linux-kernel - Re: [PATCH] arm64: dts: msm8916: Move smem below hwlock

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Date:	Tue, 23 Feb 2016 19:28:35 +0000
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Georgi Djakov <georgi.djakov@...aro.org>, andy.gross@...aro.org
Cc:	devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: msm8916: Move smem below hwlock



On 23/02/16 18:47, Georgi Djakov wrote:
> On 23.02.16 г. 19:29, Srinivas Kandagatla wrote:
>>
>>
>> On 23/02/16 17:21, Georgi Djakov wrote:
>>> When the SMEM is probed it defers as it depends on the hardware lock, which
>>> is not available yet. But the SMD bus and RPM regulators and clocks depend
>>> on SMEM and they defer too. The problem with this is that the order of
>>> registering the devices is not optimal and also we may end with messed
>>> up serial console as the RPM clocks are not registered yet..
>> I noticed the same issue but was wondering why would we end up with messed up serial console?
>>
>> Could you add more details on why serial console is messed up?
>>
>> I thought, serial driver has nothing to do with the rpm clocks directly!
>>
>
> If we don't have the rpm clocks registered, the uart clock is an orphan
> and when clk_get_rate() is called on orphan clocks it returns 0 as rate.
Shouldn't the actual uart clk provider registration fail/defer probe due 
to missing parent in this case?

--srini
> In our case the msm_serial driver calls clk_get_rate() and gets 0 rate
> as the parent rpm clock has not registered yet. The result is that the
> baudrate is set incorrectly.
>
> BR,
> Georgi
>