diff options
author | Marek Vasut <marex@denx.de> | 2021-07-03 05:23:00 +0300 |
---|---|---|
committer | Mark Brown <broonie@kernel.org> | 2021-07-07 14:01:35 +0300 |
commit | 135cbd378eab336da15de9c84bbb22bf743b38a5 (patch) | |
tree | c7f7b79fe2c8d423f592479d84231fbbc6d8ffe7 /drivers | |
parent | e4a5c19888a5f8a9390860ca493e643be58c8791 (diff) | |
download | linux-135cbd378eab336da15de9c84bbb22bf743b38a5.tar.xz |
spi: imx: mx51-ecspi: Reinstate low-speed CONFIGREG delay
Since 00b80ac935539 ("spi: imx: mx51-ecspi: Move some initialisation to
prepare_message hook."), the MX51_ECSPI_CONFIG write no longer happens
in prepare_transfer hook, but rather in prepare_message hook, however
the MX51_ECSPI_CONFIG delay is still left in prepare_transfer hook and
thus has no effect. This leads to low bus frequency operation problems
described in 6fd8b8503a0dc ("spi: spi-imx: Fix out-of-order CS/SCLK
operation at low speeds") again.
Move the MX51_ECSPI_CONFIG write delay into the prepare_message hook
as well, thus reinstating the low bus frequency fix.
Fixes: 00b80ac935539 ("spi: imx: mx51-ecspi: Move some initialisation to prepare_message hook.")
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20210703022300.296114-1-marex@denx.de
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/spi/spi-imx.c | 38 |
1 files changed, 19 insertions, 19 deletions
diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c index 39dc02e366f4..4aee3db6d6df 100644 --- a/drivers/spi/spi-imx.c +++ b/drivers/spi/spi-imx.c @@ -506,7 +506,7 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx, { struct spi_device *spi = msg->spi; u32 ctrl = MX51_ECSPI_CTRL_ENABLE; - u32 testreg; + u32 testreg, delay; u32 cfg = readl(spi_imx->base + MX51_ECSPI_CONFIG); /* set Master or Slave mode */ @@ -567,6 +567,23 @@ static int mx51_ecspi_prepare_message(struct spi_imx_data *spi_imx, 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) / spi_imx->spi_bus_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; } @@ -574,7 +591,7 @@ static int mx51_ecspi_prepare_transfer(struct spi_imx_data *spi_imx, struct spi_device *spi) { u32 ctrl = readl(spi_imx->base + MX51_ECSPI_CTRL); - u32 clk, delay; + u32 clk; /* Clear BL field and set the right value */ ctrl &= ~MX51_ECSPI_CTRL_BL_MASK; @@ -596,23 +613,6 @@ static int mx51_ecspi_prepare_transfer(struct spi_imx_data *spi_imx, writel(ctrl, spi_imx->base + MX51_ECSPI_CTRL); - /* - * 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; } |