From d36b39bf0d1dbe4ef03f7fc1f20b2e52eb90acf5 Mon Sep 17 00:00:00 2001 From: Dirk Behme Date: Wed, 20 Mar 2013 22:03:44 +0000 Subject: [PATCH] spi: mxc_spi: Fix ECSPI reset handling Reviewing the ECSPI reset handling shows two issues: 1. For the enable/reset bit (MXC_CSPICTRL_EN) in the control reg (ECSPIx_CONGREG) the i.MX6 technical reference manual states: -- cut -- ECSPIx_CONREG[0]: EN: Writing zero to this bit disables the block and resets the internal logic with the exception of the ECSPI_CONREG. -- cut -- Note the exception mentioned: The CONREG itself isn't reset. Fix this by manually writing the reset value 0 to the whole register. This sets the EN bit to zero, too (i.e. includes the old ~MXC_CSPICTRL_EN). 2. We want to reset the whole SPI block here. So it makes no sense to first read the old value of the CONREG and write it back, later. This will give us the old (historic/random) value of the CONREG back. And doesn't reset the CONREG. To get a clean CONREG after the reset of the block, too, don't use the old (historic/random) value of the CONREG while doing the reset. And read the clean CONREG after the reset. This was found while working on a SPI boot device where the i.MX6 boot ROM has already initialized the SPI block. The initialization by the boot ROM might be different to what the U-Boot driver wants to configure. I.e. we need a clean reset of SPI block, including the CONREG. Signed-off-by: Dirk Behme CC: Stefano Babic CC: Fabio Estevam --- drivers/spi/mxc_spi.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/spi/mxc_spi.c b/drivers/spi/mxc_spi.c index 859c43fee27..4c19e0bf18b 100644 --- a/drivers/spi/mxc_spi.c +++ b/drivers/spi/mxc_spi.c @@ -137,11 +137,11 @@ static s32 spi_cfg_mxc(struct mxc_spi_slave *mxcs, unsigned int cs, return -1; } - reg_ctrl = reg_read(®s->ctrl); - /* Reset spi */ - reg_write(®s->ctrl, (reg_ctrl & ~MXC_CSPICTRL_EN)); - reg_write(®s->ctrl, (reg_ctrl | MXC_CSPICTRL_EN)); + reg_write(®s->ctrl, 0); + reg_write(®s->ctrl, MXC_CSPICTRL_EN); + + reg_ctrl = reg_read(®s->ctrl); /* * The following computation is taken directly from Freescale's code.