gpu: ipu-v3: Add support for double read/write reduction

Allow to skip writing odd chroma rows by setting the RDRW bit for
4:2:0 chroma subsampled formats for any IDMAC write channel. This
also allows to skip reading odd rows for the VDIC read channel.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/gpu/ipu-v3/ipu-cpmem.c

@@ -224,6 +224,12 @@ void ipu_cpmem_set_resolution(struct ipuv3_channel *ch, int xres, int yres)
 }
 EXPORT_SYMBOL_GPL(ipu_cpmem_set_resolution);
 
+void ipu_cpmem_skip_odd_chroma_rows(struct ipuv3_channel *ch)
+{
+	ipu_ch_param_write_field(ch, IPU_FIELD_RDRW, 1);
+}
+EXPORT_SYMBOL_GPL(ipu_cpmem_skip_odd_chroma_rows);
+
 void ipu_cpmem_set_stride(struct ipuv3_channel *ch, int stride)
 {
 	ipu_ch_param_write_field(ch, IPU_FIELD_SLY, stride - 1);

include/video/imx-ipu-v3.h

@@ -250,6 +250,7 @@ struct ipu_image {
 
 void ipu_cpmem_zero(struct ipuv3_channel *ch);
 void ipu_cpmem_set_resolution(struct ipuv3_channel *ch, int xres, int yres);
+void ipu_cpmem_skip_odd_chroma_rows(struct ipuv3_channel *ch);
 void ipu_cpmem_set_stride(struct ipuv3_channel *ch, int stride);
 void ipu_cpmem_set_high_priority(struct ipuv3_channel *ch);
 void ipu_cpmem_set_buffer(struct ipuv3_channel *ch, int bufnum, dma_addr_t buf);