spi_flash: Move (de-)assertion of /CS to single location

This consolidates all calls to spi_claim_bus() and spi_release_bus()
to a single location where spi_xfer() is called. This avoids confusing
(and potentially redundant) calls that were being done throughout the
generic spi_flash.c functions and chip-specific functions.

I don't think the current approach could even work since many chip
drivers assert /CS once and then issue multiple commands such as page
program followed by reading the status register. I suspect the reason
we didn't notice it on x86 is because the ICH/PCH handled each
individual command correctly (spi_claim_bus() and spi_release_bus()
are noops) in spite of the broken code.

BUG=none
BRANCH=none
TEST=tested on nyan and link
Signed-off-by: David Hendricks <dhendrix@chromium.org>

Original-Change-Id: I3257e2f6a2820834f4c9018069f90fcf2bab05f6
Original-Reviewed-on: https://chromium-review.googlesource.com/194510
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Original-Commit-Queue: David Hendricks <dhendrix@chromium.org>
Original-Tested-by: David Hendricks <dhendrix@chromium.org>
(cherry picked from commit d3394d34fb49e9e252f67371674d5b3aa220bc9e)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: Ieb62309b18090d8f974f91a6e448af3d65dd3d1d
Reviewed-on: http://review.coreboot.org/7829
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

1 files changed, 1 insertions, 7 deletions

diff --git a/src/drivers/spi/sst.c b/src/drivers/spi/sst.c
index d81888a709..f681b7eeba 100644
--- a/src/drivers/spi/sst.c
+++ b/src/drivers/spi/sst.c
@@ -146,15 +146,10 @@ static int
 sst_write(struct spi_flash *flash, u32 offset, size_t len, const void *buf)
 {
 	size_t actual, cmd_len;
-	int ret;
+	int ret = 0;
 	u8 cmd[4];
 
 	flash->spi->rw = SPI_WRITE_FLAG;
-	ret = spi_claim_bus(flash->spi);
-	if (ret) {
-		printk(BIOS_WARNING, "SF: Unable to claim SPI bus\n");
-		return ret;
-	}
 
 	/* If the data is not word aligned, write out leading single byte */
 	actual = offset % 2;
@@ -209,7 +204,6 @@ done:
 	printk(BIOS_SPEW, "SF: SST: program %s %zu bytes @ 0x%lx\n",
 	      ret ? "failure" : "success", len, (unsigned long)offset - actual);
 #endif
-	spi_release_bus(flash->spi);
 	return ret;
 }