Unverified Commit d5864e5b authored by Martin Sperl's avatar Martin Sperl Committed by Mark Brown
Browse files

spi: core: allow defining time that cs is deasserted as a multiple of SCK 



Support setting a delay between cs assert and deassert as
a multiple of spi clock length.

Signed-off-by: default avatarMartin Sperl <kernel@martin.sperl.org>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 0ff2de8b

drivers/spi/spi.c

+8 −0
Original line number Diff line number Diff line
@@ -1111,6 +1111,7 @@ static void _spi_transfer_cs_change_delay(struct spi_message *msg, 
{

	u32 delay = xfer->cs_change_delay;

	u32 unit = xfer->cs_change_delay_unit;

	u32 hz;



	/* return early on "fast" mode - for everything but USECS */

	if (!delay && unit != SPI_DELAY_UNIT_USECS)
@@ -1126,6 +1127,13 @@ static void _spi_transfer_cs_change_delay(struct spi_message *msg, 
		break;

	case SPI_DELAY_UNIT_NSECS: /* nothing to do here */

		break;

	case SPI_DELAY_UNIT_SCK:

		/* if there is no effective speed know, then approximate

		 * by underestimating with half the requested hz

		 */

		hz = xfer->effective_speed_hz ?: xfer->speed_hz / 2;

		delay *= DIV_ROUND_UP(1000000000, hz);

		break;

	default:

		dev_err_once(&msg->spi->dev,

			     "Use of unsupported delay unit %i, using default of 10us\n",

include/linux/spi/spi.h

+1 −0
Original line number Diff line number Diff line
@@ -831,6 +831,7 @@ struct spi_transfer { 
	u8		cs_change_delay_unit;

#define SPI_DELAY_UNIT_USECS	0

#define SPI_DELAY_UNIT_NSECS	1

#define SPI_DELAY_UNIT_SCK	2

	u32		speed_hz;

	u16		word_delay;

CRA Git | Maintained and supported by SUSTech CRA and CCSE