On Mon, Jun 05, 2017 at 12:01:45AM +0800, Icenowy Zheng wrote:
> Allwinner H3 features a TV encoder similar to the one in earlier SoCs,
> but has a internal fixed clock divider that divides the TCON1 clock
> (called TVE clock in datasheet) by 11.
> 
> Add support for it.
> 
> Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
> ---
> Changes in v2:
> - Quirk part rewritten.
> 
>  drivers/gpu/drm/sun4i/sun4i_tv.c | 35 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tv.c b/drivers/gpu/drm/sun4i/sun4i_tv.c
> index 338b9e5bb2a3..b9ff6d5ea67a 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tv.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tv.c
> @@ -13,6 +13,7 @@
>  #include <linux/clk.h>
>  #include <linux/component.h>
>  #include <linux/of_address.h>
> +#include <linux/of_device.h>
>  #include <linux/regmap.h>
>  #include <linux/reset.h>
>  
> @@ -169,14 +170,21 @@ struct tv_mode {
>  	const struct resync_parameters	*resync_params;
>  };
>  
> +struct sun4i_tv_quirks {
> +	int fixed_divider;
> +};
> +
>  struct sun4i_tv {
>  	struct drm_connector	connector;
>  	struct drm_encoder	encoder;
>  
>  	struct clk		*clk;
> +	struct clk		*mod_clk;
>  	struct regmap		*regs;
>  	struct reset_control	*reset;
>  
> +	const struct sun4i_tv_quirks *quirks;
> +
>  	struct sun4i_drv	*drv;
>  };
>  
> @@ -391,6 +399,12 @@ static void sun4i_tv_mode_set(struct drm_encoder *encoder,
>  	struct sun4i_tcon *tcon = crtc->tcon;
>  	const struct tv_mode *tv_mode = sun4i_tv_find_tv_by_mode(mode);
>  
> +	if (tv->quirks->fixed_divider) {
> +		DRM_DEBUG_DRIVER("Applying fixed divider %d on TVE clock\n",
> +				 tv->quirks->fixed_divider);
> +		mode->crtc_clock *= tv->quirks->fixed_divider;
> +	}
> +

You're not allowed to change the mode in mode_set, and you shouldn't
even change it. The output pixel clock is still 27MHz.

You should implement that using the states, as we discussed already.

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com