Re: [PATCH v2 07/11] drm: sun4i: add support for the TV encoder in H3 SoC

[icenowy]

å 2017-06-07 17:38ïMaxime Ripard åéï
> 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@xxxxxxx>
> > ---
> > 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.

After reading the comments at include/drm/drm_modeset_helper_vtables.h,
I think the atomic_check function is allowed to directly change
the adjust_mode of crtc_state.

And according to other comments at include/drm/drm_modes.h, the
crtc_clock in adjust_mode should be the clock to be really feed
to the hardware.

So I think I can just change this in atomic_check.

However, the mode_set function of sun4i_tv seems to be not
regarding adjusted_mode and still use original mode.

So my current design is:
- Multiply adjusted_mode in atomic_check.
- Feed adjust_mode to TCON code in mode_set function.

Is this proper?

(From my own understanding to the comments I think so.)

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