Re: [RFC v2 1/3] cpufreq: ti-cpufreq: add support for omap34xx and omap36xx

From: "H. Nikolaus Schaller" <hns@goldelico.com>
To: Viresh Kumar <viresh.kumar@linaro.org>, Tony Lindgren <tony@atomide.com>
Cc: "Benoît Cousson" <bcousson@baylibre.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Adam Ford" <aford173@gmail.com>,
	"André Roth" <neolynx@gmail.com>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Linux-OMAP <linux-omap@vger.kernel.org>,
	devicetree <devicetree@vger.kernel.org>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	linux-pm@vger.kernel.org,
	"Discussions about the Letux Kernel"
	<letux-kernel@openphoenux.org>,
	kernel@pyra-handheld.com
Subject: Re: [RFC v2 1/3] cpufreq: ti-cpufreq: add support for omap34xx and omap36xx
Date: Fri, 6 Sep 2019 22:46:49 +0200	[thread overview]
Message-ID: <1ED2450A-A445-42B8-8956-58A53F15DBE2@goldelico.com> (raw)
In-Reply-To: <20190906030158.leuumg7rwsvowwfx@vireshk-i7>

Hi,

> Am 06.09.2019 um 05:01 schrieb Viresh Kumar <viresh.kumar@linaro.org>:
> 
> On 05-09-19, 07:32, Tony Lindgren wrote:
>> * H. Nikolaus Schaller <hns@goldelico.com> [190904 08:54]:
>>> This adds code and tables to read the silicon revision and
>>> eFuse (speed binned / 720 MHz grade) bits for selecting
>>> opp-v2 table entries.
>>> 
>>> Since these bits are not always part of the syscon register
>>> range (like for am33xx, am43, dra7), we add code to directly
>>> read the register values using ioremap() if syscon access fails.
>> 
>> This is nice :) Seems to work for me based on a quick test
>> on at least omap36xx.
>> 
>> Looks like n900 produces the following though:
>> 
>> core: _opp_supported_by_regulators: OPP minuV: 1270000 maxuV: 1270000, not supported by regulator
>> cpu cpu0: _opp_add: OPP not supported by regulators (550000000)
> 
> That's a DT thing I believe where the voltage doesn't fit what the
> regulator can support.

I can confirm this on BeagleBoard C2:

root@gta04:~# dmesg|fgrep -i opp
[    2.347442] core: _opp_supported_by_regulators: OPP minuV: 1270000 maxuV: 1270000, not supported by regulator
[    2.359222] cpu cpu0: _opp_add: OPP not supported by regulators (550000000)
[    2.580993] omap2_set_init_voltage: unable to find boot up OPP for vdd_core
root@gta04:~# 

> 
>> But presumably that can be further patched.

Well, the opp-v1 table also has this voltage point:

			/* OMAP343x/OMAP35xx variants OPP1-5 */
			operating-points = <
				/* kHz    uV */
				125000   975000
				250000  1075000
				500000  1200000
				550000  1270000
				600000  1350000
			>;

This is OPP4 which is recommended by OMAP3530 data sheet to be 1.27V +/- 5%

Data sheet of tps65950 says

	• VDD1: 1.2-A, buck DC/DC converter (VOUT = 0.6 V to 1.45 V, in steps of 12.5 mV)

This means 1270 mV is not a "step" and rejected by the twl4030 driver.
Maybe nobody did notice yet because the opp-v1 drivers did not warn...

The closest value to 1.27V is 0.6V + 54 * 12.5mV is 1.275V

So let's also change the OPP4 to 1275000 uV in the opp-v2 table.

BR and thanks,
Nikolaus