Re: [PATCH 07/11] drm/rockchip: inno_hdmi: Add basic mode validation

Maxime Ripard
2023-12-14T11:40:30Z

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On Thu, Dec 14, 2023 at 12:17:39PM +0100, Alex Bee wrote:
> Hi Maxime,
>
> Am 14.12.23 um 09:05 schrieb Maxime Ripard:
> > Hi,
> >
> > On Wed, Dec 13, 2023 at 08:51:21PM +0100, Alex Bee wrote:
> > > As per TRM this controller supports pixelclocks starting from 25 MHz. The
> > > maximum supported pixelclocks are defined by the phy configurations we
> > > have. Also it can't support modes that require doubled clocks.
> > > If there is a phy reference clock we can additionally validate against
> > > VESA DMT's recommendations.
> > > Those checks are added to the mode_valid hook of the connector and
> > > encoder's mode_fixup hook.
> > >
> > > Signed-off-by: Alex Bee <knaerzche@gmail.com>
> > > ---
> > > drivers/gpu/drm/rockchip/inno_hdmi.c | 38 ++++++++++++++++++++++++++--
> > > 1 file changed, 36 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/rockchip/inno_hdmi.c b/drivers/gpu/drm/rockchip/inno_hdmi.c
> > > index f7f0bec725f9..2f839ff31c1c 100644
> > > --- a/drivers/gpu/drm/rockchip/inno_hdmi.c
> > > +++ b/drivers/gpu/drm/rockchip/inno_hdmi.c
> > > @@ -38,6 +38,8 @@ struct inno_hdmi_variant {
> > > struct inno_hdmi_phy_config *default_phy_config;
> > > };
> > > +#define INNO_HDMI_MIN_TMDS_CLOCK 25000000U
> > > +
> > > struct hdmi_data_info {
> > > int vic;
> > > bool sink_has_audio;
> > > @@ -572,6 +574,34 @@ static int inno_hdmi_setup(struct inno_hdmi *hdmi,
> > > return 0;
> > > }
> > > +static enum drm_mode_status inno_hdmi_mode_valid(struct inno_hdmi *hdmi,
> > > + struct drm_display_mode *mode)
> > > +{
> > So, mode_valid is only called to filter out the modes retrieved by
> > get_modes, but it won't be called when userspace programs a mode. That's
> > atomic_check's job.
> >
> > So you probably want to create a shared function between atomic_check
> > and mode_valid, and call it from both places (or call mode_valid from
> > atomic_check).
>
> This actually _is_ a shared function called in
> inno_hdmi_connector_mode_valid and inno_hdmi_encoder_mode_fixup. Yes, I
> probably should use it in atomic_check _also_.

Yeah, I saw that later and forgot to rephrase.

> > > + /* No support for double-clock modes */
> > > + if (mode->flags & DRM_MODE_FLAG_DBLCLK)
> > > + return MODE_BAD;
> > > +
> > > + unsigned int mpixelclk = mode->clock * 1000;
> > Variables should be declared at the top of the function.
> Oookay ... can move them.
> > > + if (mpixelclk < INNO_HDMI_MIN_TMDS_CLOCK)
> > > + return MODE_CLOCK_LOW;
> > You probably want to check the max TMDS clock too?
>
> Not sure what you mean here. For the currently supported formats of this
> driver (rgb only) tmds clock and pixel clock are always the same.

I mean that your controller has a maximum TMDS rate it supports too
(probably something like 340MHz). You should also filter out the modes
that have a pixel clock higher than the one you can reach.

> > > @@ -602,7 +632,9 @@ static bool inno_hdmi_encoder_mode_fixup(struct drm_encoder *encoder,
> > > const struct drm_display_mode *mode,
> > > struct drm_display_mode *adj_mode)
> > > {
> > > - return true;
> > > + struct inno_hdmi *hdmi = encoder_to_inno_hdmi(encoder);
> > > +
> > > + return inno_hdmi_mode_valid(hdmi, adj_mode) == MODE_OK;
> > > }
> > Why do you call mode_valid in mode_fixup?
>
> I'm calling the shared function you asked me to introduce
> (inno_hdmi_connector_mode_valid != inno_mode_valid)

That's the mode_fixup part that I'm focused on :)

mode_fixup is the legacy function to adjust the mode to the controller
capabilities. It's optional, and you're not adjusting anything here,
just testing the same thing mode_valid did.

mode_valid has been superseeded by atomic_check anyway, so just drop
mode_valid and use your function in atomic_check like we discussed.

Maxime

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