David Hendricks has uploaded this change for review.

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dediprog: Break apart large (>=32MiB) transfers

The 2-byte length defined in the command spec appears to be 1-based,
that is to say that we can transfer 65536 - 1 data packets of 512
bytes in one bulk read request, just shy of 32MiB.

Attempting to read >=32MiB at once will result in bulk read failure
(with "SPI bulk read failed!" messages). This patch breaks the transfer
at 32MiB - 512 bytes to avoid that.

Tested using an SF600 (FW v7.2.21), IS25LP256D, W25Q256JV, and
MX25L25735.

Change-Id: Ia42253137719607c1525581049239cc9e88880a3
Signed-off-by: David Hendricks <david.hendricks@gmail.com>
---
M dediprog.c
1 file changed, 23 insertions(+), 9 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/20/30520/1

diff --git a/dediprog.c b/dediprog.c
index 7738459..2a190d2 100644
--- a/dediprog.c
+++ b/dediprog.c
@@ -557,6 +557,7 @@
 	const unsigned int chunksize = 0x200;
 	unsigned int residue = start % chunksize ? min(len, chunksize - start % chunksize) : 0;
 	unsigned int bulklen;
+	uint32_t max_xfer = 0x2000000 - chunksize;
 
 	dediprog_set_leds(LED_BUSY);
 
@@ -570,18 +571,31 @@
 
 	/* Round down. */
 	bulklen = (len - residue) / chunksize * chunksize;
-	ret = dediprog_spi_bulk_read(flash, buf + residue, start + residue, bulklen);
-	if (ret)
-		goto err;
 
-	len -= residue + bulklen;
-	if (len != 0) {
-		msg_pdbg("Slow read for partial block from 0x%x, length 0x%x\n",
-			 start, len);
-		ret = spi_read_chunked(flash, buf + residue + bulklen,
-				       start + residue + bulklen, len, 16);
+	/* Break apart large transfers (32MB - chunksize) to avoid "SPI bulk
+	 * read failed!" errors */
+	while (bulklen > 0) {
+		unsigned int xfer_size = min(bulklen, max_xfer);
+		ret = dediprog_spi_bulk_read(flash, buf + residue, start + residue, xfer_size);
 		if (ret)
 			goto err;
+
+		len -= residue + xfer_size;
+		if (len == chunksize) {
+			ret = dediprog_spi_bulk_read(flash,
+					buf + residue + xfer_size,
+					start + residue + xfer_size, chunksize);
+			len -= chunksize;
+			bulklen -= chunksize;
+		} else if (len != 0) {
+			msg_pdbg("Slow read for partial block from 0x%x, length 0x%x\n",
+				 start, len);
+			ret = spi_read_chunked(flash, buf + residue + xfer_size,
+				       start + residue + xfer_size, len, 16);
+			if (ret)
+				goto err;
+		}
+		bulklen -= xfer_size;
 	}
 
 	dediprog_set_leds(LED_PASS);

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