[PATCH] Revert "spi: bitbang: only toggle bitchanges"

[Lars Persson <lars.persson@xxxxxxxx>]

This reverts commit 232a5adc5199 ("spi: bitbang: only toggle
bitchanges") because it breaks bitbanged SPI on our MIPS system. I
found two problems with the patch:
- oldbit must initially be computed from bit position 7, 15 or 31 of
  word depending on the value of bits.
- The optimization also does not eliminate consecutive ones because
  the compare of 1<<31 and 1 will be false (a bool only takes values 0
  or 1).

Signed-off-by: Lars Persson <larper@xxxxxxxx>
---
 drivers/spi/spi-bitbang-txrx.h | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/spi/spi-bitbang-txrx.h b/drivers/spi/spi-bitbang-txrx.h
index 06b34e5..c616e41 100644
--- a/drivers/spi/spi-bitbang-txrx.h
+++ b/drivers/spi/spi-bitbang-txrx.h
@@ -49,17 +49,12 @@ bitbang_txrx_be_cpha0(struct spi_device *spi,
 {
 	/* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */
 
-	bool oldbit = !(word & 1);
 	/* clock starts at inactive polarity */
 	for (word <<= (32 - bits); likely(bits); bits--) {
 
 		/* setup MSB (to slave) on trailing edge */
-		if ((flags & SPI_MASTER_NO_TX) == 0) {
-			if ((word & (1 << 31)) != oldbit) {
-				setmosi(spi, word & (1 << 31));
-				oldbit = word & (1 << 31);
-			}
-		}
+		if ((flags & SPI_MASTER_NO_TX) == 0)
+			setmosi(spi, word & (1 << 31));
 		spidelay(nsecs);	/* T(setup) */
 
 		setsck(spi, !cpol);
@@ -81,18 +76,13 @@ bitbang_txrx_be_cpha1(struct spi_device *spi,
 {
 	/* if (cpol == 0) this is SPI_MODE_1; else this is SPI_MODE_3 */
 
-	bool oldbit = !(word & (1 << 31));
 	/* clock starts at inactive polarity */
 	for (word <<= (32 - bits); likely(bits); bits--) {
 
 		/* setup MSB (to slave) on leading edge */
 		setsck(spi, !cpol);
-		if ((flags & SPI_MASTER_NO_TX) == 0) {
-			if ((word & (1 << 31)) != oldbit) {
-				setmosi(spi, word & (1 << 31));
-				oldbit = word & (1 << 31);
-			}
-		}
+		if ((flags & SPI_MASTER_NO_TX) == 0)
+			setmosi(spi, word & (1 << 31));
 		spidelay(nsecs); /* T(setup) */
 
 		setsck(spi, cpol);
-- 
2.1.4

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