From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jon Hunter Subject: Re: [PATCH v3 09/11] cpufreq: tegra124-cpufreq: extend to support Tegra210 Date: Tue, 13 Mar 2018 10:20:52 +0000 Message-ID: References: <1517934852-23255-1-git-send-email-pdeschrijver@nvidia.com> <1517934852-23255-10-git-send-email-pdeschrijver@nvidia.com> <85edea04-6aaf-3609-1da9-0d542ac98e7d@nvidia.com> <20180313095117.GX6190@tbergstrom-lnx.Nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180313095117.GX6190@tbergstrom-lnx.Nvidia.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Peter De Schrijver Cc: linux-tegra@vger.kernel.org, linux-clk@vger.kernel.org, mturquette@baylibre.com, sboyd@codeaurora.org, robh+dt@kernel.org, mark.rutland@arm.com, devicetree@vger.kernel.org, lgirdwood@gmail.com, broonie@kernel.org, linux-kernel@vger.kernel.org List-Id: devicetree@vger.kernel.org On 13/03/18 09:51, Peter De Schrijver wrote: > On Mon, Mar 12, 2018 at 12:15:22PM +0000, Jon Hunter wrote: >> >> On 06/02/18 16:34, Peter De Schrijver wrote: >>> Tegra210 has a very similar CPU clocking scheme than Tegra124. So add >>> support in this driver. Also allow for the case where the CPU voltage is >>> controlled directly by the DFLL rather than by a separate regulator object. >>> >>> Signed-off-by: Peter De Schrijver >>> --- >>> drivers/cpufreq/tegra124-cpufreq.c | 15 ++++++++------- >>> 1 file changed, 8 insertions(+), 7 deletions(-) >>> >>> diff --git a/drivers/cpufreq/tegra124-cpufreq.c b/drivers/cpufreq/tegra124-cpufreq.c >>> index 4353025..f8e01a8 100644 >>> --- a/drivers/cpufreq/tegra124-cpufreq.c >>> +++ b/drivers/cpufreq/tegra124-cpufreq.c >>> @@ -64,7 +64,8 @@ static void tegra124_cpu_switch_to_pllx(struct tegra124_cpufreq_priv *priv) >>> { >>> clk_set_parent(priv->cpu_clk, priv->pllp_clk); >>> clk_disable_unprepare(priv->dfll_clk); >>> - regulator_sync_voltage(priv->vdd_cpu_reg); >>> + if (priv->vdd_cpu_reg) >>> + regulator_sync_voltage(priv->vdd_cpu_reg); >>> clk_set_parent(priv->cpu_clk, priv->pllx_clk); >>> } >> >> OK, so this bit does not make sense to me. In the above we are switching >> from the DFLL to the PLL (ie. disabling the DFLL) and so to ensure we >> are operating at the correct voltage after disabling the DFLL we need to >> sync the voltage. Seems we would need to do this for all devices, no? >> How is the different between Tegra124 and Tegra210? > > Yes. So in case of i2c the regulator framework will reapply the voltage it > knows which in our case is the boot voltage for VDD_CPU because noone else > from a regulator framework pov has ever changed the voltage. In case of PWM > putting the PWM output pad in tri state will cause the OVR regulator to output > a hardware defined voltage. This is done as part of the dfll_clk_disable() > function. To summarize: So this is the piece of information I was missing. Maybe add this to the changelog so it is clear why we do not need to handle the cpu rail in the case of PWM. Cheers Jon -- nvpublic