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authorRobin Murphy <robin.murphy@arm.com>2020-06-16 03:09:29 +0300
committerMark Brown <broonie@kernel.org>2020-07-02 00:19:31 +0300
commit26751de25d255eab7132a8024a893609456996e6 (patch)
treeadc12a0981341388ab0b16932168cfe176ff12ca /drivers/spi/spi-bcm2835.c
parentafe7e36360f4c981fc03ef07a81cb4ce3d567325 (diff)
downloadlinux-26751de25d255eab7132a8024a893609456996e6.tar.xz
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.c18
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)