linux-kernel - [PATCH] media: imx: prpencvf: enable double write reduction

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Date:   Sat, 22 Jul 2017 14:21:41 -0700
From:   Steve Longerbeam <slongerbeam@...il.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-media@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: [PATCH] media: imx: prpencvf: enable double write reduction

For the write channels with 4:2:0 subsampled YUV formats, avoid chroma
overdraw by only writing chroma for even lines. Reduces necessary write
memory bandwidth by at least 25% (more with rotation enabled).

Signed-off-by: Steve Longerbeam <steve_longerbeam@...tor.com>
---
 drivers/staging/media/imx/imx-ic-prpencvf.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/staging/media/imx/imx-ic-prpencvf.c b/drivers/staging/media/imx/imx-ic-prpencvf.c
index ed363fe..42c5045 100644
--- a/drivers/staging/media/imx/imx-ic-prpencvf.c
+++ b/drivers/staging/media/imx/imx-ic-prpencvf.c
@@ -374,6 +374,17 @@ static int prp_setup_channel(struct prp_priv *priv,
 	image.phys0 = addr0;
 	image.phys1 = addr1;
 
+	if (channel == priv->out_ch || channel == priv->rot_out_ch) {
+		switch (image.pix.pixelformat) {
+		case V4L2_PIX_FMT_YUV420:
+		case V4L2_PIX_FMT_YVU420:
+		case V4L2_PIX_FMT_NV12:
+			/* Skip writing U and V components to odd rows */
+			ipu_cpmem_skip_odd_chroma_rows(channel);
+			break;
+		}
+	}
+
 	ret = ipu_cpmem_set_image(channel, &image);
 	if (ret)
 		return ret;
-- 
2.7.4