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

G Gregory graeme.gregory at linaro.org
Tue Mar 22 01:51:08 PDT 2016

On 22 March 2016 at 08:44, Jun Nie <jun.nie at linaro.org> wrote:
> 2016-03-22 16:20 GMT+08:00 G Gregory <graeme.gregory at linaro.org>:
>> 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
> Right, Timur also already point out breakage of ACPI case. So I plan
> to move clocking enabling code to device tree case handling. Do you
> still have any other concern?
No, I was just making sure ACPI case was clear because it didn't look
so from earlier comments.


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