Re: [PATCH] drm/i915: intel_pipe_config_compare: Don't compare DSI PLL regs when adjusting

[Hans de Goede <hdegoede@redhat.com>]

Hi all,

On 02-11-18 12:44, Hans de Goede wrote:
> The GOP sometimes initializes the DSI pclk at a (slightly) different freq
> then the pclk which we pick. intel_pipe_config_compare() allows for this
> by doing a fuzzy compare on the port_clock.
> 
> But the pclk difference not only results in the port_clock and
> base.adjusted_mode.crtc_clock clocks being a bit different, but also in
> us picking different dsi_pll register values matching the different pclk.
> 
> This commit makes us only do the dsi_pll register compare when the adjust
> parameter is false, so only from verify_crtc_state(), so that we correctly
> do a fast modeset at boot avoiding the screen going black for about 1 sec.
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Self-nack to this patch. This avoids the modeset on boot when
booting with fastboot=1 but then on the first commit afterwards
we get errors like these:

[    6.330864] [drm:pipe_config_err [i915]] *ERROR* mismatch in dsi_pll.ctrl (expected 0x80040100, found 0x80080100)
[    6.330967] [drm:pipe_config_err [i915]] *ERROR* mismatch in dsi_pll.div (expected 0x000001aa, found 0x0000011a)

Followed by a backtrace caused by the I915_STATE_WARN at the
end of verify_crtc_state triggering.

So I will brush of my previous patch to fix this, which reads the
pclk picked by the GOP back and uses overrides the VBT one with
that if it is close.

I believe I've a solution for not doing hw readback in intel_dsi_vbt.c,
which was the largest objection last time I posted that series.

Regards,

Hans


> ---
>   drivers/gpu/drm/i915/intel_display.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index b219d5858160..82fa85df0fba 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -11759,8 +11759,10 @@ intel_pipe_config_compare(struct drm_i915_private *dev_priv,
>   	PIPE_CONF_CHECK_X(dpll_hw_state.mg_pll_bias);
>   	PIPE_CONF_CHECK_X(dpll_hw_state.mg_pll_tdc_coldst_bias);
>   
> -	PIPE_CONF_CHECK_X(dsi_pll.ctrl);
> -	PIPE_CONF_CHECK_X(dsi_pll.div);
> +	if (!adjust) {
> +		PIPE_CONF_CHECK_X(dsi_pll.ctrl);
> +		PIPE_CONF_CHECK_X(dsi_pll.div);
> +	}
>   
>   	if (IS_G4X(dev_priv) || INTEL_GEN(dev_priv) >= 5)
>   		PIPE_CONF_CHECK_I(pipe_bpp);
> 
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