Hi Marek.
On Sat, Oct 03, 2020 at 01:07:26AM +0200, Marek Vasut wrote:
> The drm_display_mode_to_videomode() does not populate DISPLAY_FLAGS_DE_LOW
> or DISPLAY_FLAGS_PIXDATA_NEGEDGE flags in struct videomode.
So after reading this paragrahp I assumed this patch would fix this, alas
there is no changes to drm_modes.c.
Rather than introducing hacks could we try to fix the root cause here?
Root cause - as you point out is that there is missing some flags in
the conversion.
Another point is that the stm driver could drop the use of
drm_display_mode_to_videomode() - all the information is available in drm_display_mode
and using drm_display_mode_to_videomode() does not help much.
If the point is to have easier access to hsync and friendns maybe we
should have a few helpers operating direct on display_mode and not this
conversion to video_mode which is something that belongs to fbdev and
should IMO not be used inside a drm driver.
Sam
> Therefore, no
> matter what polarity the next bridge or display might require, these flags
> are never set, and thus the LTDC GCR_DEPOL and GCR_PCPOL bits are never set,
> and the LTDC behaves as if both DISPLAY_FLAGS_PIXDATA_POSEDGE and
> DISPLAY_FLAGS_DE_HIGH were always set.
>
> The fix for this problem is taken almost verbatim from MXSFB driver. In
> case there is a bridge attached to the LTDC, the bridge might have extra
> polarity requirements, so extract bus_flags from the bridge and use them
> for LTDC configuration. Otherwise, extract bus_flags from the connector,
> which is the display.
>
> Fixes: b759012c5fa7 ("drm/stm: Add STM32 LTDC driver")
> Signed-off-by: Marek Vasut <marex@xxxxxxx>
> Cc: Alexandre Torgue <alexandre.torgue@xxxxxx>
> Cc: Antonio Borneo <antonio.borneo@xxxxxx>
> Cc: Benjamin Gaignard <benjamin.gaignard@xxxxxx>
> Cc: Maxime Coquelin <mcoquelin.stm32@xxxxxxxxx>
> Cc: Philippe Cornu <philippe.cornu@xxxxxx>
> Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
> Cc: Vincent Abriou <vincent.abriou@xxxxxx>
> Cc: Yannick Fertre <yannick.fertre@xxxxxx>
> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> Cc: linux-stm32@xxxxxxxxxxxxxxxxxxxxxxxxxxxx
> To: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> ---
> drivers/gpu/drm/stm/ltdc.c | 22 ++++++++++++++++++++--
> drivers/gpu/drm/stm/ltdc.h | 2 ++
> 2 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 07c73079293c..a282a1553497 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -546,11 +546,17 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
> struct drm_device *ddev = crtc->dev;
> struct drm_display_mode *mode = &crtc->state->adjusted_mode;
> struct videomode vm;
> + u32 bus_flags = 0;
> u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
> u32 total_width, total_height;
> u32 val;
> int ret;
>
> + if (ldev->bridge)
> + bus_flags = ldev->bridge->timings->input_bus_flags;
> + else if (ldev->connector)
> + bus_flags = ldev->connector->display_info.bus_flags;
> +
> if (!pm_runtime_active(ddev->dev)) {
> ret = pm_runtime_get_sync(ddev->dev);
> if (ret) {
> @@ -586,10 +592,10 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
> if (vm.flags & DISPLAY_FLAGS_VSYNC_HIGH)
> val |= GCR_VSPOL;
>
> - if (vm.flags & DISPLAY_FLAGS_DE_LOW)
> + if (bus_flags & DRM_BUS_FLAG_DE_LOW)
> val |= GCR_DEPOL;
>
> - if (vm.flags & DISPLAY_FLAGS_PIXDATA_NEGEDGE)
> + if (bus_flags & DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
> val |= GCR_PCPOL;
>
> reg_update_bits(ldev->regs, LTDC_GCR,
> @@ -1098,6 +1104,8 @@ static const struct drm_encoder_helper_funcs ltdc_encoder_helper_funcs = {
>
> static int ltdc_encoder_init(struct drm_device *ddev, struct drm_bridge *bridge)
> {
> + struct ltdc_device *ldev = ddev->dev_private;
> + struct drm_connector_list_iter iter;
> struct drm_encoder *encoder;
> int ret;
>
> @@ -1119,6 +1127,16 @@ static int ltdc_encoder_init(struct drm_device *ddev, struct drm_bridge *bridge)
> return -EINVAL;
> }
>
> + ldev->bridge = bridge;
> +
> + /*
> + * Get hold of the connector. This is a bit of a hack, until the bridge
> + * API gives us bus flags and formats.
> + */
> + drm_connector_list_iter_begin(ddev, &iter);
> + ldev->connector = drm_connector_list_iter_next(&iter);
> + drm_connector_list_iter_end(&iter);
> +
> DRM_DEBUG_DRIVER("Bridge encoder:%d created\n", encoder->base.id);
>
> return 0;
> diff --git a/drivers/gpu/drm/stm/ltdc.h b/drivers/gpu/drm/stm/ltdc.h
> index f153b908c70e..d0d2c81de29a 100644
> --- a/drivers/gpu/drm/stm/ltdc.h
> +++ b/drivers/gpu/drm/stm/ltdc.h
> @@ -38,6 +38,8 @@ struct ltdc_device {
> u32 irq_status;
> struct fps_info plane_fpsi[LTDC_MAX_LAYER];
> struct drm_atomic_state *suspend_state;
> + struct drm_bridge *bridge;
> + struct drm_connector *connector;
> };
>
> int ltdc_load(struct drm_device *ddev);
> --
> 2.28.0
>
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