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

icenowy
2017-06-11T06:43:47Z

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.)

>
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