Re: [PATCH V2 2/2] drm/bridge: chrontel-ch7033: Add byteswap order setting

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Chris,

Thank you for the patch.

On Fri, Sep 02, 2022 at 10:39:06AM -0500, Chris Morgan wrote:
> From: Chris Morgan <macromorgan@hotmail.com>
> 
> Add the option to set the byteswap order in the devicetree. For the
> official HDMI DIP for the NTC CHIP the byteswap order needs to be
> RGB, however the driver sets it as BGR. With this patch the driver
> will remain at BGR unless manually specified via devicetree.
> 
> Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
> Reviewed-by: Robert Foss <robert.foss@linaro.org>
> ---
>  drivers/gpu/drm/bridge/chrontel-ch7033.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/chrontel-ch7033.c b/drivers/gpu/drm/bridge/chrontel-ch7033.c
> index ba060277c3fd..c5719908ce2d 100644
> --- a/drivers/gpu/drm/bridge/chrontel-ch7033.c
> +++ b/drivers/gpu/drm/bridge/chrontel-ch7033.c
> @@ -68,6 +68,7 @@ enum {
>  	BYTE_SWAP_GBR	= 3,
>  	BYTE_SWAP_BRG	= 4,
>  	BYTE_SWAP_BGR	= 5,
> +	BYTE_SWAP_MAX	= 6,
>  };
>  
>  /* Page 0, Register 0x19 */
> @@ -355,6 +356,8 @@ static void ch7033_bridge_mode_set(struct drm_bridge *bridge,
>  	int hsynclen = mode->hsync_end - mode->hsync_start;
>  	int vbporch = mode->vsync_start - mode->vdisplay;
>  	int vsynclen = mode->vsync_end - mode->vsync_start;
> +	u8 byte_swap;
> +	int ret;
>  
>  	/*
>  	 * Page 4
> @@ -398,8 +401,16 @@ static void ch7033_bridge_mode_set(struct drm_bridge *bridge,
>  	regmap_write(priv->regmap, 0x15, vbporch);
>  	regmap_write(priv->regmap, 0x16, vsynclen);
>  
> -	/* Input color swap. */
> -	regmap_update_bits(priv->regmap, 0x18, SWAP, BYTE_SWAP_BGR);
> +	/* Input color swap. Byte order is optional and will default to
> +	 * BYTE_SWAP_BGR to preserve backwards compatibility with existing
> +	 * driver.
> +	 */
> +	ret = of_property_read_u8(priv->bridge.of_node, "chrontel,byteswap",
> +				  &byte_swap);

That's quite inefficient, please parse the device tree at probe time,
and cache the value.

> +	if (!ret && byte_swap < BYTE_SWAP_MAX)
> +		regmap_update_bits(priv->regmap, 0x18, SWAP, byte_swap);
> +	else
> +		regmap_update_bits(priv->regmap, 0x18, SWAP, BYTE_SWAP_BGR);
>  
>  	/* Input clock and sync polarity. */
>  	regmap_update_bits(priv->regmap, 0x19, 0x1, mode->clock >> 16);

-- 
Regards,

Laurent Pinchart