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

Maxime Ripard
2017-06-23T14:44:11Z

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On Tue, Jun 13, 2017 at 05:51:42PM +0800, Icenowy Zheng wrote:
>
>
> 于 2017年6月13日 GMT+08:00 下午3:44:32, Maxime Ripard <maxime.ripard@free-electrons.com> 写到:
> >On Sun, Jun 11, 2017 at 02:43:42PM +0800, icenowy@aosc.io wrote:
> >> 在 2017-06-07 17:38，Maxime Ripard 写道：
> >> > 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.
> >>
> >> 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.)
> >
> >No, it's not. The pixel clock in the mode is the pixel clock output
> >physically by the connector. You want to use it for an intermediate
> >clock in your pipeline.
> >
> >This is not the same clock, and not the same frequency.
>
> So should a multiplier parameter be passed via
> tcon1_mode_set function?

No, and I've explained a couple of times already what you needed to
do. Please read again the previous messages.

Maxime

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

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