hantro: Add quirk for NV12/NV12_4L4 capture format

The G2 core decoder engine produces NV12_4L4 format,
which is a simple NV12 4x4 tiled format. The driver currently
hides this format by always enabling the post-processor engine,
and therefore offering NV12 directly.

This is done without using the logic in hantro_postproc.c
and therefore makes it difficult to add VP9 cleanly.

Since fixing this is not easy, add a small quirk to force
NV12 if HEVC was configured, but otherwise declare NV12_4L4
as the pixel format in imx8mq_vpu_g2_variant.dec_fmts.

This will be used by the VP9 decoder which will be added soon.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>

drivers/staging/media/hantro/hantro_v4l2.c

@@ -150,6 +150,20 @@ static int vidioc_enum_fmt(struct file *file, void *priv,
 	unsigned int num_fmts, i, j = 0;
 	bool skip_mode_none;
 
+	/*
+	 * The HEVC decoder on the G2 core needs a little quirk to offer NV12
+	 * only on the capture side. Once the post-processor logic is used,
+	 * we will be able to expose NV12_4L4 and NV12 as the other cases,
+	 * and therefore remove this quirk.
+	 */
+	if (capture && ctx->vpu_src_fmt->fourcc == V4L2_PIX_FMT_HEVC_SLICE) {
+		if (f->index == 0) {
+			f->pixelformat = V4L2_PIX_FMT_NV12;
+			return 0;
+		}
+		return -EINVAL;
+	}
+
 	/*
 	 * When dealing with an encoder:
 	 *  - on the capture side we want to filter out all MODE_NONE formats.

drivers/staging/media/hantro/imx8m_vpu_hw.c

@@ -134,7 +134,7 @@ static const struct hantro_fmt imx8m_vpu_dec_fmts[] = {
 
 static const struct hantro_fmt imx8m_vpu_g2_dec_fmts[] = {
 	{
-		.fourcc = V4L2_PIX_FMT_NV12,
+		.fourcc = V4L2_PIX_FMT_NV12_4L4,
 		.codec_mode = HANTRO_MODE_NONE,
 	},
 	{