2021-01-02 03:07:55

by Xu Yilun

Subject: [PATCH v2] spi: fix the divide by 0 error when calculating xfer waiting time

The xfer waiting time is the result of xfer->len / xfer->speed_hz. This
patch makes the assumption of 1khz xfer speed if the xfer->speed_hz is
not assigned and stays 0. This avoids the divide by 0 issue and ensures
a reasonable tolerant waiting time.

Signed-off-by: Xu Yilun <[email protected]>
---
v2: use the normal conditional statement instead of the ternery operator
change the default xfer speed from 1khz to 100khz
---
drivers/spi/spi.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 51d7c00..aacae88 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1108,6 +1108,7 @@ static int spi_transfer_wait(struct spi_controller *ctlr,
{
struct spi_statistics *statm = &ctlr->statistics;
struct spi_statistics *stats = &msg->spi->statistics;
+ u32 speed_hz = xfer->speed_hz;
unsigned long long ms;

if (spi_controller_is_slave(ctlr)) {
@@ -1116,8 +1117,11 @@ static int spi_transfer_wait(struct spi_controller *ctlr,
return -EINTR;
}
} else {
+ if (!speed_hz)
+ speed_hz = 100000;
+
ms = 8LL * 1000LL * xfer->len;
- do_div(ms, xfer->speed_hz);
+ do_div(ms, speed_hz);
ms += ms + 200; /* some tolerance */

if (ms > UINT_MAX)
--
2.7.4

2021-01-02 14:13:30

by Fabio Estevam

Subject: Re: [PATCH v2] spi: fix the divide by 0 error when calculating xfer waiting time

On Sat, Jan 2, 2021 at 12:07 AM Xu Yilun <[email protected]> wrote:
>
> The xfer waiting time is the result of xfer->len / xfer->speed_hz. This
> patch makes the assumption of 1khz xfer speed if the xfer->speed_hz is

You missed to update the commit log to 100kHz.

2021-01-04 03:35:52

by Xu Yilun

Subject: Re: [PATCH v2] spi: fix the divide by 0 error when calculating xfer waiting time

On Sat, Jan 02, 2021 at 11:11:14AM -0300, Fabio Estevam wrote:
> On Sat, Jan 2, 2021 at 12:07 AM Xu Yilun <[email protected]> wrote:
> >
> > The xfer waiting time is the result of xfer->len / xfer->speed_hz. This
> > patch makes the assumption of 1khz xfer speed if the xfer->speed_hz is
>
> You missed to update the commit log to 100kHz.

Thanks for the catching, I'll fix it.

Yilun