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Subject[RFC PATCH 08/15] spi: core,atmel: convert `word_delay_usecs` -> `word_delay` for spi_device
Date
This change does a conversion from the `word_delay_usecs` -> `word_delay`
for the `spi_device` struct.

This allows users to specify inter-word delays in other unit types
(nano-seconds or clock cycles), depending on how users want.

The Atmel SPI driver is the only current user of the `word_delay_usecs`
field (from the `spi_device` struct).
So, it needed a slight conversion to use the `word_delay` as an `spi_delay`
struct.

In SPI core, the only required mechanism is to update the `word_delay`
information per `spi_transfer`. This requires a bit more logic than before,
because it needs that both delays be converted to a common unit
(nano-seconds) for comparison.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---
drivers/spi/spi-atmel.c | 26 ++++++++++++++++++++++++--
drivers/spi/spi.c | 24 ++++++++++++++++++++++--
include/linux/spi/spi.h | 7 ++-----
3 files changed, 48 insertions(+), 9 deletions(-)

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index f00b367523cd..009bb4fb5e5f 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -1172,12 +1172,31 @@ atmel_spi_pdc_interrupt(int irq, void *dev_id)
return ret;
}

+static int atmel_word_delay_csr(struct spi_device *spi, struct atmel_spi *as)
+{
+ struct spi_delay *delay = &spi->word_delay;
+ u32 value = delay->value;
+
+ switch (delay->unit) {
+ case SPI_DELAY_UNIT_NSECS:
+ value /= 1000;
+ break;
+ case SPI_DELAY_UNIT_USECS:
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ return (as->spi_clk / 1000000 * value) >> 5;
+}
+
static int atmel_spi_setup(struct spi_device *spi)
{
struct atmel_spi *as;
struct atmel_spi_device *asd;
u32 csr;
unsigned int bits = spi->bits_per_word;
+ int word_delay_csr;

as = spi_master_get_devdata(spi->master);

@@ -1201,11 +1220,14 @@ static int atmel_spi_setup(struct spi_device *spi)
*/
csr |= SPI_BF(DLYBS, 0);

+ word_delay_csr = atmel_word_delay_csr(as, spi);
+ if (word_delay_csr < 0)
+ return word_delay_csr;
+
/* DLYBCT adds delays between words. This is useful for slow devices
* that need a bit of time to setup the next transfer.
*/
- csr |= SPI_BF(DLYBCT,
- (as->spi_clk / 1000000 * spi->word_delay_usecs) >> 5);
+ csr |= SPI_BF(DLYBCT, word_delay_csr);

asd = spi->controller_state;
if (!asd) {
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index d0bf0ffca042..ba8731b77753 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -3159,6 +3159,26 @@ void spi_set_cs_timing(struct spi_device *spi, u8 setup, u8 hold,
}
EXPORT_SYMBOL_GPL(spi_set_cs_timing);

+static int _spi_xfer_word_delay_update(struct spi_transfer *xfer,
+ struct spi_device *spi)
+{
+ int delay1, delay2;
+
+ delay1 = _spi_delay_to_ns(&xfer->word_delay, xfer);
+ if (delay1 < 0)
+ return delay1;
+
+ delay2 = _spi_delay_to_ns(&spi->word_delay, xfer);
+ if (delay2 < 0)
+ return delay2;
+
+ if (delay1 < delay2)
+ memcpy(&xfer->word_delay, &spi->word_delay,
+ sizeof(xfer->word_delay));
+
+ return 0;
+}
+
static int __spi_validate(struct spi_device *spi, struct spi_message *message)
{
struct spi_controller *ctlr = spi->controller;
@@ -3294,8 +3314,8 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message)
return -EINVAL;
}

- if (xfer->word_delay_usecs < spi->word_delay_usecs)
- xfer->word_delay_usecs = spi->word_delay_usecs;
+ if (_spi_xfer_word_delay_update(xfer, spi))
+ return -EINVAL;
}

message->status = -EINPROGRESS;
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 16397b210e0c..e7ec0be16a82 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -138,7 +138,7 @@ extern int spi_delay_exec(struct spi_delay *_delay, struct spi_transfer *xfer);
* the spi_master.
* @cs_gpiod: gpio descriptor of the chipselect line (optional, NULL when
* not using a GPIO line)
- * @word_delay_usecs: microsecond delay to be inserted between consecutive
+ * @word_delay: delay to be inserted between consecutive
* words of a transfer
*
* @statistics: statistics for the spi_device
@@ -188,7 +188,7 @@ struct spi_device {
const char *driver_override;
int cs_gpio; /* LEGACY: chip select gpio */
struct gpio_desc *cs_gpiod; /* chip select gpio desc */
- uint8_t word_delay_usecs; /* inter-word delay */
+ struct spi_delay word_delay; /* inter-word delay */

/* the statistics */
struct spi_statistics statistics;
@@ -757,8 +757,6 @@ extern void spi_res_release(struct spi_controller *ctlr,
* @delay_usecs: microseconds to delay after this transfer before
* (optionally) changing the chipselect status, then starting
* the next transfer or completing this @spi_message.
- * @word_delay_usecs: microseconds to inter word delay after each word size
- * (set by bits_per_word) transmission.
* @word_delay: inter word delay to be introduced after each word size
* (set by bits_per_word) transmission.
* @effective_speed_hz: the effective SCK-speed that was used to
@@ -844,7 +842,6 @@ struct spi_transfer {
#define SPI_NBITS_DUAL 0x02 /* 2bits transfer */
#define SPI_NBITS_QUAD 0x04 /* 4bits transfer */
u8 bits_per_word;
- u8 word_delay_usecs;
u16 delay_usecs;
struct spi_delay cs_change_delay;
struct spi_delay word_delay;
--
2.20.1
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