From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dmitry Osipenko Subject: Re: [PATCH V6 09/21] clk: tegra: clk-super: Fix to enable PLLP branches to CPU Date: Mon, 22 Jul 2019 10:17:21 +0300 Message-ID: <07897688-2a02-b7a7-7048-72c4078d26a2@gmail.com> References: <1563738060-30213-1-git-send-email-skomatineni@nvidia.com> <1563738060-30213-10-git-send-email-skomatineni@nvidia.com> <0c86cd7f-81b5-40c5-6f1e-796e8f13b522@gmail.com> <042f4b43-7b9c-533d-2548-d903b34363da@nvidia.com> <7933a83c-3208-b551-d41d-70285ae528e3@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Sowjanya Komatineni , thierry.reding@gmail.com, jonathanh@nvidia.com, tglx@linutronix.de, jason@lakedaemon.net, marc.zyngier@arm.com, linus.walleij@linaro.org, stefan@agner.ch, mark.rutland@arm.com Cc: pdeschrijver@nvidia.com, pgaikwad@nvidia.com, sboyd@kernel.org, linux-clk@vger.kernel.org, linux-gpio@vger.kernel.org, jckuo@nvidia.com, josephl@nvidia.com, talho@nvidia.com, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org, mperttunen@nvidia.com, spatra@nvidia.com, robh+dt@kernel.org, devicetree@vger.kernel.org List-Id: devicetree@vger.kernel.org 22.07.2019 10:12, Sowjanya Komatineni пишет: > > On 7/21/19 11:32 PM, Dmitry Osipenko wrote: >> 22.07.2019 6:17, Sowjanya Komatineni пишет: >>> On 7/21/19 3:39 PM, Sowjanya Komatineni wrote: >>>> On 7/21/19 2:16 PM, Dmitry Osipenko wrote: >>>>> 21.07.2019 22:40, Sowjanya Komatineni пишет: >>>>>> This patch has a fix to enable PLLP branches to CPU before changing >>>>>> the CPU clusters clock source to PLLP for Gen5 Super clock. >>>>>> >>>>>> During system suspend entry and exit, CPU source will be switched >>>>>> to PLLP and this needs PLLP branches to be enabled to CPU prior to >>>>>> the switch. >>>>>> >>>>>> On system resume, warmboot code enables PLLP branches to CPU and >>>>>> powers up the CPU with PLLP clock source. >>>>>> >>>>>> Signed-off-by: Sowjanya Komatineni >>>>>> --- >>>>>>    drivers/clk/tegra/clk-super.c            | 11 +++++++++++ >>>>>>    drivers/clk/tegra/clk-tegra-super-gen4.c |  4 ++-- >>>>>>    drivers/clk/tegra/clk.h                  |  4 ++++ >>>>>>    3 files changed, 17 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/drivers/clk/tegra/clk-super.c >>>>>> b/drivers/clk/tegra/clk-super.c >>>>>> index 39ef31b46df5..d73c587e4853 100644 >>>>>> --- a/drivers/clk/tegra/clk-super.c >>>>>> +++ b/drivers/clk/tegra/clk-super.c >>>>>> @@ -28,6 +28,9 @@ >>>>>>    #define super_state_to_src_shift(m, s) ((m->width * s)) >>>>>>    #define super_state_to_src_mask(m) (((1 << m->width) - 1)) >>>>>>    +#define CCLK_SRC_PLLP_OUT0 4 >>>>>> +#define CCLK_SRC_PLLP_OUT4 5 >>>>>> + >>>>>>    static u8 clk_super_get_parent(struct clk_hw *hw) >>>>>>    { >>>>>>        struct tegra_clk_super_mux *mux = to_clk_super_mux(hw); >>>>>> @@ -97,6 +100,14 @@ static int clk_super_set_parent(struct clk_hw >>>>>> *hw, u8 index) >>>>>>            if (index == mux->div2_index) >>>>>>                index = mux->pllx_index; >>>>>>        } >>>>>> + >>>>>> +    /* >>>>>> +     * Enable PLLP branches to CPU before selecting PLLP source >>>>>> +     */ >>>>>> +    if ((mux->flags & TEGRA_CPU_CLK) && >>>>>> +        ((index == CCLK_SRC_PLLP_OUT0) || (index == >>>>>> CCLK_SRC_PLLP_OUT4))) >>>>>> +        tegra_clk_set_pllp_out_cpu(true); >>>>> Should somewhere here be tegra_clk_set_pllp_out_cpu(false) when >>>>> switching from PLLP? >>>> PLLP may be used for other CPU clusters. >>> Though to avoid flag and check needed to make sure other CPU is not >>> using before disabling PLLP branch to CPU. >>> >>> But leaving it enabled shouldn't impact much as clock source mux is >>> after this in design anyway. >>> >>> But can add as well if its clear that way. >> The TRM doc says "The CPU subsystem supports a switch-cluster mode >> meaning that only one of the clusters can be active at any given time". >> >> Given that cluster-switching isn't supported in upstream, I don't think >> that you need to care about the other cluster at all, at least for now. >> >> The cluster-switching implementation in upstream is very complicated >> because it requires a special "hotplugging" CPU governor, which >> apparently no other platform needs. >> >> [snip] > > This patch enables PLLP branches to CPU for both CPUG & CPULP if they > use PLLP source. > > So, to disable PLLP out CPU when not in use, we still need check for > other cluster because during resume both LP CPU and G CPU gets restored. > CPUG runs from PLLP on resume and when it does super clk restore for LP > CPU which may not be using PLLP, but as both uses same super mux > clk_ops, without check (for PLLP branch to CPU in use) disabling PLLP > branch to CPU during LP CPU restore looses clock to CPU G as well which > is running from PLLP. > > Will add check and disable PLLP if not in use in next version... this > need extern flag as well to mark PLLP usage with either of CPU's. I still don't understand why do you need to care about LP cluster at all, given that it's always in a power-gated state.