[PATCH v2 2/3] firmware: zynqmp-fpga: avoid additional buffer for size argument

[Michael Tretter]

There are two different APIs for loading an FPGA via the pmu-fw as
indicated by the ZYNQMP_PM_FEATURE_SIZE_NOT_NEEDED feature flag.
The pmu-fw expects as second argument either the size of the bitstream or a
pointer to the size of the bitstream.

The driver allocates a separate buffer for the size, which results in
the allocation of a 4k page for storing a 32 bit value.

Allocate some more memory for the bitstream and append the size of the
bitstream at the end of the bitstream to avoid the additional memory
allocation.

Add a comment to explain the surprising size of the allocation.

Signed-off-by: Michael Tretter <m.tretter at pengutronix.de>
---
 drivers/firmware/zynqmp-fpga.c | 37 +++++++++++++++-------------------
 1 file changed, 16 insertions(+), 21 deletions(-)

diff --git a/drivers/firmware/zynqmp-fpga.c b/drivers/firmware/zynqmp-fpga.c
index 736d1950fa5e..667910479aa7 100644
--- a/drivers/firmware/zynqmp-fpga.c
+++ b/drivers/firmware/zynqmp-fpga.c
@@ -197,8 +197,8 @@ static void zynqmp_fpga_show_header(const struct device_d *dev,
 static int fpgamgr_program_finish(struct firmware_handler *fh)
 {
 	struct fpgamgr *mgr = container_of(fh, struct fpgamgr, fh);
-	char *buf_aligned;
-	u32 *buf_size = NULL;
+	u32 *buf_aligned;
+	u32 buf_size;
 	u32 *body;
 	size_t body_length;
 	int header_length = 0;
@@ -234,17 +234,14 @@ static int fpgamgr_program_finish(struct firmware_handler *fh)
 		goto err_free;
 	}
 
-	if (!(mgr->features & ZYNQMP_PM_FEATURE_SIZE_NOT_NEEDED)) {
-		buf_size = dma_alloc_coherent(sizeof(*buf_size),
-		DMA_ADDRESS_BROKEN);
-		if (!buf_size) {
-			status = -ENOBUFS;
-			goto err_free;
-		}
-		*buf_size = body_length;
-	}
-
-	buf_aligned = dma_alloc_coherent(body_length, DMA_ADDRESS_BROKEN);
+	/*
+	 * The PMU FW variants without the ZYNQMP_PM_FEATURE_SIZE_NOT_NEEDED
+	 * feature expect a pointer to the bitstream size, which is stored in
+	 * memory. Allocate some extra space at the end of the buffer for the
+	 * bitstream size.
+	 */
+	buf_aligned = dma_alloc_coherent(body_length + sizeof(buf_size),
+					 DMA_ADDRESS_BROKEN);
 	if (!buf_aligned) {
 		status = -ENOBUFS;
 		goto err_free;
@@ -259,20 +256,18 @@ static int fpgamgr_program_finish(struct firmware_handler *fh)
 
 	addr = (u64)buf_aligned;
 
-	if (!(mgr->features & ZYNQMP_PM_FEATURE_SIZE_NOT_NEEDED) && buf_size) {
-		status = mgr->eemi_ops->fpga_load(addr,
-				(u32)(uintptr_t)buf_size,
-				flags);
-		dma_free_coherent(buf_size, 0, sizeof(*buf_size));
+	if (mgr->features & ZYNQMP_PM_FEATURE_SIZE_NOT_NEEDED) {
+		buf_size = body_length;
 	} else {
-		status = mgr->eemi_ops->fpga_load(addr, (u32)(body_length),
-						  flags);
+		buf_aligned[body_length / sizeof(*buf_aligned)] = body_length;
+		buf_size = addr + body_length;
 	}
 
+	status = mgr->eemi_ops->fpga_load(addr, buf_size, flags);
 	if (status < 0)
 		dev_err(&mgr->dev, "unable to load fpga\n");
 
-	dma_free_coherent(buf_aligned, 0, body_length);
+	dma_free_coherent(buf_aligned, 0, body_length + sizeof(buf_size));
 
  err_free:
 	free(mgr->buf);
-- 
2.30.2