diff options
| author | Robin Murphy <robin.murphy@arm.com> | 2020-06-16 01:09:29 +0100 |
|---|---|---|
| committer | Mark Brown <broonie@kernel.org> | 2020-07-01 22:19:31 +0100 |
| commit | 26751de25d255eab7132a8024a893609456996e6 (patch) | |
| tree | adc12a0981341388ab0b16932168cfe176ff12ca /drivers/spi/spi-bcm2835.c | |
| parent | afe7e36360f4c981fc03ef07a81cb4ce3d567325 (diff) | |
spi: bcm2835: Micro-optimise FIFO loops
The blind and counted loops are always called with nonzero count, so
convert them to do-while loops that lead to slightly more efficient
code generation. With GCC 8.3 this shaves off 1-2 instructions per
iteration in each case.
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/9242863077acf9a64e4b3720e479855b88d19e82.1592261248.git.robin.murphy@arm.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi/spi-bcm2835.c')
| -rw-r--r-- | drivers/spi/spi-bcm2835.c | 18 |
1 files changed, 8 insertions, 10 deletions
diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c index aec70ac8911e..e9a91adf03eb 100644 --- a/drivers/spi/spi-bcm2835.c +++ b/drivers/spi/spi-bcm2835.c @@ -245,13 +245,13 @@ static inline void bcm2835_rd_fifo_count(struct bcm2835_spi *bs, int count) bs->rx_len -= count; - while (count > 0) { + do { val = bcm2835_rd(bs, BCM2835_SPI_FIFO); len = min(count, 4); memcpy(bs->rx_buf, &val, len); bs->rx_buf += len; count -= 4; - } + } while (count > 0); } /** @@ -271,7 +271,7 @@ static inline void bcm2835_wr_fifo_count(struct bcm2835_spi *bs, int count) bs->tx_len -= count; - while (count > 0) { + do { if (bs->tx_buf) { len = min(count, 4); memcpy(&val, bs->tx_buf, len); @@ -281,7 +281,7 @@ static inline void bcm2835_wr_fifo_count(struct bcm2835_spi *bs, int count) } bcm2835_wr(bs, BCM2835_SPI_FIFO, val); count -= 4; - } + } while (count > 0); } /** @@ -310,12 +310,11 @@ static inline void bcm2835_rd_fifo_blind(struct bcm2835_spi *bs, int count) count = min(count, bs->rx_len); bs->rx_len -= count; - while (count) { + do { val = bcm2835_rd(bs, BCM2835_SPI_FIFO); if (bs->rx_buf) *bs->rx_buf++ = val; - count--; - } + } while (--count); } /** @@ -330,11 +329,10 @@ static inline void bcm2835_wr_fifo_blind(struct bcm2835_spi *bs, int count) count = min(count, bs->tx_len); bs->tx_len -= count; - while (count) { + do { val = bs->tx_buf ? *bs->tx_buf++ : 0; bcm2835_wr(bs, BCM2835_SPI_FIFO, val); - count--; - } + } while (--count); } static void bcm2835_spi_reset_hw(struct bcm2835_spi *bs) |