Merge tag 'spi-v3.14-2' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi

Pull spi updates from Mark Brown:
 "A respun version of the merges for the pull request previously sent
  with a few additional fixes.  The last two merges were fixed up by
  hand since the branches have moved on and currently have the prior
  merge in them.

  Quite a busy release for the SPI subsystem, mostly in cleanups big and
  small scattered through the stack rather than anything else:

   - New driver for the Broadcom BC63xx HSSPI controller
   - Fix duplicate device registration for ACPI
   - Conversion of s3c64xx to DMAEngine (this pulls in platform and DMA
     changes upon which the transiton depends)
   - Some small optimisations to reduce the amount of time we hold locks
     in the datapath, eliminate some redundant checks and the size of a
     spi_transfer
   - Lots of fixes, cleanups and general enhancements to drivers,
     especially the rspi and Atmel drivers"

* tag 'spi-v3.14-2' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi: (112 commits)
  spi: core: Fix transfer failure when master->transfer_one returns positive value
  spi: Correct set_cs() documentation
  spi: Clarify transfer_one() w.r.t. spi_finalize_current_transfer()
  spi: Spelling s/finised/finished/
  spi: sc18is602: Convert to use bits_per_word_mask
  spi: Remove duplicate code to set default bits_per_word setting
  spi/pxa2xx: fix compilation warning when !CONFIG_PM_SLEEP
  spi: clps711x: Add MODULE_ALIAS to support module auto-loading
  spi: rspi: Add missing clk_disable() calls in error and cleanup paths
  spi: rspi: Spelling s/transmition/transmission/
  spi: rspi: Add support for specifying CPHA/CPOL
  spi/pxa2xx: initialize DMA channels to -1 to prevent inadvertent match
  spi: rspi: Add more QSPI register documentation
  spi: rspi: Add more RSPI register documentation
  spi: rspi: Remove dependency on DMAE for SHMOBILE
  spi/s3c64xx: Correct indentation
  spi: sh: Use spi_sh_clear_bit() instead of open-coded
  spi: bitbang: Grammar s/make to make/to make/
  spi: sh-hspi: Spelling s/recive/receive/
  spi: core: Improve tx/rx_nbits check comments
  ...

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;
 }