[U-Boot] [PATCH v2] spi: mxc_spi: Set master mode for all channels
Fabio Estevam
festevam at gmail.com
Wed Apr 10 01:06:25 CEST 2013
From: Fabio Estevam <fabio.estevam at freescale.com>
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 at freescale.com>
---
Changes since v1:
- Introduce MXC_CSPICTRL_MODE_MASK definition
- Remove additional read of reg_ctrl
arch/arm/include/asm/arch-mx5/imx-regs.h | 1 +
arch/arm/include/asm/arch-mx6/imx-regs.h | 1 +
drivers/spi/mxc_spi.c | 17 +++++++++--------
3 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/arch/arm/include/asm/arch-mx5/imx-regs.h b/arch/arm/include/asm/arch-mx5/imx-regs.h
index 249d15a..a71cc13 100644
--- a/arch/arm/include/asm/arch-mx5/imx-regs.h
+++ b/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)
diff --git a/arch/arm/include/asm/arch-mx6/imx-regs.h b/arch/arm/include/asm/arch-mx6/imx-regs.h
index eaa7439..d79ab2f 100644
--- a/arch/arm/include/asm/arch-mx6/imx-regs.h
+++ b/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)
diff --git a/drivers/spi/mxc_spi.c b/drivers/spi/mxc_spi.c
index 4c19e0b..20419e6 100644
--- a/drivers/spi/mxc_spi.c
+++ b/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(®s->ctrl, 0);
- reg_write(®s->ctrl, MXC_CSPICTRL_EN);
-
- reg_ctrl = reg_read(®s->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(®s->ctrl, reg_ctrl);
+ reg_ctrl |= MXC_CSPICTRL_EN;
+ reg_write(®s->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;
--
1.7.9.5
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