[PATCH 2/2] serial: amba-pl011: complete support to ZTE uart

[G Gregory]

On 22 March 2016 at 02:17, Jun Nie <jun.nie at linaro.org> wrote:
> 2016-03-22 10:06 GMT+08:00 Timur Tabi <timur at codeaurora.org>:
>> Jun Nie wrote:
>>>
>>> That's a fair comment. I suppose all platform need to enable clock for
>>> the device. For device tree case, we need these code for clock
>>> enabling.
>>
>>
>> But why do you need to enable the clock?  The pl011 driver works fine for
>> every platform without your patch.  If the ZTE platform needs to call
>> clk_get() in order to work, than that is something different about your
>> platform.
>
> ARM/ST pl011 is amba device and use pl011_probe() for initialization,
> which call these clock enabling code for every device. You introduced
> platform device driver entry for pl011 and only sbsa use platform
> device probe method currently. I am trying to reuse this probe
> function, so need to add clock enabling code in this function.
>
> If you did not find any issue in sbsa device tree case, I guess the
> clock is always enabled. For mobile platform, clock is auto gated for
> power saving in most of cases.
>
>>
>>> For ACPI case, it may be handled automatically. If you agree
>>> my opinion, I will move these lines to patch 1. Please correct me if I
>>> am wrong.
>>
>>
>> I think you need to create a separate patch that adds that call, and make
>> sure it's tested by other platforms before it gets accepted.
>
> These code only impact sbsa device as only sbsa device is initialized
> via platform driver entry. So only your flavor is need for testing the
> code. Thanks! :-)
>
In SBSA mode the UART clock is always enabled by the firmware and
there are no baud rate registers so we don't need to know the value of
the clock. In ACPI there is no method to represent the clock. So if
you add lines to unconditionally require a clock you will break SBSA
mode in ACPI.

Graeme