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From: Taniya Das <>
To: Stephen Boyd <>,
	Michael Turquette <>
Cc: Andy Gross <>,
	David Brown <>,
	Rajendra Nayak <>,,,,
Subject: Re: [PATCH v6] clk: qcom: Add lpass clock controller driver for SDM845
Date: Wed, 17 Oct 2018 17:07:29 +0530	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Hello Stephen,

On 10/12/2018 11:05 PM, Stephen Boyd wrote:
> Quoting Taniya Das (2018-10-09 23:12:27)
>> On 10/10/2018 2:22 AM, Stephen Boyd wrote:
>>> Quoting Taniya Das (2018-10-09 10:26:38)
>>>> Hello Stephen,
>>>> On 10/8/2018 8:14 AM, Stephen Boyd wrote:
>>>>> Quoting Taniya Das (2018-10-04 05:02:26)
>>>>>> Add support for the lpass clock controller found on SDM845 based devices.
>>>>>> This would allow lpass peripheral loader drivers to control the clocks to
>>>>>> bring the subsystem out of reset.
>>>>>> LPASS clocks present on the global clock controller would be registered
>>>>>> with the clock framework based on the device tree flag. Also do not gate
>>>>>> these clocks if they are left unused.
>>>>> Why not gate them? This statement states what the code is doing, not why
>>>>> it's doing it which is the more crucial information that should be
>>>>> described in the commit text. Also, please add a comment about it to the
>>>>> code next to the flag.
>>>>> I am concerned that it doesn't make any sense though, so probably it
>>>>> shouldn't be marked as CLK_IGNORE_UNUSED and it's papering over some
>>>>> other larger bug that needs to be fixed.
>>>> It does not have any bug, it is just that to access these lpass
>>>> registers we would need the GCC lpass registers to be enabled. I would
>>>> update the same in the commit text.
>>>> During clock late_init these clocks should not be accessed to check the
>>>> clock status as they would result in unclocked access. The client would
>>>> request these clocks in the correct order and it would not have any issue.
>>> That seems like the bug right there. If the LPASS registers can't be
>>> accessed unless the clks in GCC are enabled then this driver needs to
>>> turn the clks on before reading/writing registers. Marking the clks as
>>> ignore unused is skipping around the real problem.
>> If the driver requests for the clocks they would maintain the order. But
>> if the clock late init call is invoked before the driver requests, there
>> is no way I could manage this dependency, that is the only reason to
>> mark them unused.
> Which driver are we talking about here? The lpass clk driver? Presumably
> the lpass clk driver would request the GCC clks and turn them on in
> probe and then register any lpass clks. If the lpass clk driver probes
> bfeore late init, then the gcc clks will be enabled and everything
> works, and if the lpass clk driver probes after late init then the clks
> that can't be touched without gcc clks enabled won't be registered, and
> then they won't be touched. What goes wrong?

Okay, sure, I will take the GCC clock handles and then enable/disable 
them accordingly.

QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation.


  reply	other threads:[~2018-10-17 11:37 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-04 12:02 [PATCH v6] Add support for LPASS clock controller for SDM845 Taniya Das
2018-10-04 12:02 ` [PATCH v6] clk: qcom: Add lpass clock controller driver " Taniya Das
2018-10-08  2:44   ` Stephen Boyd
2018-10-09 17:26     ` Taniya Das
2018-10-09 20:52       ` Stephen Boyd
2018-10-10  6:12         ` Taniya Das
2018-10-12 17:35           ` Stephen Boyd
2018-10-17 11:37             ` Taniya Das [this message]
2018-10-17 12:04               ` Taniya Das
2018-10-17 14:20                 ` Stephen Boyd
2018-10-19 10:39                   ` Taniya Das
2018-10-25 10:51                     ` tdas
2018-10-29 18:44                       ` Stephen Boyd

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