dmaengine: xilinx_dpdma: stop using slave_id field

The display driver wants to pass a custom flag to the DMA engine driver,
which it started doing by using the slave_id field that was traditionally
used for a different purpose.

As there is no longer a correct use for the slave_id field, it should
really be removed, and the remaining users changed over to something
different.

The new mechanism for passing nonstandard settings is using the
.peripheral_config field, so use that to pass a newly defined structure
here, making it clear that this will not work in portable drivers.

Reviewed-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Arnd Bergmann <[e-mail]>
Acked-by: Mark Brown <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/dma/xilinx/xilinx_dpdma.c

···
 #include <linux/clk.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
+#include <linux/dma/xilinx_dpdma.h>
 #include <linux/dmaengine.h>
 #include <linux/dmapool.h>
 #include <linux/interrupt.h>
···
 			       struct dma_slave_config *config)
 {
 	struct xilinx_dpdma_chan *chan = to_xilinx_chan(dchan);
+	struct xilinx_dpdma_peripheral_config *pconfig;
 	unsigned long flags;
 
 	/*
···
 	 * fixed both on the DPDMA side and on the DP controller side.
 	 */
 
-	spin_lock_irqsave(&chan->lock, flags);
-
 	/*
-	 * Abuse the slave_id to indicate that the channel is part of a video
-	 * group.
+	 * Use the peripheral_config to indicate that the channel is part
+	 * of a video group. This requires matching use of the custom
+	 * structure in each driver.
 	 */
-	if (chan->id <= ZYNQMP_DPDMA_VIDEO2)
-		chan->video_group = config->slave_id != 0;
+	pconfig = config->peripheral_config;
+	if (WARN_ON(pconfig && config->peripheral_size != sizeof(*pconfig)))
+		return -EINVAL;
 
+	spin_lock_irqsave(&chan->lock, flags);
+	if (chan->id <= ZYNQMP_DPDMA_VIDEO2 && pconfig)
+		chan->video_group = pconfig->video_group;
 	spin_unlock_irqrestore(&chan->lock, flags);
 
 	return 0;

drivers/gpu/drm/xlnx/zynqmp_disp.c

···
 
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/dma/xilinx_dpdma.h>
 #include <linux/dma-mapping.h>
 #include <linux/dmaengine.h>
 #include <linux/module.h>
···
 	zynqmp_disp_avbuf_set_format(layer->disp, layer, layer->disp_fmt);
 
 	/*
-	 * Set slave_id for each DMA channel to indicate they're part of a
+	 * Set pconfig for each DMA channel to indicate they're part of a
 	 * video group.
 	 */
 	for (i = 0; i < info->num_planes; i++) {
 		struct zynqmp_disp_layer_dma *dma = &layer->dmas[i];
+		struct xilinx_dpdma_peripheral_config pconfig = {
+			.video_group = true,
+		};
 		struct dma_slave_config config = {
 			.direction = DMA_MEM_TO_DEV,
-			.slave_id = 1,
+			.peripheral_config = &pconfig,
+			.peripheral_size = sizeof(pconfig),
 		};
 
 		dmaengine_slave_config(dma->chan, &config);

include/linux/dma/xilinx_dpdma.h

···
+// SPDX-License-Identifier: GPL-2.0
+#ifndef __LINUX_DMA_XILINX_DPDMA_H
+#define __LINUX_DMA_XILINX_DPDMA_H
+
+#include <linux/types.h>
+
+struct xilinx_dpdma_peripheral_config {
+	bool video_group;
+};
+
+#endif /* __LINUX_DMA_XILINX_DPDMA_H */