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Date: Fri, 3 Apr 2015 13:39:31 -0700
From: Aaron Brice <aaron.brice@...asoft.com>
To: broonie@...nel.org
Cc: linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org,
stefan@...er.ch, devicetree@...r.kernel.org
Subject: [PATCH v3 3/3] 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: Aaron Brice <aaron.brice@...asoft.com>
---
drivers/spi/spi-fsl-dspi.c | 64 +++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 60 insertions(+), 4 deletions(-)
diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 8213358..5fe54cd 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -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
@@ -176,6 +179,40 @@ 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;
@@ -354,7 +391,10 @@ 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;
@@ -371,18 +411,34 @@ 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);
--
2.1.0
--
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