[PATCH 2/2] fpga: versal: add dma-buf programming support

[Aravind Thokala <aravind.thokala@amd.com>]

The existing .write callback allocates a DMA-coherent buffer and
copies the image into it before passing the address to firmware. With
dma-buf, the buffer is already DMA-mapped by userspace.

Add a .write_sg callback that extracts the DMA address directly from
the scatter-gather table and passes it to zynqmp_pm_load_pdi(),
avoiding the intermediate copy. Register the dma-buf interface in
probe with devres-managed cleanup.

Co-developed-by: Nava kishore Manne <nava.kishore.manne@amd.com>
Signed-off-by: Nava kishore Manne <nava.kishore.manne@amd.com>
Signed-off-by: Aravind Thokala <aravind.thokala@amd.com>
---
 drivers/fpga/versal-fpga.c | 33 ++++++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/drivers/fpga/versal-fpga.c b/drivers/fpga/versal-fpga.c
index e6189106c468..bdaa15a6c991 100644
--- a/drivers/fpga/versal-fpga.c
+++ b/drivers/fpga/versal-fpga.c
@@ -4,6 +4,7 @@
  */
 
 #include <linux/dma-mapping.h>
+#include <linux/fpga/fpga-dmabuf.h>
 #include <linux/fpga/fpga-mgr.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
@@ -37,11 +38,34 @@ static int versal_fpga_ops_write(struct fpga_manager *mgr,
 	return ret;
 }
 
+static int versal_fpga_ops_write_sg(struct fpga_manager *mgr,
+				    struct sg_table *sgt)
+{
+	dma_addr_t dma_addr;
+
+	/* zynqmp_pm_load_pdi() takes a single base address */
+	if (sgt->nents != 1) {
+		dev_err(&mgr->dev, "dma-buf has %u segments, need exactly 1\n",
+			sgt->nents);
+		return -EINVAL;
+	}
+
+	dma_addr = sg_dma_address(sgt->sgl);
+
+	return zynqmp_pm_load_pdi(PDI_SRC_DDR, dma_addr);
+}
+
 static const struct fpga_manager_ops versal_fpga_ops = {
 	.write_init = versal_fpga_ops_write_init,
 	.write = versal_fpga_ops_write,
+	.write_sg = versal_fpga_ops_write_sg,
 };
 
+static void versal_fpga_dmabuf_remove(void *data)
+{
+	fpga_dmabuf_unregister(data);
+}
+
 static int versal_fpga_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -56,7 +80,14 @@ static int versal_fpga_probe(struct platform_device *pdev)
 
 	mgr = devm_fpga_mgr_register(dev, "Xilinx Versal FPGA Manager",
 				     &versal_fpga_ops, NULL);
-	return PTR_ERR_OR_ZERO(mgr);
+	if (IS_ERR(mgr))
+		return PTR_ERR(mgr);
+
+	ret = fpga_dmabuf_register(mgr);
+	if (ret)
+		return ret;
+
+	return devm_add_action_or_reset(dev, versal_fpga_dmabuf_remove, mgr);
 }
 
 static const struct of_device_id versal_fpga_of_match[] = {
-- 
2.34.1