[PATCH 3/3] media: ipu3-cio2: give each CSI-2 port its own DMA channel

[Joe Dzado <joe.dzado@icloud.com>]

Map queue N to DMA channel 2*N so several sensors can stream
concurrently. Even channels are used because the IOS interrupt bits are
shared within channel pairs, keeping every queue's interrupts distinct.
A dma_per_port module parameter (default on) restores the old
single-channel behaviour if needed.
Signed-off-by: Joe Dzado <joe.dzado@icloud.com>

---
 drivers/media/pci/intel/ipu3/ipu3-cio2.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/media/pci/intel/ipu3/ipu3-cio2.c b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
index 071c5ea4a..f92ac4010 100644
--- a/drivers/media/pci/intel/ipu3/ipu3-cio2.c
+++ b/drivers/media/pci/intel/ipu3/ipu3-cio2.c
@@ -350,10 +350,18 @@ static int cio2_csi2_calc_timing(struct cio2_device *cio2, struct cio2_queue *q,
 	return 0;
 };
 
-/* Each queue (CSI-2 port) owns one DMA channel. */
+/*
+ * Each queue (CSI-2 port) gets its own DMA channel so several sensors can stream at once.
+ * Channels 0, 2, 4, 6: IOS interrupt bits are shared by channel pairs (0/1, 2/3, ...) and
+ * IOC bits by pairs above 3, so even channels keep every queue's interrupts distinct.
+ */
+static bool dma_per_port = true;
+module_param(dma_per_port, bool, 0444);
+MODULE_PARM_DESC(dma_per_port, "Use a DMA channel per CSI-2 port (allows concurrent streams)");
+
 static unsigned int cio2_queue_dma_chan(unsigned int port)
 {
-	return CIO2_DMA_CHAN;
+	return dma_per_port ? 2 * port : CIO2_DMA_CHAN;
 }
 
 static int cio2_hw_init(struct cio2_device *cio2, struct cio2_queue *q)
-- 
2.56.0