[PATCH v8 07/14] drm: bridge: samsung-dsim: Add atomic_check

[Jagan Teki <jagan@amarulasolutions.com>]

Look like an explicit fixing up of mode_flags is required for DSIM IP
present in i.MX8M Mini/Nano SoCs.

At least the LCDIF + DSIM needs active low sync polarities in order
to correlate the correct sync flags of the surrounding components in
the chain to make sure the whole pipeline can work properly.

On the other hand the i.MX 8M Mini Applications Processor Reference Manual,
Rev. 3, 11/2020 says.
"13.6.3.5.2 RGB interface
 Vsync, Hsync, and VDEN are active high signals."

i.MX 8M Mini Applications Processor Reference Manual Rev. 3, 11/2020
3.6.3.5.2 RGB interface
i.MX 8M Nano Applications Processor Reference Manual Rev. 2, 07/2022
13.6.2.7.2 RGB interface
both claim "Vsync, Hsync, and VDEN are active high signals.", the
LCDIF must generate inverted HS/VS/DE signals, i.e. active LOW.

No clear evidence about whether it can be documentation issues or
something, so added a comment FIXME for this and updated the active low
sync polarities using SAMSUNG_DSIM_TYPE_IMX8MM hw_type.

v8:
* update the comments about sync signals polarities
* added clear commit message by including i.MX8M Nano details

v7:
* fix the hw_type checking logic

v6:
* none

v5:
* rebase based new bridge changes [mszyprow]
* remove DSIM_QUIRK_FIXUP_SYNC_POL
* add hw_type check for sync polarities change.

v4:
* none

v3:
* add DSIM_QUIRK_FIXUP_SYNC_POL to handle mode_flasg fixup

v2:
* none

v1:
* fix mode flags in atomic_check instead of mode_fixup

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index ec7e01ae02ea..3c0a8580508b 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -1315,6 +1315,32 @@ static void samsung_dsim_atomic_post_disable(struct drm_bridge *bridge,
 	pm_runtime_put_sync(dsi->dev);
 }
 
+static int samsung_dsim_atomic_check(struct drm_bridge *bridge,
+				     struct drm_bridge_state *bridge_state,
+				     struct drm_crtc_state *crtc_state,
+				     struct drm_connector_state *conn_state)
+{
+	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
+	struct drm_display_mode *adjusted_mode = &crtc_state->adjusted_mode;
+
+	/*
+	 * The i.MX8M Mini/Nano glue logic between LCDIF and DSIM
+	 * inverts HS/VS/DE sync signals polarity, therefore, while
+	 * i.MX 8M Mini Applications Processor Reference Manual Rev. 3, 11/2020
+	 * 13.6.3.5.2 RGB interface
+	 * i.MX 8M Nano Applications Processor Reference Manual Rev. 2, 07/2022
+	 * 13.6.2.7.2 RGB interface
+	 * both claim "Vsync, Hsync, and VDEN are active high signals.", the
+	 * LCDIF must generate inverted HS/VS/DE signals, i.e. active LOW.
+	 */
+	if (dsi->plat_data->hw_type == SAMSUNG_DSIM_TYPE_IMX8MM) {
+		adjusted_mode->flags |= (DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC);
+		adjusted_mode->flags &= ~(DRM_MODE_FLAG_PHSYNC | DRM_MODE_FLAG_PVSYNC);
+	}
+
+	return 0;
+}
+
 static void samsung_dsim_mode_set(struct drm_bridge *bridge,
 				  const struct drm_display_mode *mode,
 				  const struct drm_display_mode *adjusted_mode)
@@ -1353,6 +1379,7 @@ static const struct drm_bridge_funcs samsung_dsim_bridge_funcs = {
 	.atomic_duplicate_state		= drm_atomic_helper_bridge_duplicate_state,
 	.atomic_destroy_state		= drm_atomic_helper_bridge_destroy_state,
 	.atomic_reset			= drm_atomic_helper_bridge_reset,
+	.atomic_check			= samsung_dsim_atomic_check,
 	.atomic_pre_enable		= samsung_dsim_atomic_pre_enable,
 	.atomic_enable			= samsung_dsim_atomic_enable,
 	.atomic_disable			= samsung_dsim_atomic_disable,
-- 
2.25.1