Commit 95bf15f3 authored by Aaron Brice's avatar Aaron Brice Committed by Mark Brown
Browse files

spi: fsl-dspi: Add ~50ns delay between cs and sck 



Add delay between chip select and clock signals, before clock starts and
after clock stops.

Signed-off-by: default avatarAaron Brice <aaron.brice@datasoft.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent c1c14957

drivers/spi/spi-fsl-dspi.c

+60 −4
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/interrupt.h>

#include <linux/io.h>

#include <linux/kernel.h>

#include <linux/math64.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/of_device.h>
@@ -29,6 +30,7 @@ 
#include <linux/sched.h>

#include <linux/spi/spi.h>

#include <linux/spi/spi_bitbang.h>

#include <linux/time.h>



#define DRIVER_NAME "fsl-dspi"
@@ -51,7 +53,7 @@ 
#define SPI_CTAR_CPOL(x)	((x) << 26)

#define SPI_CTAR_CPHA(x)	((x) << 25)

#define SPI_CTAR_LSBFE(x)	((x) << 24)

#define SPI_CTAR_PCSSCR(x)	(((x) & 0x00000003) << 22)

#define SPI_CTAR_PCSSCK(x)	(((x) & 0x00000003) << 22)

#define SPI_CTAR_PASC(x)	(((x) & 0x00000003) << 20)

#define SPI_CTAR_PDT(x)	(((x) & 0x00000003) << 18)

#define SPI_CTAR_PBR(x)	(((x) & 0x00000003) << 16)
@@ -59,6 +61,7 @@ 
#define SPI_CTAR_ASC(x)	(((x) & 0x0000000f) << 8)

#define SPI_CTAR_DT(x)		(((x) & 0x0000000f) << 4)

#define SPI_CTAR_BR(x)		((x) & 0x0000000f)

#define SPI_CTAR_SCALE_BITS	0xf



#define SPI_CTAR0_SLAVE	0x0c
@@ -174,6 +177,40 @@ static void hz_to_spi_baud(char *pbr, char *br, int speed_hz, 
	}

}



static void ns_delay_scale(char *psc, char *sc, int delay_ns,

		unsigned long clkrate)

{

	int pscale_tbl[4] = {1, 3, 5, 7};

	int scale_needed, scale, minscale = INT_MAX;

	int i, j;

	u32 remainder;



	scale_needed = div_u64_rem((u64)delay_ns * clkrate, NSEC_PER_SEC,

			&remainder);

	if (remainder)

		scale_needed++;



	for (i = 0; i < ARRAY_SIZE(pscale_tbl); i++)

		for (j = 0; j <= SPI_CTAR_SCALE_BITS; j++) {

			scale = pscale_tbl[i] * (2 << j);

			if (scale >= scale_needed) {

				if (scale < minscale) {

					minscale = scale;

					*psc = i;

					*sc = j;

				}

				break;

			}

		}



	if (minscale == INT_MAX) {

		pr_warn("Cannot find correct scale values for %dns delay at clkrate %ld, using max prescaler value",

			delay_ns, clkrate);

		*psc = ARRAY_SIZE(pscale_tbl) - 1;

		*sc = SPI_CTAR_SCALE_BITS;

	}

}



static int dspi_transfer_write(struct fsl_dspi *dspi)

{

	int tx_count = 0;
@@ -352,7 +389,10 @@ static int dspi_setup(struct spi_device *spi) 
{

	struct chip_data *chip;

	struct fsl_dspi *dspi = spi_master_get_devdata(spi->master);

	unsigned char br = 0, pbr = 0, fmsz = 0;

	u32 cs_sck_delay = 0, sck_cs_delay = 0;

	unsigned char br = 0, pbr = 0, pcssck = 0, cssck = 0;

	unsigned char pasc = 0, asc = 0, fmsz = 0;

	unsigned long clkrate;



	if ((spi->bits_per_word >= 4) && (spi->bits_per_word <= 16)) {

		fmsz = spi->bits_per_word - 1;
@@ -369,18 +409,34 @@ static int dspi_setup(struct spi_device *spi) 
			return -ENOMEM;

	}



	of_property_read_u32(spi->dev.of_node, "fsl,spi-cs-sck-delay",

			&cs_sck_delay);



	of_property_read_u32(spi->dev.of_node, "fsl,spi-sck-cs-delay",

			&sck_cs_delay);



	chip->mcr_val = SPI_MCR_MASTER | SPI_MCR_PCSIS |

		SPI_MCR_CLR_TXF | SPI_MCR_CLR_RXF;



	chip->void_write_data = 0;



	hz_to_spi_baud(&pbr, &br,

			spi->max_speed_hz, clk_get_rate(dspi->clk));

	clkrate = clk_get_rate(dspi->clk);

	hz_to_spi_baud(&pbr, &br, spi->max_speed_hz, clkrate);



	/* Set PCS to SCK delay scale values */

	ns_delay_scale(&pcssck, &cssck, cs_sck_delay, clkrate);



	/* Set After SCK delay scale values */

	ns_delay_scale(&pasc, &asc, sck_cs_delay, clkrate);



	chip->ctar_val =  SPI_CTAR_FMSZ(fmsz)

		| SPI_CTAR_CPOL(spi->mode & SPI_CPOL ? 1 : 0)

		| SPI_CTAR_CPHA(spi->mode & SPI_CPHA ? 1 : 0)

		| SPI_CTAR_LSBFE(spi->mode & SPI_LSB_FIRST ? 1 : 0)

		| SPI_CTAR_PCSSCK(pcssck)

		| SPI_CTAR_CSSCK(cssck)

		| SPI_CTAR_PASC(pasc)

		| SPI_CTAR_ASC(asc)

		| SPI_CTAR_PBR(pbr)

		| SPI_CTAR_BR(br);