spi: core,atmel: convert `word_delay_usecs` -> `word_delay` for spi_device

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>
Link: https://lore.kernel.org/r/20190926105147.7839-8-alexandru.ardelean@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 24 insertions, 2 deletions

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 3ed5e663da6f..1471b049f99a 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -1149,12 +1149,31 @@ 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);
 
@@ -1178,11 +1197,14 @@ static int atmel_spi_setup(struct spi_device *spi)
 	 */
 	csr |= SPI_BF(DLYBS, 0);
 
+	word_delay_csr = atmel_word_delay_csr(spi, as);
+	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) {