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spi: mxc_spi: Set master mode for all channels

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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>
This commit is contained in:
Fabio Estevam 2013-04-09 13:06:25 +00:00 committed by Stefano Babic
parent 66300ac25b
commit 0f1411bc8d
3 changed files with 11 additions and 8 deletions
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1
arch/arm/include/asm/arch-mx5/imx-regs.h
View file

@ -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)

1
arch/arm/include/asm/arch-mx6/imx-regs.h
View file

@ -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)

17
drivers/spi/mxc_spi.c
View file

@ -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;