message. ->atomic_check() will always run before actually setting the
mode, or applying the plane state, so it effectively guards against a
user specifying a format that the hardware doesn't support.

Thierry

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