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>
---
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;
--
2.20.1
