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 10:30:01 +0300 Message-ID: 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> <07897688-2a02-b7a7-7048-72c4078d26a2@gmail.com> <90e1a90b-1d33-a5db-9af8-dc5c5d45b65f@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <90e1a90b-1d33-a5db-9af8-dc5c5d45b65f@nvidia.com> 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 10:24, Sowjanya Komatineni пишет: > > On 7/22/19 12:17 AM, Dmitry Osipenko wrote: >> 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. > > cclk_lp is registered thru super clk mux which uses same clk_ops as cclk_g. > > during restore, cclk_lp also gets restored. So both cclk_lp & cclk_g > goes thru same clk_ops > > In this patch, I marked super flags with TEGRA_CPU_CLK for both cclk_lp > & cclk_g. > > So when cclk_lp restore happens, it goes thru same set_parent clk_ops > and as its source is not PLLP, it tries to disable PLLP_OUT_CPU if its > disabled without adding check for PLLP being in use by other cluster. Ah, okay. > So either I should not mark cclk_lp as TEGRA_CPU_CLK and mark cclk_g > only as TEGRA_CPU_CLK so PLLP out to CPU can be disabled without check > if its not the source. > > OR > > With TEGRA_CPU_CLK used for both cclk_lp & cclk_g, need to add check if > PLLP is in use so during cclk_lp restore it doesnt disable PLLP out to CPU. > > > To simplify without check, will just mark cclk_g super clock flag only > as TEGRA_CPU_CLK so PLLP_OUT_CPU enable or disable happens only for CPUG Sounds good. Then please add a brief comment to the CPULP, telling why it misses the flag, for the record.