[U-Boot] [PATCH] spi: tegra: fix hand in set_mode()

[Stephen Warren]

On 08/19/2016 10:56 AM, Jagan Teki wrote:
> On 18 August 2016 at 22:23, Stephen Warren <swarren at wwwdotorg.org> wrote:
>> From: Stephen Warren <swarren at nvidia.com>
>>
>> In tegra20_slink.c, the set_mode() function may be executed before the
>> SPI bus is claimed the first time, and hence the clocks to the SPI
>> controller may not be running. If so, any register read/write at this
>> time will hang the CPU. Fix this by ensuring the clock is running as soon
>> as the driver is probed. This is observed on the Tegra30 Beaver board.
>>
>> Apply the same clock initialization fix to all other Tegra SPI drivers so
>> that if set_mode() is ever implemented there, the same bug will not appear.
>> Note that tegra114_spi.c already operates in this fashion.
>>
>> The clock manipulation code is copied from claim_bus() to probe() rather
>> than moved. This ensures that any calls to set_speed() take effect; the
>> clock can't be set once during probe and left unchanged.
>
> Do we need to set the clock for claim_bus() as well? I think it's
> better to move this on to set_speed so-that any call to set_speed()
> will update the same. I don't think claim_bus would require this
> again.

I explained this in the commit message: The clock rate needs to be set 
in claim_bus() so that the frequency requested by set_speed() is in force.