spi: mxc_spi: Set master mode for all channels

The glitch in the SPI clock line, which commit 3cea335c34 (spi: mxc_spi: Fix spi
clock glitch durant reset) solved, is back now and itwas re-introduced by
commit d36b39bf0d (spi: mxc_spi: Fix ECSPI reset handling).

Actually the glitch is happening due to always toggling between slave mode
and master mode by configuring the CHANNEL_MODE bits in this reset function.

Since the spi driver only supports master mode, set the mode for all channels
always to master mode in order to have a stable, "glitch-free" SPI clock line.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>

arch/arm/include/asm/arch-mx5/imx-regs.h

@@ -230,6 +230,7 @@
 #define MXC_CSPICTRL_EN		(1 << 0)
 #define MXC_CSPICTRL_MODE	(1 << 1)
 #define MXC_CSPICTRL_XCH	(1 << 2)
+#define MXC_CSPICTRL_MODE_MASK	(0xf << 4)
 #define MXC_CSPICTRL_CHIPSELECT(x)	(((x) & 0x3) << 12)
 #define MXC_CSPICTRL_BITCOUNT(x)	(((x) & 0xfff) << 20)
 #define MXC_CSPICTRL_PREDIV(x)	(((x) & 0xF) << 12)

arch/arm/include/asm/arch-mx6/imx-regs.h

@@ -346,6 +346,7 @@ struct cspi_regs {
 #define MXC_CSPICTRL_EN		(1 << 0)
 #define MXC_CSPICTRL_MODE	(1 << 1)
 #define MXC_CSPICTRL_XCH	(1 << 2)
+#define MXC_CSPICTRL_MODE_MASK (0xf << 4)
 #define MXC_CSPICTRL_CHIPSELECT(x)	(((x) & 0x3) << 12)
 #define MXC_CSPICTRL_BITCOUNT(x)	(((x) & 0xfff) << 20)
 #define MXC_CSPICTRL_PREDIV(x)	(((x) & 0xF) << 12)

drivers/spi/mxc_spi.c

@@ -137,11 +137,15 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 		return -1;
 	}
 
-	/* Reset spi */
-	reg_write(&regs->ctrl, 0);
-	reg_write(&regs->ctrl, MXC_CSPICTRL_EN);
-
-	reg_ctrl = reg_read(&regs->ctrl);
+	/*
+	 * Reset SPI and set all CSs to master mode, if toggling
+	 * between slave and master mode we might see a glitch
+	 * on the clock line
+	 */
+	reg_ctrl = MXC_CSPICTRL_MODE_MASK;
+	reg_write(&regs->ctrl, reg_ctrl);
+	reg_ctrl |=  MXC_CSPICTRL_EN;
+	reg_write(&regs->ctrl, reg_ctrl);
 
 	/*
 	 * The following computation is taken directly from Freescale's code.
@@ -174,9 +178,6 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs,
 	reg_ctrl = (reg_ctrl & ~MXC_CSPICTRL_POSTDIV(0x0F)) |
 		MXC_CSPICTRL_POSTDIV(post_div);
 
-	/* always set to master mode */
-	reg_ctrl |= 1 << (cs + 4);
-
 	/* We need to disable SPI before changing registers */
 	reg_ctrl &= ~MXC_CSPICTRL_EN;