[PATCH] spi/pxa2xx: fix incorrect SW mode chipselect setting for BayTrail LPSS SPI

[PATCH] spi/pxa2xx: fix incorrect SW mode chipselect setting for BayTrail LPSS SPI

[Chew Chiau Ee]

From: Chew, Chiau Ee <chiau.ee.chew@intel.com>

It was observed that after module removal followed by insertion,
the SW mode chipselect is not properly set. Thus causing transfer
failure due to incorrect CS toggling.

Signed-off-by: Chew, Chiau Ee <chiau.ee.chew@intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/spi/spi-pxa2xx.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/spi/spi-pxa2xx.c b/drivers/spi/spi-pxa2xx.c
index a98df7e..cfaf3e6 100644
--- a/drivers/spi/spi-pxa2xx.c
+++ b/drivers/spi/spi-pxa2xx.c
@@ -126,7 +126,7 @@ static void lpss_ssp_setup(struct driver_data *drv_data)
 		goto detection_done;
 	}
 
-	value &= ~SPI_CS_CONTROL_SW_MODE;
+	orig = value &= ~SPI_CS_CONTROL_SW_MODE;
 	writel(value, drv_data->ioaddr + offset + SPI_CS_CONTROL);
 	value = readl(drv_data->ioaddr + offset + SPI_CS_CONTROL);
 	if (value != orig) {
-- 
1.7.4.4

Re: [PATCH] spi/pxa2xx: fix incorrect SW mode chipselect setting for BayTrail LPSS SPI

[Mark Brown]

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On Wed, Jun 11, 2014 at 11:57:02PM +0800, Chew Chiau Ee wrote:

> It was observed that after module removal followed by insertion,
> the SW mode chipselect is not properly set. Thus causing transfer
> failure due to incorrect CS toggling.

> -	value &= ~SPI_CS_CONTROL_SW_MODE;
> +	orig = value &= ~SPI_CS_CONTROL_SW_MODE;
>  	writel(value, drv_data->ioaddr + offset + SPI_CS_CONTROL);
>  	value = readl(drv_data->ioaddr + offset + SPI_CS_CONTROL);
>  	if (value != orig) {

This is a *really* non-obvious fix, I'd have expected the original value
to be re-read from the hardware here rather than just tweaked, or at
least some comment explaining what's going on.  Possibly also saving to
a differently named temporary variable would do it but whatever I had to
go look at the context to figure out what was happening and even there I
was unclear.

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