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Date:   Sun, 31 Jul 2022 23:55:40 +0300
From:   Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To:     Paul Elder <paul.elder@ideasonboard.com>
Cc:     linux-media@vger.kernel.org, Dafna Hirschfeld <dafna@fastmail.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Heiko Stuebner <heiko@sntech.de>,
        linux-rockchip@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] media: rkisp1: Add UYVY as an output format
Message-ID: <YubsTAmY/B9F1Dhy@pendragon.ideasonboard.com>
References: <20220728130505.2077842-1-paul.elder@ideasonboard.com>
 <20220728130505.2077842-3-paul.elder@ideasonboard.com>
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In-Reply-To: <20220728130505.2077842-3-paul.elder@ideasonboard.com>
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Hi Paul,

Thank you for the patch.

On Thu, Jul 28, 2022 at 10:05:05PM +0900, Paul Elder wrote:
> Add support for UYVY as an output format. The uv_swap bit in the
> MI_XTD_FORMAT_CTRL register that is used for the NV formats does not
> work for packed YUV formats. Thus, UYVY support is implemented via
> byte-swapping. This method clearly does not work for implementing
> support for YVYU and VYUY.
> 
> Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
> 
> ---
> Changes in v2:
> - s@uv@U/V@
> - SP has been kept (so, uh, *not* changed in v2)
> 
> UYVY for the self path has not been tested because no device supports
> it. The rk3399 has a self path, but does not have the
> MI_OUTPUT_ALIGN_FORMAT register and thus does not support UYVY. The
> i.MX8MP does support UYVY, but does not have a self path.
> ---
>  .../platform/rockchip/rkisp1/rkisp1-capture.c | 41 +++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c b/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
> index 9fb4879e65fa..0d5e3373e1f5 100644
> --- a/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
> +++ b/drivers/media/platform/rockchip/rkisp1/rkisp1-capture.c
> @@ -97,6 +97,12 @@ static const struct rkisp1_capture_fmt_cfg rkisp1_mp_fmts[] = {
>  		.uv_swap = 0,
>  		.write_format = RKISP1_MI_CTRL_MP_WRITE_YUVINT,
>  		.mbus = MEDIA_BUS_FMT_YUYV8_2X8,
> +	}, {
> +		.fourcc = V4L2_PIX_FMT_UYVY,
> +		.uv_swap = 0,
> +		.yc_swap = 1,
> +		.write_format = RKISP1_MI_CTRL_MP_WRITE_YUVINT,
> +		.mbus = MEDIA_BUS_FMT_YUYV8_2X8,
>  	}, {
>  		.fourcc = V4L2_PIX_FMT_YUV422P,
>  		.uv_swap = 0,
> @@ -231,6 +237,13 @@ static const struct rkisp1_capture_fmt_cfg rkisp1_sp_fmts[] = {
>  		.write_format = RKISP1_MI_CTRL_SP_WRITE_INT,
>  		.output_format = RKISP1_MI_CTRL_SP_OUTPUT_YUV422,
>  		.mbus = MEDIA_BUS_FMT_YUYV8_2X8,
> +	}, {
> +		.fourcc = V4L2_PIX_FMT_UYVY,
> +		.uv_swap = 0,
> +		.yc_swap = 1,
> +		.write_format = RKISP1_MI_CTRL_SP_WRITE_INT,
> +		.output_format = RKISP1_MI_CTRL_SP_OUTPUT_YUV422,
> +		.mbus = MEDIA_BUS_FMT_YUYV8_2X8,
>  	}, {
>  		.fourcc = V4L2_PIX_FMT_YUV422P,
>  		.uv_swap = 0,
> @@ -464,6 +477,20 @@ static void rkisp1_mp_config(struct rkisp1_capture *cap)
>  		rkisp1_write(rkisp1, RKISP1_CIF_MI_XTD_FORMAT_CTRL, reg);
>  	}
>  
> +	/*
> +	 * U/V swapping with the MI_XTD_FORMAT_CTRL register only works for
> +	 * NV12/NV21 and NV16/NV61, so instead use byte swap to support UYVY.
> +	 * YVYU and VYUY cannot be supported with this method.
> +	 */
> +	if (rkisp1->info->features & RKISP1_FEATURE_MI_OUTPUT_ALIGN) {
> +		reg = rkisp1_read(rkisp1, RKISP1_CIF_MI_OUTPUT_ALIGN_FORMAT);
> +		if (cap->pix.cfg->yc_swap)
> +			reg |= RKISP1_CIF_OUTPUT_ALIGN_FORMAT_MP_BYTE_SWAP_BYTES;
> +		else
> +			reg &= ~RKISP1_CIF_OUTPUT_ALIGN_FORMAT_MP_BYTE_SWAP_BYTES;
> +		rkisp1_write(rkisp1, RKISP1_CIF_MI_OUTPUT_ALIGN_FORMAT, reg);
> +	}

I dislike read-modify-write sequences when the register isn't fully
initialized to a known value somewhere. This issue applies to other
registers too, so we could fix it globally on top.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> +
>  	rkisp1_mi_config_ctrl(cap);
>  
>  	reg = rkisp1_read(rkisp1, RKISP1_CIF_MI_CTRL);
> @@ -505,6 +532,20 @@ static void rkisp1_sp_config(struct rkisp1_capture *cap)
>  		rkisp1_write(rkisp1, RKISP1_CIF_MI_XTD_FORMAT_CTRL, reg);
>  	}
>  
> +	/*
> +	 * U/V swapping with the MI_XTD_FORMAT_CTRL register only works for
> +	 * NV12/NV21 and NV16/NV61, so instead use byte swap to support UYVY.
> +	 * YVYU and VYUY cannot be supported with this method.
> +	 */
> +	if (rkisp1->info->features & RKISP1_FEATURE_MI_OUTPUT_ALIGN) {
> +		reg = rkisp1_read(rkisp1, RKISP1_CIF_MI_OUTPUT_ALIGN_FORMAT);
> +		if (cap->pix.cfg->yc_swap)
> +			reg |= RKISP1_CIF_OUTPUT_ALIGN_FORMAT_SP_BYTE_SWAP_BYTES;
> +		else
> +			reg &= ~RKISP1_CIF_OUTPUT_ALIGN_FORMAT_SP_BYTE_SWAP_BYTES;
> +		rkisp1_write(rkisp1, RKISP1_CIF_MI_OUTPUT_ALIGN_FORMAT, reg);
> +	}
> +
>  	rkisp1_mi_config_ctrl(cap);
>  
>  	mi_ctrl = rkisp1_read(rkisp1, RKISP1_CIF_MI_CTRL);

-- 
Regards,

Laurent Pinchart