[PATCH] spi: mvebu: use wait_on_timeout instead of a loop with udelay.
Uwe Kleine-König
u.kleine-koenig at pengutronix.de
Thu Dec 8 02:20:50 PST 2016
This looks nicer and reduces the time to transfer 40 MB at 50 MHz from
203 seconds to 87 seconds.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
---
Side note:
When using
while(!(readl(p->base + SPI_IF_CTRL) & IF_READ_READY))
;
return 0;
instead, the time goes down to 24 seconds.
I think the culprit is that get_time_ns (which is used in
wait_on_timeout) handles conversion from timer values to ns.
I didn't look into that (yet) but I think this could be improved by
changing from:
int __ret = 0;
uint64_t __to_start = get_time_ns();
while (!(condition)) {
if (is_timeout(__to_start, (timeout))) {
__ret = -ETIMEOUT;
break;
}
}
return __ret;
to something like:
int __ret = 0;
uint64_t __to_start_cyc = get_time_cyc();
uint64_t __timeout_cyc = ns2cyc(timeout);
while (!(condition)) {
if (is_timeout_cyc(__to_start_cyc, __timeout_cyc)) {
__ret = -ETIMEOUT;
break;
}
}
return __ret;
Here only a single conversion between cyc and ns is done and
is_timeout_cyc is cheap as it doesn't need to convert.
The obvious downside is that time_ns isn't updated that often. But it
could still be worth the effort.
Best regards
Uwe
drivers/spi/mvebu_spi.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)
diff --git a/drivers/spi/mvebu_spi.c b/drivers/spi/mvebu_spi.c
index 68838c0ce184..f24508a7bc5d 100644
--- a/drivers/spi/mvebu_spi.c
+++ b/drivers/spi/mvebu_spi.c
@@ -249,13 +249,11 @@ static int mvebu_spi_setup(struct spi_device *spi)
static inline int mvebu_spi_wait_for_read_ready(struct mvebu_spi *p)
{
- int timeout = 100;
- while ((readl(p->base + SPI_IF_CTRL) & IF_READ_READY) == 0 &&
- timeout--)
- udelay(1);
- if (timeout < 0)
- return -EIO;
- return 0;
+ int ret;
+
+ ret = wait_on_timeout(100 * USECOND,
+ readl(p->base + SPI_IF_CTRL) & IF_READ_READY);
+ return ret;
}
static int mvebu_spi_do_transfer(struct spi_device *spi,
--
2.10.2
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