fpga zynq: Check the bitstream for validity

There is no sense in sending a bitstream we know will not work, and
with the variety of options for bitstream generation in Xilinx tools
it is not terribly clear what the correct input should be.

This is particularly important for Zynq since auto-correction was
removed from the driver and the Zynq hardware only accepts a bitstream
format that is different from what the Xilinx tools typically produce.

Worse, the hardware provides no indication why the bitstream fails,
it simply times out if the input is wrong.

The best option here is to have the kernel print a message informing
the user they are using a malformed bistream and programming failure
isn't for any of the myriad of other reasons.
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Acked-by: Moritz Fischer <moritz.fischer@ettus.com>
Acked-by: Alan Tull <atull@opensource.altera.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/fpga/zynq-fpga.c

@@ -161,6 +161,19 @@ static irqreturn_t zynq_fpga_isr(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+/* Sanity check the proposed bitstream. It must start with the sync word in
+ * the correct byte order, and be dword aligned. The input is a Xilinx .bin
+ * file with every 32 bit quantity swapped.
+ */
+static bool zynq_fpga_has_sync(const u8 *buf, size_t count)
+{
+	for (; count >= 4; buf += 4, count -= 4)
+		if (buf[0] == 0x66 && buf[1] == 0x55 && buf[2] == 0x99 &&
+		    buf[3] == 0xaa)
+			return true;
+	return false;
+}
+
 static int zynq_fpga_ops_write_init(struct fpga_manager *mgr,
 				    struct fpga_image_info *info,
 				    const char *buf, size_t count)
@@ -177,6 +190,13 @@ static int zynq_fpga_ops_write_init(struct fpga_manager *mgr,
 
 	/* don't globally reset PL if we're doing partial reconfig */
 	if (!(info->flags & FPGA_MGR_PARTIAL_RECONFIG)) {
+		if (!zynq_fpga_has_sync(buf, count)) {
+			dev_err(&mgr->dev,
+				"Invalid bitstream, could not find a sync word. Bitstream must be a byte swapped .bin file\n");
+			err = -EINVAL;
+			goto out_err;
+		}
+
 		/* assert AXI interface resets */
 		regmap_write(priv->slcr, SLCR_FPGA_RST_CTRL_OFFSET,
 			     FPGA_RST_ALL_MASK);
@@ -410,6 +430,7 @@ static enum fpga_mgr_states zynq_fpga_ops_state(struct fpga_manager *mgr)
 }
 
 static const struct fpga_manager_ops zynq_fpga_ops = {
+	.initial_header_size = 128,
 	.state = zynq_fpga_ops_state,
 	.write_init = zynq_fpga_ops_write_init,
 	.write = zynq_fpga_ops_write,