Re: [PATCH v2 2/2] spi: Force CS to be in inactive state after off-mode transition

[Gregory CLEMENT <gregory.clement@free-electrons.com>]

On 11/10/2010 04:57 PM, Grant Likely wrote:
> On Wed, Nov 10, 2010 at 11:32:59AM +0100, Gregory CLEMENT wrote:
>> When SPI wake up from OFF mode, CS is in the wrong state: force it
>> to the inactive state.
>>
>> During the system life, I monitored the CS behavior using a
>> oscilloscope. I also activated debug in omap2_mcspi, so I saw when
>> driver disable the clocks and restore context when device is not
>> used.
>> Each time the CS was in the correct state.
>> It was only when system was put suspend to ram with off-mode
>> activated that on resume the CS was in wrong state( ie activated).
>
> Sounds like a bug in the suspend/resume path of the spi_master, not
> the spi_device.  Trying to work around it via the spi_device resume
> path is the wrong approach.
>

OK it was not clear to me that spi_resume() and spi_suspend() were 
specifics to devices as these functions belong to a bus structure.

So you suggest to use the suspend/resume functions of the 
platform_driver structure of omap2_mcspi_driver, right?

> g.
>
>>
>> Signed-off-by: Gregory CLEMENT<gregory.clement@free-electrons.com>
>> ---
>>   drivers/spi/omap2_mcspi.c |   10 ++++++++++
>>   1 files changed, 10 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/spi/omap2_mcspi.c b/drivers/spi/omap2_mcspi.c
>> index 2a651e6..938f14c 100644
>> --- a/drivers/spi/omap2_mcspi.c
>> +++ b/drivers/spi/omap2_mcspi.c
>> @@ -1139,6 +1139,15 @@ static u8 __initdata spi4_txdma_id[] = {
>>   };
>>   #endif
>>   +/* When SPI wake up, CS is in wrong state: force it to unactive state*/
>> +static void omap2_mcspi_resume(struct spi_device *spi)
>> +{
>> +	omap2_mcspi_enable_clocks( spi_master_get_devdata(spi->master));
>> +	/* We need to togle CS state for OMAP take this chang in account*/
>> +	omap2_mcspi_force_cs(spi, 1);
>> +	omap2_mcspi_force_cs(spi, 0);
>> +	omap2_mcspi_disable_clocks( spi_master_get_devdata(spi->master));
>> +}
>>   static int __init omap2_mcspi_probe(struct platform_device *pdev)
>>   {
>>   	struct spi_master	*master;
>> @@ -1194,6 +1203,7 @@ static int __init omap2_mcspi_probe(struct
>> platform_device *pdev)
>>   	master->transfer = omap2_mcspi_transfer;
>>   	master->cleanup = omap2_mcspi_cleanup;
>>   	master->num_chipselect = num_chipselect;
>> +	master->resume = omap2_mcspi_resume;
>>    	dev_set_drvdata(&pdev->dev, master);
>>   -- 1.7.0.4
>>


-- 
Gregory Clement, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com