[PATCH 5.4 15/85] spi: imx: mx51-ecspi: Reinstate low-speed CONFIGREG delay

Greg Kroah-Hartman
2021-08-10T17:36:06Z

From: Marek Vasut <marex@denx.de>

[ Upstream commit 135cbd378eab336da15de9c84bbb22bf743b38a5 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/spi/spi-imx.c | 38 +++++++++++++++++++-------------------
1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index e237481dbbbb..14cebcda0ccc 100644
--- a/drivers/spi/spi-imx.c
+++ b/drivers/spi/spi-imx.c
@@ -498,7 +498,7 @@ 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 */
@@ -559,6 +559,23 @@ 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;
}

@@ -566,7 +583,7 @@ 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;
@@ -588,23 +605,6 @@ 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;
}

--
2.30.2