Re: [PATCH 1/4] drm/sun4i: dsi: Restrict DSI tcon clock divider

From: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
To: Maxime Ripard <maxime.ripard@bootlin.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Sean Paul <seanpaul@chromium.org>
Cc: bbrezillon@kernel.org, dri-devel@lists.freedesktop.org,
	Chen-Yu Tsai <wens@csie.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Jagan Teki <jagan@openedev.com>,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 1/4] drm/sun4i: dsi: Restrict DSI tcon clock divider
Date: Tue, 29 Jan 2019 16:39:53 +0100	[thread overview]
Message-ID: <5ca088ece86f8ee6033d481c7f9e86128fc5e355.camel@bootlin.com> (raw)
In-Reply-To: <92e4e5f4c58c8c1a439e93614fdcd8bad6823358.1548236066.git-series.maxime.ripard@bootlin.com>

Hi,

On Wed, 2019-01-23 at 16:54 +0100, Maxime Ripard wrote:
> The current code allows the TCON clock divider to have a range between 4
> and 127 when feeding the DSI controller.
> 
> The only display supported so far had a display clock rate that ended up
> using a divider of 4, but testing with other displays show that only 4
> seems to be functional.
> 
> This also aligns with what Allwinner is doing in their BSP, so let's just
> hardcode that we want a divider of 4 when using the DSI output.
> 
> Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>

Cheers,

Paul

> ---
>  drivers/gpu/drm/sun4i/sun4i_tcon.c     | 4 ++--
>  drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h | 2 ++
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> index 0420f5c978b9..bee73ead732a 100644
> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
> @@ -341,8 +341,8 @@ static void sun4i_tcon0_mode_set_cpu(struct sun4i_tcon *tcon,
>  	u32 block_space, start_delay;
>  	u32 tcon_div;
>  
> -	tcon->dclk_min_div = 4;
> -	tcon->dclk_max_div = 127;
> +	tcon->dclk_min_div = SUN6I_DSI_TCON_DIV;
> +	tcon->dclk_max_div = SUN6I_DSI_TCON_DIV;
>  
>  	sun4i_tcon0_mode_set_common(tcon, mode);
>  
> diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> index dbbc5b3ecbda..6d4a3c0fd9b5 100644
> --- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> +++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.h
> @@ -13,6 +13,8 @@
>  #include <drm/drm_encoder.h>
>  #include <drm/drm_mipi_dsi.h>
>  
> +#define SUN6I_DSI_TCON_DIV	4
> +
>  struct sun6i_dphy {
>  	struct clk		*bus_clk;
>  	struct clk		*mod_clk;
-- 
Paul Kocialkowski, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com


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