[PATCH] drm: atmel-hlcdc: Support inverting the pixel clock polarity

[Miquel Raynal]

On the SoC host controller, the pixel clock can be:
* standard: data is launched on the rising edge
* inverted: data is launched on the falling edge

Some panels may need the inverted option to be used so let's support
this DRM flag.

Signed-off-by: Miquel Raynal <miquel.ray...@bootlin.com>
---

Hello, this change was tested on a Sama5d36 based custom board with a
panel not behaving correctly if the pixel clock was not inverted.
Cheers, Miquèl

 .../gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c    | 25 +++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c 
b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
index 58184cd6ab0b..cc5cf4c2faf7 100644
--- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
+++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_crtc.c
@@ -68,7 +68,11 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc 
*c)
        struct atmel_hlcdc_crtc *crtc = drm_crtc_to_atmel_hlcdc_crtc(c);
        struct regmap *regmap = crtc->dc->hlcdc->regmap;
        struct drm_display_mode *adj = &c->state->adjusted_mode;
+       struct drm_encoder *encoder = NULL, *en_iter;
+       struct drm_connector *connector = NULL;
        struct atmel_hlcdc_crtc_state *state;
+       struct drm_device *ddev = c->dev;
+       struct drm_connector_list_iter iter;
        unsigned long mode_rate;
        struct videomode vm;
        unsigned long prate;
@@ -76,6 +80,23 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc 
*c)
        unsigned int cfg = 0;
        int div, ret;
 
+       /* get encoder from crtc */
+       drm_for_each_encoder(en_iter, ddev) {
+               if (en_iter->crtc == c) {
+                       encoder = en_iter;
+                       break;
+               }
+       }
+
+       if (encoder) {
+               /* 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);
+       }
+
        ret = clk_prepare_enable(crtc->dc->hlcdc->sys_clk);
        if (ret)
                return;
@@ -134,6 +155,10 @@ static void atmel_hlcdc_crtc_mode_set_nofb(struct drm_crtc 
*c)
 
        cfg |= ATMEL_HLCDC_CLKDIV(div);
 
+       if (connector &&
+           connector->display_info.bus_flags & 
DRM_BUS_FLAG_PIXDATA_DRIVE_NEGEDGE)
+               cfg |= ATMEL_HLCDC_CLKPOL;
+
        regmap_update_bits(regmap, ATMEL_HLCDC_CFG(0), mask, cfg);
 
        state = drm_crtc_state_to_atmel_hlcdc_crtc_state(c->state);
-- 
2.34.1