[U-Boot] [U-Boot, PATCHv3, 4/5] spi: ti_qspi: Add delay before xfer for am43xx

[Jagannadha Sutradharudu Teki]

From: "Poddar, Sourav" <sourav.poddar at ti.com>

Without this delay, write/read is failing.
Looks like, the WIP always remain set and hence a timeout
occurs leading to the error.

Without this patch, device does not get probed also.
Here is the log.

U-Boot#
U-Boot#
U-Boot#
U-Boot# sf probe 0
SF: Unsupported flash IDs: manuf ff, jedec ffff, ext_jedec ffff
Failed to initialize SPI flash at 0:0
U-Boot# sf probe 0

While with this patch, log is
U-Boot# sf probe 0
SF: Detected MX25L51235F with page size 256 Bytes, erase size 64 KiB, total 64 MiB, mapped at 30000000
U-Boot# sf erase 0 0x80000
SF: 524288 bytes @ 0x0 Erased: OK
U-Boot# mw 81000000 0xdededede 0x40000
U-Boot# sf write 81000000 0 0x40000
SF: 262144 bytes @ 0x0 Written: OK
U-Boot# sf read 82000000 0 0x40000
SF: 262144 bytes @ 0x0 Read: OK
U-Boot# md 0x82000000

Signed-off-by: Sourav Poddar <sourav.poddar at ti.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jaganna at xilinx.com>
---
V3: Modified commit head, Added review tag
v1->v2:
- updated commit log with error message.
- Add a FIXME comment in code,
 drivers/spi/ti_qspi.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/spi/ti_qspi.c b/drivers/spi/ti_qspi.c
index 5666250..dfa5d0c 100644
--- a/drivers/spi/ti_qspi.c
+++ b/drivers/spi/ti_qspi.c
@@ -285,6 +285,13 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, const void *dout,
 		qslave->cmd |= QSPI_3_PIN;
 	qslave->cmd |= 0xfff;
 
+/* FIXME: This delay is required for successfull
+ * completion of read/write/erase. Once its root
+ * caused, it will be remove from the driver.
+ */
+#ifdef CONFIG_AM43XX
+	udelay(100);
+#endif
 	while (words--) {
 		if (txp) {
 			debug("tx cmd %08x dc %08x data %02x\n",