[PATCH v4 4/4] drm/rockchip: dw_hdmi: discard modes with unachievable pixelclocks

[Sascha Hauer]

On Tue, Feb 07, 2023 at 11:01:26AM +0000, Jonas Karlman wrote:
> Hi Sascha,
> 
> On 2023-02-07 09:44, Sascha Hauer wrote:
> > The Rockchip PLL drivers are currently table based and support only
> > the most common pixelclocks. Discard all modes we cannot achieve
> > at all. Normally the desired pixelclocks have an exact match in the
> > PLL driver, nevertheless allow for a 0.1% error just in case.
> > 
> > Tested-by: Nicolas Frattaroli <frattaroli.nicolas at gmail.com>
> > Tested-by: Michael Riesch <michael.riesch at wolfvision.net>
> > Tested-by: Dan Johansen <strit at manjaro.org>
> > Link: https://lore.kernel.org/r/20230118132213.2911418-4-s.hauer@pengutronix.de
> > Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
> > ---
> >  drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
> > index feba6b9becd6c..725952811752b 100644
> > --- a/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
> > +++ b/drivers/gpu/drm/rockchip/dw_hdmi-rockchip.c
> > @@ -256,10 +256,14 @@ dw_hdmi_rockchip_mode_valid(struct dw_hdmi *dw_hdmi, void *data,
> >  {
> >  	struct rockchip_hdmi *hdmi = data;
> >  	const struct dw_hdmi_mpll_config *mpll_cfg = rockchip_mpll_cfg;
> > -	int pclk = mode->clock * 1000;
> > +	int rpclk, pclk = mode->clock * 1000;
> >  	bool exact_match = hdmi->plat_data->phy_force_vendor;
> >  	int i;
> >  
> > +	rpclk = clk_round_rate(hdmi->ref_clk, pclk);
> > +	if (abs(rpclk - pclk) > pclk / 1000)
> > +		return MODE_NOCLOCK;
> 
> The ref_clk is optional and rk3228/rk3328 dts do not supply a ref or vpll clock.

That's a bit unfortunate as we can't do this check then on these SoCs.

The clock is likely actually there in the system and maybe even in the
clock driver, just not wired up to the HDMI. I don't know which one it
is though, so I am afraid there's not much I can do about it other than
just skipping the check when the clock is not there.

Sascha

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