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

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Message-Id: <12A8E9DF-3D58-48A7-BC91-898B21536E04@goldelico.com>
Date:   Sat, 7 Sep 2019 08:34:14 +0200
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Tony Lindgren <tony@...mide.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-pm@...r.kernel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        André Roth <neolynx@...il.com>,
        Benoît Cousson <bcousson@...libre.com>,
        kernel@...a-handheld.com, Linux-OMAP <linux-omap@...r.kernel.org>,
        Adam Ford <aford173@...il.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>
Subject: Re: [RFC v2 1/3] cpufreq: ti-cpufreq: add support for omap34xx and omap36xx


> Am 06.09.2019 um 22:46 schrieb H. Nikolaus Schaller <hns@...delico.com>:
> 
> Hi,
> 
>> Am 06.09.2019 um 05:01 schrieb Viresh Kumar <viresh.kumar@...aro.org>:
>> 
>> On 05-09-19, 07:32, Tony Lindgren wrote:
>>> * H. Nikolaus Schaller <hns@...delico.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@...04:~# 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@...04:~# 
> 
>> 
>>> 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.

The OPP is now available. Only

[    2.569519] omap2_set_init_voltage: unable to find boot up OPP for vdd_core

remains but this is a different issue (mismatch between U-Boot clock/vdd_core
setup and kernel table). Most likely U-Boot runs with an 300MHz OPP which is
not defined by data sheet or kernel opp tables.

BR,
Nikolaus