From mboxrd@z Thu Jan 1 00:00:00 1970 From: Taniya Das Subject: Re: [PATCH v3 3/3] clk: qcom: Add Global Clock controller (GCC) driver for SC7180 Date: Fri, 27 Sep 2019 13:07:57 +0530 Message-ID: <35f8b699-6ff7-9104-5e3d-ef4ee8635832@codeaurora.org> References: <20190918095018.17979-1-tdas@codeaurora.org> <20190918095018.17979-4-tdas@codeaurora.org> <20190918213946.DC03521924@mail.kernel.org> <20190924231223.9012C207FD@mail.kernel.org> <347780b9-c66b-01c4-b547-b03de2cf3078@codeaurora.org> <20190925130346.42E0820640@mail.kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190925130346.42E0820640@mail.kernel.org> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Stephen Boyd , Michael Turquette , robh+dt@kernel.org Cc: 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, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org Hi Stephen, On 9/25/2019 6:33 PM, Stephen Boyd wrote: > Quoting Taniya Das (2019-09-25 04:20:07) >> Hi Stephen, >> >> Please find my comments. >> >> On 9/25/2019 4:42 AM, Stephen Boyd wrote: >>> Quoting Taniya Das (2019-09-23 01:01:11) >>>> Hi Stephen, >>>> >>>> Thanks for your comments. >>>> >>>> On 9/19/2019 3:09 AM, Stephen Boyd wrote: >>>>> Quoting Taniya Das (2019-09-18 02:50:18) >>>>>> diff --git a/drivers/clk/qcom/gcc-sc7180.c b/drivers/clk/qcom/gcc-sc7180.c >>>>>> new file mode 100644 >>>>>> index 000000000000..d47865d5408f >>>>>> --- /dev/null >>>>>> +++ b/drivers/clk/qcom/gcc-sc7180.c >>>>>> + .ops = &clk_branch2_ops, >>>>>> + }, >>>>>> + }, >>>>>> +}; >>>>>> + >>> [...] >>>>>> +static struct clk_branch gcc_ufs_phy_phy_aux_clk = { >>>>>> + .halt_reg = 0x77094, >>>>>> + .halt_check = BRANCH_HALT, >>>>>> + .hwcg_reg = 0x77094, >>>>>> + .hwcg_bit = 1, >>>>>> + .clkr = { >>>>>> + .enable_reg = 0x77094, >>>>>> + .enable_mask = BIT(0), >>>>>> + .hw.init = &(struct clk_init_data){ >>>>>> + .name = "gcc_ufs_phy_phy_aux_clk", >>>>>> + .parent_data = &(const struct clk_parent_data){ >>>>>> + .hw = &gcc_ufs_phy_phy_aux_clk_src.clkr.hw, >>>>>> + }, >>>>>> + .num_parents = 1, >>>>>> + .flags = CLK_SET_RATE_PARENT, >>>>>> + .ops = &clk_branch2_ops, >>>>>> + }, >>>>>> + }, >>>>>> +}; >>>>>> + >>>>>> +static struct clk_branch gcc_ufs_phy_rx_symbol_0_clk = { >>>>>> + .halt_reg = 0x7701c, >>>>>> + .halt_check = BRANCH_HALT_SKIP, >>>>> >>>>> Again, nobody has fixed the UFS driver to not need to do this halt skip >>>>> check for these clks? It's been over a year. >>>>> >>>> >>>> The UFS_PHY_RX/TX clocks could be left enabled due to certain HW boot >>>> configuration and thus during the late initcall of clk_disable there >>>> could be warnings of "clock stuck ON" in the dmesg. That is the reason >>>> also to use the BRANCH_HALT_SKIP flag. >>> >>> Oh that's bad. Why do the clks stay on when we try to turn them off? >>> >> >> Those could be due to the configuration selected by HW and SW cannot >> override them, so traditionally we have never polled for CLK_OFF for >> these clocks. > > Is that the case or just a guess? > This is the behavior :). >> >>>> >>>> I would also check internally for the UFS driver fix you are referring here. >>> >>> Sure. I keep asking but nothing is done :( >>> >>>> >>>>>> + .clkr = { >>>>>> + .enable_reg = 0x7701c, >>>>>> + .enable_mask = BIT(0), >>>>>> + .hw.init = &(struct clk_init_data){ >>>>>> + .name = "gcc_ufs_phy_rx_symbol_0_clk", >>>>>> + .ops = &clk_branch2_ops, >>>>>> + }, >>>>>> + }, >>>>>> +}; >>>>>> + >>> [...] >>>>>> + >>>>>> +static struct clk_branch gcc_usb3_prim_phy_pipe_clk = { >>>>>> + .halt_reg = 0xf058, >>>>>> + .halt_check = BRANCH_HALT_SKIP, >>>>> >>>>> Why does this need halt_skip? >>>> >>>> This is required as the source is external PHY, so we want to not check >>>> for HALT. >>> >>> This doesn't really answer my question. If the source is an external phy >>> then it should be listed as a clock in the DT binding and the parent >>> should be specified here. Unless something doesn't work because of that? >>> >> >> The USB phy is managed by the USB driver and clock driver is not aware >> if USB driver models the phy as a clock. Thus we do want to keep a >> dependency on the parent and not poll for CLK_ENABLE. > > The clk driver should be aware of the USB driver modeling the phy as a > clk. We do that for other phys so what is the difference here? > Let me check with the USB team, but could we keep them for now? >> >>>> >>>>> >>>>>> + .clkr = { >>>>>> + .enable_reg = 0xf058, >>>>>> + .enable_mask = BIT(0), >>>>>> + .hw.init = &(struct clk_init_data){ >>>>>> + .name = "gcc_usb3_prim_phy_pipe_clk", >>>>>> + .ops = &clk_branch2_ops, >>>>>> + }, >>>>>> + }, >>>>>> +}; >>>>>> + >>>>>> +static struct clk_branch gcc_usb_phy_cfg_ahb2phy_clk = { >>>>>> + .halt_reg = 0x6a004, >>>>>> + .halt_check = BRANCH_HALT, >>>>>> + .hwcg_reg = 0x6a004, >>>>>> + .hwcg_bit = 1, >>>>>> + .clkr = { >>>>>> + .enable_reg = 0x6a004, >>>>>> + .enable_mask = BIT(0), >>>>>> + .hw.init = &(struct clk_init_data){ >>>>>> + .name = "gcc_usb_phy_cfg_ahb2phy_clk", >>>>>> + .ops = &clk_branch2_ops, >>>>>> + }, >>>>>> + }, >>>>>> +}; >>>>>> + >>>>>> +/* Leave the clock ON for parent config_noc_clk to be kept enabled */ >>>>> >>>>> There's no parent though... So I guess this means it keeps it enabled >>>>> implicitly in hardware? >>>>> >>>> >>>> These are not left enabled, but want to leave them enabled for clients >>>> on config NOC. >>> >>> Sure. It just doesn't make sense to create clk structures and expose >>> them in the kernel when we just want to turn the bits on and leave them >>> on forever. Why not just do some register writes in probe for this >>> driver? Doesn't that work just as well and use less memory? >>> >> >> Even if I write these registers during probe, the late init check >> 'clk_core_is_enabled' would return true and would be turned OFF, that is >> the reason for marking them CRITICAL. >> > > That wouldn't happen if the clks weren't registered though, no? > I want to keep these clock CRITICAL and registered for now, but we should be able to revisit/clean them up later. -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation. --