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

[Sam Ravnborg]

On Fri, Jun 09, 2023 at 04:48:43PM +0200, Miquel Raynal wrote:
> 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.raynal at bootlin.com>

Hi Miquel,

the patch is:
Reviewed-by: Sam Ravnborg <sam at ravnborg.org>

I hope someone else can pick it up and apply it to drm-misc as
my drm-misc setup is hopelessly outdated atm.

	Sam


> ---
> 
> 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