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

Icenowy Zheng
2017-06-13T09:53:00Z

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?

>
>Maxime