Il 10/07/23 17:49, Andy Shevchenko ha scritto:
Since the new spi_controller_xfer_timeout() helper appeared,
we may replace open coded variant in spi_transfer_wait().
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
drivers/spi/spi.c | 25 ++-----------------------
include/linux/spi/spi.h | 6 +++++-
2 files changed, 7 insertions(+), 24 deletions(-)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 125dea8fae00..c99ee4164f11 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1342,8 +1342,7 @@ static int spi_transfer_wait(struct spi_controller *ctlr,
{
struct spi_statistics __percpu *statm = ctlr->pcpu_statistics;
struct spi_statistics __percpu *stats = msg->spi->pcpu_statistics;
- u32 speed_hz = xfer->speed_hz;
- unsigned long long ms;
+ unsigned long ms;
if (spi_controller_is_slave(ctlr)) {
if (wait_for_completion_interruptible(&ctlr->xfer_completion)) {
@@ -1351,29 +1350,9 @@ static int spi_transfer_wait(struct spi_controller *ctlr,
return -EINTR;
}
} else {
- if (!speed_hz)
- speed_hz = 100000;
-
- /*
- * For each byte we wait for 8 cycles of the SPI clock.
- * Since speed is defined in Hz and we want milliseconds,
- * use respective multiplier, but before the division,
- * otherwise we may get 0 for short transfers.
- */
- ms = 8LL * MSEC_PER_SEC * xfer->len;
- do_div(ms, speed_hz);
-
- /*
- * Increase it twice and add 200 ms tolerance, use
- * predefined maximum in case of overflow.
- */
- ms += ms + 200;
- if (ms > UINT_MAX)
- ms = UINT_MAX;
-
+ ms = spi_controller_xfer_timeout(ctlr, xfer);
I agree on using helpers, but the logic is slightly changing here: yes it is
unlikely (and also probably useless) to get ms == UINT_MAX, but the helper is
limiting the maximum timeout value to 500mS, which may not work for some slow
controllers/devices.
This should get validated on more than a few platforms, and I'm not sure that
this kind of validation would be "fast" to get... so, probably the best thing
to do here is to add a warning in case the timeout exceeds 500mS, print the
actual value, keep it like this for a kernel version or two and check reports:
that would allow to understand what a safe maximum timeout value could be.
Aside from that, I wouldn't drop those nice comments explaining how/why the
timeout is calculated: I know how, but not everyone knows in advance.
Regards,
Angelo
ms = wait_for_completion_timeout(&ctlr->xfer_completion,
msecs_to_jiffies(ms));
-
if (ms == 0) {
SPI_STATISTICS_INCREMENT_FIELD(statm, timedout);
SPI_STATISTICS_INCREMENT_FIELD(stats, timedout);
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 32c94eae8926..0ce1cb18a076 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -1270,12 +1270,16 @@ static inline bool spi_is_bpw_supported(struct spi_device *spi, u32 bpw)
* that it would take on a single data line and take twice this amount of time
* with a minimum of 500ms to avoid false positives on loaded systems.
*
+ * Assume speed to be 100 kHz if it's not defined at the time of invocation.
+ *
* Returns: Transfer timeout value in milliseconds.
*/
static inline unsigned int spi_controller_xfer_timeout(struct spi_controller *ctlr,
struct spi_transfer *xfer)
{
- return max(xfer->len * 8 * 2 / (xfer->speed_hz / 1000), 500U);
+ u32 speed_hz = xfer->speed_hz ?: 100000;
+
+ return max(xfer->len * 8 * 2 / (speed_hz / 1000), 500U);
}
/*---------------------------------------------------------------------------*/
