drm/stm: Fix bus_flags handling

The drm_display_mode_to_videomode() does not populate DISPLAY_FLAGS_DE_LOW
or DISPLAY_FLAGS_PIXDATA_NEGEDGE flags in struct videomode. 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@denx.de>
Signed-off-by: Yannick Fertre <yannick.fertre@st.com>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Antonio Borneo <antonio.borneo@st.com>
Cc: Benjamin Gaignard <benjamin.gaignard@st.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Philippe Cornu <philippe.cornu@st.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Vincent Abriou <vincent.abriou@st.com>
Cc: Yannick Fertre <yannick.fertre@st.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-stm32@st-md-mailman.stormreply.com
To: dri-devel@lists.freedesktop.org
Tested-by: Yannick Fertre <yannick.fertre@foss.st.com>
Signed-off-by: Philippe Cornu <philippe.cornu@foss.st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210127110756.125570-1-marex@denx.de

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 7812094..6f3b523 100644 (file)
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -525,13 +525,42 @@ static void ltdc_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
        struct ltdc_device *ldev = crtc_to_ltdc(crtc);
        struct drm_device *ddev = crtc->dev;
+       struct drm_connector_list_iter iter;
+       struct drm_connector *connector = NULL;
+       struct drm_encoder *encoder = NULL;
+       struct drm_bridge *bridge = NULL;
        struct drm_display_mode *mode = &crtc->state->adjusted_mode;
        struct videomode vm;
        u32 hsync, vsync, accum_hbp, accum_vbp, accum_act_w, accum_act_h;
        u32 total_width, total_height;
+       u32 bus_flags = 0;
        u32 val;
        int ret;
 
+       /* get encoder from crtc */
+       drm_for_each_encoder(encoder, ddev)
+               if (encoder->crtc == crtc)
+                       break;
+
+       if (encoder) {
+               /* get bridge from encoder */
+               list_for_each_entry(bridge, &encoder->bridge_chain, chain_node)
+                       if (bridge->encoder == encoder)
+                               break;
+
+               /* Get the connector from encoder */
+               drm_connector_list_iter_begin(ddev, &iter);
+               drm_for_each_connector_iter(connector, &iter)
+                       if (connector->encoder == encoder)
+                               break;
+               drm_connector_list_iter_end(&iter);
+       }
+
+       if (bridge && bridge->timings)
+               bus_flags = bridge->timings->input_bus_flags;
+       else if (connector)
+               bus_flags = connector->display_info.bus_flags;
+
        if (!pm_runtime_active(ddev->dev)) {
                ret = pm_runtime_get_sync(ddev->dev);
                if (ret) {
@@ -567,10 +596,10 @@ 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,