Re: [PATCH 2/2] spi: cadence: Configure SPI clock in the prepare_message() callback

[Lars-Peter Clausen <lars-Qo5EllUWu/uELgA04lAiVw@public.gmane.org>]

On 07/10/2014 12:43 PM, Harini Katakam wrote:
> Hi,
>
> On Thu, Jul 10, 2014 at 2:56 PM, Lars-Peter Clausen <lars-Qo5EllUWu/uELgA04lAiVw@public.gmane.org> wrote:
>> Currently the cadence SPI driver does the SPI clock configuration (setup CPOL
>> and CPHA) in the prepare_transfer_hardware() callback. The
>> prepare_transfer_hardware() callback is only called though when the controller
>> transitions from a idle state to a non-idle state. Such a transitions happens
>> when the message queue goes from empty to non-empty. If multiple messages from
>> different SPI slaves with different clock settings are in the message queue the
>> clock settings will not be properly updated when switching from one slave device
>> to another. Instead do the updating of the clock configuration in the
>> prepare_message() callback which will be called for each individual message.
>>
>
> Yes, the requirement from the controller is that CPOL/CPHA setting changes
> will not take effect when SPI is enabled. CPOL/CPHA setting is done in
> prepare_hardware
> before SPI is enabled. So this works.
> According to your patches I understand that you might change CPOL/CPHA for
> each message. Is this possible? Is this a requirement?

The message can be from different SPI devices, so yes this is a requirement. 
I'm seeing the issue in one of my setups.

- Lars

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