From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: [PATCH v4 0/2] clk: qcom: Add support for RCG to register for DFS To: Stephen Boyd , Michael Turquette Cc: Andy Gross , David Brown , Rajendra Nayak , Amit Nischal , linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org, linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org References: <1533952436-17221-1-git-send-email-tdas@codeaurora.org> <153455835372.28926.7641705907931269497@swboyd.mtv.corp.google.com> <693d9cf4-4a6f-feb5-0c3f-ded842bbdf0a@codeaurora.org> <2db97037-b5f1-9234-862c-fa483b8aeb62@codeaurora.org> <153486545785.28926.5289007760649251969@swboyd.mtv.corp.google.com> <4cda3c7e-3ac3-af97-6d9f-24dd5a4efa28@codeaurora.org> <153504874119.28926.4197673432816461627@swboyd.mtv.corp.google.com> <153540388675.129321.14679244317392825384@swboyd.mtv.corp.google.com> From: Taniya Das Message-ID: <531a5894-da72-fb38-dece-87a06c4ff7d6@codeaurora.org> Date: Tue, 28 Aug 2018 14:36:35 +0530 MIME-Version: 1.0 In-Reply-To: <153540388675.129321.14679244317392825384@swboyd.mtv.corp.google.com> Content-Type: text/plain; charset=utf-8; format=flowed List-ID: On 8/28/2018 2:34 AM, Stephen Boyd wrote: > Quoting Stephen Boyd (2018-08-23 11:25:41) >> Quoting Taniya Das (2018-08-22 03:28:31) >>> >>>> >>>> Hmmmm. Ok. That won't work then. recalc_rate() better not try to >>>> populate the frequency table then or it will not work. So I suppose it >>>> needs to fallback to reading the registers and assuming the parent_rate >>>> coming in is the actual frequency of it's parent until the frequency >>>> table pointer is non-NULL. Would that work? >>>> >>> Yes that would work. >> >> Ok. >> >>> >>>> BTW, does DFS switch parents without software knowing about it? >>> DFS would not switch until a HW request is sent, but SW would be unware >>> of the switch except the current_perf_state being updated with the >>> requested level. >>> >>> What >>>> happens in that case? Does the QUP driver make sure that the new parent >>>> of this RCG is properly enabled so that it can switch to it when needed? >>> >>> I am not sure if they poll for any of their QUP HW state to make sure >>> the switch is complete. >>> >>>> I'm still trying to understand this whole design. Who takes care of the >>>> voltage requirements in this case? The QUP driver as well? >>>> >>> >>> When the QUP driver requires to switch to new performance level, the >>> first request would be to set_rate()(QUP driver would get the list of >>> supported frequencies using the clk_round_rate()) which in QCOM clock >>> driver would take care of setting the required voltage for the new >>> parent switch. >> >> It would also make sure that the new parent is enabled if the QUP clk is >> enabled. That's another concern. Does the PLL turn on automatically when >> the RCG switches to it? >> >>> Then the QUP driver would request the HW for a new perf switch which >>> would result to a DFS switch for the QUP clocks. >> >> It sounds like the QUP driver does half of the work via the clk APIs and >> then the other half through the DFS register. Maybe the QUP driver >> should be registering a clk as well for its DFS register so it can all >> be clk API calls here. Something to consider. Anyway, that's not >> important to this patch so here's the updated patch. > > I've squashed this in and applied the patches. > Thanks Stephen. -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation. --