From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sowjanya Komatineni Subject: Re: [PATCH v8 11/21] clk: tegra: clk-dfll: Add suspend and resume support Date: Fri, 9 Aug 2019 11:33:26 -0700 Message-ID: <9902aa72-3f18-9840-35ad-137293d2e26c@nvidia.com> References: <1565308020-31952-1-git-send-email-skomatineni@nvidia.com> <1565308020-31952-12-git-send-email-skomatineni@nvidia.com> <29a85a35-10ff-2d43-d148-9dba1ee25869@nvidia.com> <84a0d46a-bca2-1000-a2a6-8890ee702dd3@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <84a0d46a-bca2-1000-a2a6-8890ee702dd3@gmail.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Dmitry Osipenko , 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, rjw@rjwysocki.net, viresh.kumar@linaro.org, linux-pm@vger.kernel.org List-Id: devicetree@vger.kernel.org On 8/9/19 11:00 AM, Dmitry Osipenko wrote: > 09.08.2019 19:39, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> On 8/9/19 5:23 AM, Dmitry Osipenko wrote: >>> 09.08.2019 2:46, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>> This patch implements DFLL suspend and resume operation. >>>> >>>> During system suspend entry, CPU clock will switch CPU to safe >>>> clock source of PLLP and disables DFLL clock output. >>>> >>>> DFLL driver suspend confirms DFLL disable state and errors out on >>>> being active. >>>> >>>> DFLL is re-initialized during the DFLL driver resume as it goes >>>> through complete reset during suspend entry. >>>> >>>> Signed-off-by: Sowjanya Komatineni >>>> --- >>>> =C2=A0 drivers/clk/tegra/clk-dfll.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 56 ++++++++++++++++++= ++++++++++++ >>>> =C2=A0 drivers/clk/tegra/clk-dfll.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |=C2=A0 2 ++ >>>> =C2=A0 drivers/clk/tegra/clk-tegra124-dfll-fcpu.c |=C2=A0 1 + >>>> =C2=A0 3 files changed, 59 insertions(+) >>>> >>>> diff --git a/drivers/clk/tegra/clk-dfll.c b/drivers/clk/tegra/clk-dfll= .c >>>> index f8688c2ddf1a..eb298a5d7be9 100644 >>>> --- a/drivers/clk/tegra/clk-dfll.c >>>> +++ b/drivers/clk/tegra/clk-dfll.c >>>> @@ -1487,6 +1487,7 @@ static int dfll_init(struct tegra_dfll *td) >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 td->last_unrounded_rate =3D 0; >>>> =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pm_runtime_enable(td->dev); >>>> +=C2=A0=C2=A0=C2=A0 pm_runtime_irq_safe(td->dev); >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pm_runtime_get_sync(td->dev); >>>> =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 dfll_set_mode(td, DFLL_DISABLED= ); >>>> @@ -1513,6 +1514,61 @@ static int dfll_init(struct tegra_dfll *td) >>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return ret; >>>> =C2=A0 } >>>> =C2=A0 +/** >>>> + * tegra_dfll_suspend - check DFLL is disabled >>>> + * @dev: DFLL device * >>>> + * >>>> + * DFLL clock should be disabled by the CPUFreq driver. So, make >>>> + * sure it is disabled and disable all clocks needed by the DFLL. >>>> + */ >>>> +int tegra_dfll_suspend(struct device *dev) >>>> +{ >>>> +=C2=A0=C2=A0=C2=A0 struct tegra_dfll *td =3D dev_get_drvdata(dev); >>>> + >>>> +=C2=A0=C2=A0=C2=A0 if (dfll_is_running(td)) { >>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 dev_err(td->dev, "dfll is = enabled while shouldn't be\n"); >>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return -EBUSY; >>>> +=C2=A0=C2=A0=C2=A0 } >>>> + >>>> +=C2=A0=C2=A0=C2=A0 reset_control_assert(td->dvco_rst); >>>> + >>>> +=C2=A0=C2=A0=C2=A0 return 0; >>>> +} >>>> +EXPORT_SYMBOL(tegra_dfll_suspend); >>>> + >>>> +/** >>>> + * tegra_dfll_resume - reinitialize DFLL on resume >>>> + * @dev: DFLL instance >>>> + * >>>> + * DFLL is disabled and reset during suspend and resume. >>>> + * So, reinitialize the DFLL IP block back for use. >>>> + * DFLL clock is enabled later in closed loop mode by CPUFreq >>>> + * driver before switching its clock source to DFLL output. >>>> + */ >>>> +int tegra_dfll_resume(struct device *dev) >>>> +{ >>>> +=C2=A0=C2=A0=C2=A0 struct tegra_dfll *td =3D dev_get_drvdata(dev); >>>> + >>>> +=C2=A0=C2=A0=C2=A0 reset_control_deassert(td->dvco_rst); >>> This doesn't look right because I assume that DFLL resetting is >>> synchronous and thus clk should be enabled in order for reset to >>> propagate inside hardware. >>> >>>> +=C2=A0=C2=A0=C2=A0 pm_runtime_get_sync(td->dev); >>> Hence it will be better to remove the above reset_control_deassert() an= d >>> add here: >>> >>> =C2=A0=C2=A0=C2=A0=C2=A0reset_control_reset(td->dvco_rst); >> By the time dfll resume happens, dfll controller clock will already be e= nabled. >> >> so doing reset de-assert before pm_runtime seems ok. > I don't see what enables the DFLL clock because it should be enabled by t= he CPUFreq driver > on resume from suspend and resume happens after resuming of the DFLL driv= er. dvco_rst is part of peripheral clocks and all peripheral clocks are=20 restored by clk-tegra210 driver which happens before dfll driver resume. So dfll rst thru part of peripheral clock enable is set prior to dfll=20 reset deassertion