From mboxrd@z Thu Jan 1 00:00:00 1970 From: Taniya Das Subject: Re: [PATCH v1] clk: qcom: lpass: Add CLK_IGNORE_UNUSED for lpass clocks Date: Mon, 7 Jan 2019 11:56:00 +0530 Message-ID: References: <1545306385-31240-1-git-send-email-tdas@codeaurora.org> <154533989563.79149.10213938035592547726@swboyd.mtv.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <154533989563.79149.10213938035592547726@swboyd.mtv.corp.google.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Stephen Boyd , Michael Turquette Cc: Andy Gross , David Brown , Rajendra Nayak , linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-arm-msm@vger.kernel.org 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 > >> @@ -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. --