On Tue, 25 Jun 2019 16:13:25 +0300
Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx> wrote:
> Some devices like the ADIS16460 IMU require a stall period between
> transfers, i.e. between when the CS is de-asserted and re-asserted. The
> default value of 10us is not enough. This change makes the delay
> configurable for when the next CS change goes active.
>
> Signed-off-by: Michael Hennerich <michael.hennerich@xxxxxxxxxx>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
General principle seems fine to me, though naming may need some work.
cs_low_time or something more specific than stall perhaps?
+CC Mark.
> ---
> drivers/spi/spi.c | 3 ++-
> include/linux/spi/spi.h | 3 +++
> 2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> index 5e75944ad5d1..739de0118ee1 100644
> --- a/drivers/spi/spi.c
> +++ b/drivers/spi/spi.c
> @@ -1163,7 +1163,8 @@ static int spi_transfer_one_message(struct spi_controller *ctlr,
> keep_cs = true;
> } else {
> spi_set_cs(msg->spi, false);
> - udelay(10);
> + udelay(xfer->cs_change_stall_delay_us ?
> + xfer->cs_change_stall_delay_us : 10);
> spi_set_cs(msg->spi, true);
> }
> }
> diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
> index 053abd22ad31..d23add3b4790 100644
> --- a/include/linux/spi/spi.h
> +++ b/include/linux/spi/spi.h
> @@ -734,6 +734,8 @@ extern void spi_res_release(struct spi_controller *ctlr,
> * transfer. If 0 the default (from @spi_device) is used.
> * @bits_per_word: select a bits_per_word other than the device default
> * for this transfer. If 0 the default (from @spi_device) is used.
> + * @cs_change_stall_delay_us: microseconds to delay between cs_change
> + * transfers.
> * @cs_change: affects chipselect after this transfer completes
> * @delay_usecs: microseconds to delay after this transfer before
> * (optionally) changing the chipselect status, then starting
> @@ -823,6 +825,7 @@ struct spi_transfer {
> #define SPI_NBITS_QUAD 0x04 /* 4bits transfer */
> u8 bits_per_word;
> u8 word_delay_usecs;
> + u8 cs_change_stall_delay_us;
> u16 delay_usecs;
> u32 speed_hz;
> u16 word_delay;
