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path: root/drivers/spi/spi-imx.c
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Diffstat (limited to 'drivers/spi/spi-imx.c')
-rw-r--r--drivers/spi/spi-imx.c27
1 files changed, 25 insertions, 2 deletions
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index b80f2f70fef7..a5474ef9d2a0 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -206,7 +206,8 @@ static unsigned int spi_imx_clkdiv_2(unsigned int fin,
#define MX51_ECSPI_STAT_RR (1 << 3)
/* MX51 eCSPI */
-static unsigned int mx51_ecspi_clkdiv(unsigned int fin, unsigned int fspi)
+static unsigned int mx51_ecspi_clkdiv(unsigned int fin, unsigned int fspi,
+ unsigned int *fres)
{
/*
* there are two 4-bit dividers, the pre-divider divides by
@@ -234,6 +235,10 @@ static unsigned int mx51_ecspi_clkdiv(unsigned int fin, unsigned int fspi)
pr_debug("%s: fin: %u, fspi: %u, post: %u, pre: %u\n",
__func__, fin, fspi, post, pre);
+
+ /* Resulting frequency for the SCLK line. */
+ *fres = (fin / (pre + 1)) >> post;
+
return (pre << MX51_ECSPI_CTRL_PREDIV_OFFSET) |
(post << MX51_ECSPI_CTRL_POSTDIV_OFFSET);
}
@@ -264,6 +269,7 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
struct spi_imx_config *config)
{
u32 ctrl = MX51_ECSPI_CTRL_ENABLE, cfg = 0;
+ u32 clk = config->speed_hz, delay;
/*
* The hardware seems to have a race condition when changing modes. The
@@ -275,7 +281,7 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
ctrl |= MX51_ECSPI_CTRL_MODE_MASK;
/* set clock speed */
- ctrl |= mx51_ecspi_clkdiv(spi_imx->spi_clk, config->speed_hz);
+ ctrl |= mx51_ecspi_clkdiv(spi_imx->spi_clk, config->speed_hz, &clk);
/* set chip select to use */
ctrl |= MX51_ECSPI_CTRL_CS(config->cs);
@@ -297,6 +303,23 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
writel(ctrl, spi_imx->base + MX51_ECSPI_CTRL);
writel(cfg, spi_imx->base + MX51_ECSPI_CONFIG);
+ /*
+ * Wait until the changes in the configuration register CONFIGREG
+ * propagate into the hardware. It takes exactly one tick of the
+ * SCLK clock, but we will wait two SCLK clock just to be sure. The
+ * effect of the delay it takes for the hardware to apply changes
+ * is noticable if the SCLK clock run very slow. In such a case, if
+ * the polarity of SCLK should be inverted, the GPIO ChipSelect might
+ * be asserted before the SCLK polarity changes, which would disrupt
+ * the SPI communication as the device on the other end would consider
+ * the change of SCLK polarity as a clock tick already.
+ */
+ delay = (2 * 1000000) / clk;
+ if (likely(delay < 10)) /* SCLK is faster than 100 kHz */
+ udelay(delay);
+ else /* SCLK is _very_ slow */
+ usleep_range(delay, delay + 10);
+
return 0;
}