From: Taniya Das <tdas@codeaurora.org>
To: Stephen Boyd <sboyd@kernel.org>,
Michael Turquette <mturquette@baylibre.com>
Cc: Andy Gross <andy.gross@linaro.org>,
David Brown <david.brown@linaro.org>,
Rajendra Nayak <rnayak@codeaurora.org>,
linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org,
linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1] clk: qcom: lpass: Add CLK_IGNORE_UNUSED for lpass clocks
Date: Mon, 7 Jan 2019 11:56:00 +0530 [thread overview]
Message-ID: <b6397ef1-a6df-0040-9dcc-c491b76a2f8f@codeaurora.org> (raw)
In-Reply-To: <154533989563.79149.10213938035592547726@swboyd.mtv.corp.google.com>
Hello Stephen,
On 12/21/2018 2:34 AM, Stephen Boyd wrote:
> Quoting Taniya Das (2018-12-20 03:46:25)
>> The LPASS clocks has a dependency on the GCC lpass clocks to be enabled
>> before accessing them and that was the reason to mark the gcc lpass clocks
>> as critical. But in the case where the lpass subsystem would require a
>> restart, toggling the lpass reset would from HW clear the SW enable bits
>> of the GCC lpass clocks. Thus the next time bringing up the lpass subsystem
>> out of reset would fail.
>>
>> Allow the lpass clock driver to enable/disable the gcc lpass clocks and
>> mark the lpass clocks not be accessed during late_init if no client vote.
>
> You need to add more details here. It feels like you wrote the beginning
> of a paragraph and then stopped abruptly, leaving the reader hanging for
> the whole story. Why is late_init important? Why do we need to leave
> them on from the bootloader? What if the bootloader doesn't leave them
> enabled? This is all rather hacky so I'm deeply confused. Does the lpass
> driver need to get these gcc clks and enable/prepare them during probe?
> But then it needs to also allow a reset happen and change the clk state?
>
> I suspect this situation is circling a larger problem where a reset is
> toggled and that changes some clk state without the clk framework
> knowing. There's not much we can do about that besides having some
> mechanism for the clks to know that their state is now out of sync. If
> that can be done on the provider driver side then we should have an
> easier time not needing to write a bunch of framework code to handle
> this. OMAP folks are dealing with the same problems from what I recall.
>
Hmm, if I mark the CLK_IS_CRITICAL, I don't see a way to handle it in
provider. Please suggest if you think provider could handle it.
>>
>> Signed-off-by: Taniya Das <tdas@codeaurora.org>
>
>> @@ -77,6 +81,7 @@
>> .enable_mask = BIT(0),
>> .hw.init = &(struct clk_init_data){
>> .name = "lpass_qdsp6ss_sleep_clk",
>> + .flags = CLK_IGNORE_UNUSED,
>
> All uses of CLK_IGNORE_UNUSED and CLK_IS_CRITICAL need comments about
> why they're there. It's never obvious why these things are being done.
>
Sure, would add comments.
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation.
--
next prev parent reply other threads:[~2019-01-07 6:26 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-20 11:46 [PATCH v1] clk: qcom: lpass: Add CLK_IGNORE_UNUSED for lpass clocks Taniya Das
2018-12-20 21:04 ` Stephen Boyd
2019-01-07 6:26 ` Taniya Das [this message]
2019-01-07 21:04 ` Stephen Boyd
2019-01-14 6:12 ` Taniya Das
2019-01-14 22:25 ` Stephen Boyd
2019-01-17 11:19 ` Taniya Das
2019-01-18 19:01 ` Stephen Boyd
2019-01-22 9:31 ` Taniya Das
2019-02-13 7:17 ` Bjorn Andersson
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