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

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Message-ID: <56CCA95C.9070207@linaro.org>
Date:	Tue, 23 Feb 2016 20:47:56 +0200
From:	Georgi Djakov <georgi.djakov@...aro.org>
To:	Srinivas Kandagatla <srinivas.kandagatla@...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 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.
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