On Tue, Apr 24, 2018 at 9:48 AM, Maxime Ripard
<maxime.ripard@xxxxxxxxxxx> wrote:
> The vc4 HVS uses an internal RGB888 representation of the frames, and will
> by default expand formats using a lower depth using zeros.
>
> This causes an issue when we try to use other compositing software such as
> pixman that seems to be filling the missing bits using the format least
> significant bit value. As such, this prevents us from checking the display
> output in a reliable way.
>
> To prevent this, force the same behaviour so that we can do such things.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxx>
> ---
> drivers/gpu/drm/vc4/vc4_plane.c | 1 +
> drivers/gpu/drm/vc4/vc4_regs.h | 8 ++++++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
> index ce39390be389..8dd33c6e9fd8 100644
> --- a/drivers/gpu/drm/vc4/vc4_plane.c
> +++ b/drivers/gpu/drm/vc4/vc4_plane.c
> @@ -542,6 +542,7 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
> /* Control word */
> vc4_dlist_write(vc4_state,
> SCALER_CTL0_VALID |
> + VC4_SET_FIELD(SCALER_CTL0_EXPAND_LSB, SCALER_CTL0_EXPAND) |
> (format->pixel_order << SCALER_CTL0_ORDER_SHIFT) |
> (format->hvs << SCALER_CTL0_PIXEL_FORMAT_SHIFT) |
> VC4_SET_FIELD(tiling, SCALER_CTL0_TILING) |
> diff --git a/drivers/gpu/drm/vc4/vc4_regs.h b/drivers/gpu/drm/vc4/vc4_regs.h
> index a141496104a6..7c28e6207ec2 100644
> --- a/drivers/gpu/drm/vc4/vc4_regs.h
> +++ b/drivers/gpu/drm/vc4/vc4_regs.h
> @@ -806,12 +806,20 @@ enum hvs_pixel_format {
> #define SCALER_CTL0_ORDER_MASK VC4_MASK(14, 13)
> #define SCALER_CTL0_ORDER_SHIFT 13
>
> +#define SCALER_CTL0_EXPAND_MASK VC4_MASK(12, 11)
> +#define SCALER_CTL0_EXPAND_SHIFT 11
> +
> #define SCALER_CTL0_SCL1_MASK VC4_MASK(10, 8)
> #define SCALER_CTL0_SCL1_SHIFT 8
>
> #define SCALER_CTL0_SCL0_MASK VC4_MASK(7, 5)
> #define SCALER_CTL0_SCL0_SHIFT 5
>
> +#define SCALER_CTL0_EXPAND_ZERO 0
> +#define SCALER_CTL0_EXPAND_LSB 1
> +#define SCALER_CTL0_EXPAND_MSB 2
> +#define SCALER_CTL0_EXPAND_REPEAT 3
Just a heads up, those defines have recently landed in drm-misc, with
slightly different naming: SCALER_CTL0_RGBA_EXPAND_*
Thanks,
Stefan
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