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[79.139.233.37]) by smtp.googlemail.com with ESMTPSA id e8sm2586832ljb.45.2019.12.10.09.41.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Dec 2019 09:41:57 -0800 (PST) Subject: Re: [PATCH v3 03/15] soc: tegra: Add Tegra PMC clock registrations into PMC driver To: Sowjanya Komatineni , thierry.reding@gmail.com, jonathanh@nvidia.com, mperttunen@nvidia.com, sboyd@kernel.org, pdeschrijver@nvidia.com Cc: gregkh@linuxfoundation.org, tglx@linutronix.de, robh+dt@kernel.org, mark.rutland@arm.com, allison@lohutok.net, pgaikwad@nvidia.com, mturquette@baylibre.com, horms+renesas@verge.net.au, Jisheng.Zhang@synaptics.com, krzk@kernel.org, arnd@arndb.de, spujar@nvidia.com, josephl@nvidia.com, vidyas@nvidia.com, daniel.lezcano@linaro.org, mmaddireddy@nvidia.com, markz@nvidia.com, devicetree@vger.kernel.org, linux-clk@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, lgirdwood@gmail.com, broonie@kernel.org, perex@perex.cz, tiwai@suse.com, alexios.zavras@intel.com, alsa-devel@alsa-project.org References: <1575600535-26877-1-git-send-email-skomatineni@nvidia.com> <1575600535-26877-4-git-send-email-skomatineni@nvidia.com> <7cf4ff77-2f33-4ee5-0e09-5aa6aef3e8be@gmail.com> <288a1701-def6-d628-26bc-a305f817bdb1@gmail.com> <78644d45-2ae3-121f-99fc-0a46f205907d@nvidia.com> <49da77dc-b346-68eb-9ef8-42cfb3221489@nvidia.com> <3f1c9325-3017-62be-1e3b-82fd28540fdf@nvidia.com> From: Dmitry Osipenko Message-ID: <6fcbff3d-8695-7cd0-60de-6eb523b6964c@gmail.com> Date: Tue, 10 Dec 2019 20:41:56 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <3f1c9325-3017-62be-1e3b-82fd28540fdf@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 10.12.2019 19:53, Sowjanya Komatineni пишет: > > On 12/9/19 3:03 PM, Sowjanya Komatineni wrote: >> >> On 12/9/19 12:46 PM, Sowjanya Komatineni wrote: >>> >>> On 12/9/19 12:12 PM, Dmitry Osipenko wrote: >>>> 08.12.2019 00:36, Sowjanya Komatineni пишет: >>>>> On 12/7/19 11:59 AM, Sowjanya Komatineni wrote: >>>>>> On 12/7/19 8:00 AM, Dmitry Osipenko wrote: >>>>>>> 07.12.2019 18:53, Dmitry Osipenko пишет: >>>>>>>> 07.12.2019 18:47, Dmitry Osipenko пишет: >>>>>>>>> 07.12.2019 17:28, Dmitry Osipenko пишет: >>>>>>>>>> 06.12.2019 05:48, Sowjanya Komatineni пишет: >>>>>>>>>>> Tegra210 and prior Tegra PMC has clk_out_1, clk_out_2, clk_out_3 >>>>>>>>>>> with >>>>>>>>>>> mux and gate for each of these clocks. >>>>>>>>>>> >>>>>>>>>>> Currently these PMC clocks are registered by Tegra clock driver >>>>>>>>>>> using >>>>>>>>>>> clk_register_mux and clk_register_gate by passing PMC base >>>>>>>>>>> address >>>>>>>>>>> and register offsets and PMC programming for these clocks >>>>>>>>>>> happens >>>>>>>>>>> through direct PMC access by the clock driver. >>>>>>>>>>> >>>>>>>>>>> With this, when PMC is in secure mode any direct PMC access >>>>>>>>>>> from the >>>>>>>>>>> non-secure world does not go through and these clocks will >>>>>>>>>>> not be >>>>>>>>>>> functional. >>>>>>>>>>> >>>>>>>>>>> This patch adds these clocks registration with PMC as a clock >>>>>>>>>>> provider >>>>>>>>>>> for these clocks. clk_ops callback implementations for these >>>>>>>>>>> clocks >>>>>>>>>>> uses tegra_pmc_readl and tegra_pmc_writel which supports PMC >>>>>>>>>>> programming >>>>>>>>>>> in secure mode and non-secure mode. >>>>>>>>>>> >>>>>>>>>>> Signed-off-by: Sowjanya Komatineni >>>>>>>>>>> --- >>>>>>>>> [snip] >>>>>>>>> >>>>>>>>>>> + >>>>>>>>>>> +static const struct clk_ops pmc_clk_gate_ops = { >>>>>>>>>>> +    .is_enabled = pmc_clk_is_enabled, >>>>>>>>>>> +    .enable = pmc_clk_enable, >>>>>>>>>>> +    .disable = pmc_clk_disable, >>>>>>>>>>> +}; >>>>>>>>>> What's the benefit of separating GATE from the MUX? >>>>>>>>>> >>>>>>>>>> I think it could be a single clock. >>>>>>>>> According to TRM: >>>>>>>>> >>>>>>>>> 1. GATE and MUX are separate entities. >>>>>>>>> >>>>>>>>> 2. GATE is the parent of MUX (see PMC's CLK_OUT paths diagram >>>>>>>>> in TRM). >>>>>>>>> >>>>>>>>> 3. PMC doesn't gate EXTPERIPH clock but could "force-enable" it, >>>>>>>>> correct? >>>>> Was following existing clk-tegra-pmc as I am not sure of reason for >>>>> having these clocks registered as separate mux and gate clocks. >>>>> >>>>> Yes, PMC clocks can be registered as single clock and can use clk_ops >>>>> for set/get parent and enable/disable. >>>>> >>>>> enable/disable of PMC clocks is for force-enable to force the clock to >>>>> run regardless of ACCEPT_REQ or INVERT_REQ. >>>>> >>>>>>>> 4. clk_m_div2/4 are internal PMC OSC dividers and thus these clocks >>>>>>>> should belong to PMC. >>>>>>> Also, it should be "osc" and not "clk_m". >>>>>> I followed the same parents as it were in existing clk-tegra-pmc >>>>>> driver. >>>>>> >>>>>> Yeah they are wrong and they should be from osc and not clk_m. >>>>>> >>>>>> Will fix in next version. >>>>>> >> Reg clk_m_div2/3, they are dividers at OSC pad and not really internal >> to PMC block. >> >> current clock driver creates clk_m_div clocks which should actually be >> osc_div2/osc_div4 clocks with osc as parent. >> >> There are no clk_m_div2 and clk_m_div4 from clk_m >> >> Will fix this in next version. >> >>>> Could you please describe the full EXTPERIPH clock topology and how the >>>> pinmux configuration is related to it all? >>>> >>>> What is internal to the Tegra chip and what are the external outputs? >>>> >>>> Is it possible to bypass PMC on T30+ for the EXTPERIPH clocks? >>> >>> PMC CLK1/2/3 possible sources are OSC_DIV1, OSC_DIV2, OSC_DIV4, >>> EXTPERIPH from CAR. >>> >>> OSC_DIV1/2/4 are with internal dividers at the OSC Pads >>> >>> EXTPERIPH is from CAR and it has reset and enable controls along with >>> clock source selections to choose one of the PLLA_OUT0, CLK_S, >>> PLLP_OUT0, CLK_M, PLLE_OUT0 >>> >>> So, PMC CLK1/2/4 possible parents are OSC_DIV1, OSC_DIV2, OSC_DIV4, >>> EXTERN. >>> >>> >>> CLK1/2/3 also has Pinmux to route EXTPERIPH output on to these pins. >>> >>> >>> When EXTERN output clock is selected for these PMC clocks thru >>> CLKx_SRC_SEL, output clock is from driver by EXTPERIPH from CAR via >>> Pinmux logic or driven as per CLKx_SRC_SEL bypassing pinmux based on >>> CLKx_ACCEPT_REQ bit. >>> >>> >>> PMC Clock control register has bit CLKx_ACCEPT_REQ >>> When CLKx_ACCEPT_REQ = 0, output clock driver is from by EXTPERIPH >>> through the pinmux >>> When CLKx_ACCEPT_REQ = 1, output clock is based on CLKx_SRC_SEL bits >>> (OSC_DIV1/2/4 and EXTPERIPH clock bypassing the pinmux) >>> >>> FORCE_EN bit in PMC CLock control register forces the clock to run >>> regardless of this. > > PMC clock gate is based on the state of CLKx_ACCEPT_REQ and FORCE_EN > like explained above. > > CLKx_ACCEPT_REQ is 0 default and FORCE_EN acts as gate to enable/disable > EXTPERIPH clock output to PMC CLK_OUT_1/2/3. [and to enable OSC as well] > So I believe we need to register as MUX and Gate rather than as a single > clock. Please confirm. 1. The force-enabling is applied to both OSC and EXTERN sources of PMC_CLK_OUT_x by PMC at once. 2. Both of PMC's force-enabling and OSC/EXTERN selection is internal to PMC. Should be better to define it as a single "pmc_clk_out_x". I don't see any good reasons for differentiating PMC's Gate from the MUX, it's a single hardware unit from a point of view of the rest of the system. Peter, do you have any objections?