linux-kernel - Re: [RFC 4/4] drm/sun4i: Update mixer's internal registers after initialization

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Message-ID: <2960593.5fSG56mABF@jernej-laptop>
Date:   Sun, 29 Dec 2019 10:25:12 +0100
From:   Jernej Škrabec <jernej.skrabec@...l.net>
To:     mripard@...nel.org, dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        roman.stratiienko@...ballogic.com
Cc:     Roman Stratiienko <roman.stratiienko@...ballogic.com>
Subject: Re: [RFC 4/4] drm/sun4i: Update mixer's internal registers after initialization

Hi!

Dne sobota, 28. december 2019 ob 21:28:18 CET je 
roman.stratiienko@...ballogic.com napisal(a):
> From: Roman Stratiienko <roman.stratiienko@...ballogic.com>
> 
> At system start blink of u-boot ghost framebuffer can be observed.
> Fix it.

Reviewed-by: Jernej Skrabec <jernej.skrabec@...l.net>

Please note that U-Boot to Linux handover may not be without issues. I noticed 
that in some cases, HDMI EDID readout is broken. I guess already initialized 
HDMI controller doesn't like to be reinitialized. Or it may have something to 
do with the fact that U-Boot HDMI driver sets I2C timing and Linux kernel uses 
default one.

Best regards,
Jernej

> 
> Signed-off-by: Roman Stratiienko <roman.stratiienko@...ballogic.com>
> ---
>  drivers/gpu/drm/sun4i/sun8i_mixer.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.c
> b/drivers/gpu/drm/sun4i/sun8i_mixer.c index da84fccf7784..b906b8cc464e
> 100644
> --- a/drivers/gpu/drm/sun4i/sun8i_mixer.c
> +++ b/drivers/gpu/drm/sun4i/sun8i_mixer.c
> @@ -588,6 +588,9 @@ static int sun8i_mixer_bind(struct device *dev, struct
> device *master, regmap_update_bits(mixer->engine.regs,
> SUN8I_MIXER_BLEND_PIPE_CTL(base), SUN8I_MIXER_BLEND_PIPE_CTL_EN_MSK, 0);
> 
> +	regmap_write(mixer->engine.regs, SUN8I_MIXER_GLOBAL_DBUFF,
> +		     SUN8I_MIXER_GLOBAL_DBUFF_ENABLE);
> +
>  	return 0;
> 
>  err_disable_bus_clk: