diff options
Diffstat (limited to 'drivers/spi/spi-imx.c')
| -rw-r--r-- | drivers/spi/spi-imx.c | 27 |
1 files changed, 25 insertions, 2 deletions
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index b80f2f70fef..a5474ef9d2a 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; } |