Date:   Mon, 9 Sep 2019 11:32:47 -0500
From:   Adam Ford <aford173@...il.com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     André Roth <neolynx@...il.com>,
        Linux-OMAP <linux-omap@...r.kernel.org>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andreas Kemnade <andreas@...nade.info>,
        Tony Lindgren <tony@...mide.com>
Subject: Re: [Letux-kernel] [RFC PATCH 0/3] Enable 1GHz support on omap36xx

On Mon, Sep 9, 2019 at 11:20 AM Adam Ford <aford173@...il.com> wrote:
>
> On Mon, Sep 9, 2019 at 9:57 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
> >
> > Hi Adam,
> >
> > > Am 09.09.2019 um 16:26 schrieb Adam Ford <aford173@...il.com>:
> > >
> > > On Sat, Sep 7, 2019 at 2:38 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
> > >>
> > >> Hi Adam,
> > >>
> > >>> Am 02.09.2019 um 23:10 schrieb Adam Ford <aford173@...il.com>:
> > >>>
> > >>> On Mon, Sep 2, 2019 at 10:46 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
> > >>>>
> > >>>>
> > >>>>
> > >>>> But my tests show that decoding works now. So you already might give it a try.
> > >>>
> > >>> I am traveling all this week, but I have an omap3530, DM3730
> > >>> (omap3630), and an AM3517 that I use for testing.
> > >>
> > >> now as the omap3430 and omap3630 opp-v2 tables are installed,
> > >> we could add am35x7 as well.
> > >>
> > >> What needs to be done:
> > >>
> > >> 1. add OPP-v2 table to am3517.dtsi
> > >>
> > >> for example copy skeleton from omap36xx.dtsi
> > >>
> > >> and define reasonable clock speeds. I would think about
> > >> 150 MHz, 300 MHz, 600MHz.
> > >
> > > This might be more of a question for TI, but  can we match the 3430
> > > list of frequencies?
> > >
> > > Something like:
> > >    125000  1200000
> > >    250000  1200000
> > >    500000  1200000
> > >    550000  1200000
> > >    600000  1200000
> >
> > And another question: is it more derived from omap3430 or omap3630?
> >
> > >
> > >
> > >>
> > >> Debatable is if we need a clock-latency definition.
> > >>
> > >> 2. change all voltages to 1.2V
> > >>
> > >>                        opp-microvolt = <1200000 1200000 1200000>;
> > >>
> > >> There is no point to specify 3 voltages <target min max> here since we
> > >> will never need a min and a max value.
> > >>
> > >>                        opp-microvolt = <1200000>;
> > >>
> > >> should also be ok (AFAIK, parser handles single-value records).
> > >>
> > >> 3. AFAIK there is no speed binned eFuse...
> > >>
> > >> But the ti-cpufreq driver always wants to read some eFuse register.
> > >>
> > >> So please check if you can read 0x4800244C and 0x4830A204
> > >> like on omap36xx and if they produce stable values (and not
> > >> random noise).
> > >
> > > For the AM3517,
> > >
> > > 0x4800244C = 0000 0cc0
> >
> > If it behaves like an dm3730 (Table 1-6) this would be read as 800/600MHz
> > and some reserved code in bit 7:6.
> >
> > If it behaves like an omap3530 (Table 1-6) this would bean 600MHz but reserved
> > value for IVA Frequency.
> >
> >
> > > 0x4830A204 = 1b86 802f
> >
> > would be decoded (Table 1-7) as "AM/DM37x ES1.1"
> >
> > omap35xx would have a different code (Table 1-9). Most similar is "OMAP35x ES2.0" with 0x1B7A E02F
> >
> > So this seems to answer that the am3517 is indeed a derivative of the am/dm37xx.
> >
> > Therefore the only OPPs would be OPP50 (300 MHz) and OPP100 (600 MHz).
> >
> > Only tests or TI internal documentations could show if the am3517 still
> > runs stable at newly invented "OPP25" (150MHz).
> >
> > >
> > > The AM3517 shows these are valid addresses and I read them multiple
> > > times and they yielded the same results even after power cycling.
> > >
> > >
> > >>
> > >> If yes, we simply assume that am3517 is similar enough to omap3630,
> > >> ignore that there is no eFuse, but read the register anyways and
> > >> then ignore the bit if it is 0 or 1.
> > >>
> > >> This means that all OPPs can get
> > >>
> > >>                        opp-supported-hw = <0xffffffff 0xffffffff>;
> > >>
> > >> There could also be a default handler if this property is missing,
> > >> but I have not researched this.
> > >>
> > > Like this?
> > >
> > > opp1-125000000 {
> > >     opp-hz = /bits/ 64 <125000000>;
> > >     opp-microvolt = <1200000>;
> > >     opp-supported-hw = <0xffffffff 0xffffffff>;
> > > };
> > >
> > > opp2-250000000 {
> > >     opp-hz = /bits/ 64 <250000000>;
> > >     opp-microvolt = <1200000>;
> > >    opp-supported-hw = <0xffffffff 0xffffffff>;
> > >     opp-suspend;
> > > };
> > >
> > > opp3-500000000 {
> > >     opp-hz = /bits/ 64 <500000000>;
> > >     opp-microvolt = <1200000>;
> > >     opp-supported-hw = <0xffffffff 0xffffffff>;
> > > };
> > >
> > > opp4-550000000 {
> > >     opp-hz = /bits/ 64 <550000000>;
> > >     opp-microvolt = <1200000>;
> > >     opp-supported-hw = <0xffffffff 0xffffffff>;
> > > };
> > >
> > > opp5-600000000 {
> > >     opp-hz = /bits/ 64 <600000000>;
> > >     opp-microvolt = <1200000>;
> > >     opp-supported-hw = <0xffffffff 0xffffffff>;
> > > };
> >
> > Yes.
> >
> > >
> > > What does opp-suspend do?  I noticed it in the 34xx.dtsi
> >
> > Good question. I think it is the OPP to be chosen before suspend:
> >
> > https://www.kernel.org/doc/Documentation/devicetree/bindings/opp/opp.txt
> > says
> >
> > - opp-suspend: Marks the OPP to be used during device suspend. Only one OPP in
> >   the table should have this.
> >
> > But that doesn't mean the drivers make use of this marker.
> >
> > This makes me also wonder if we should tag the OPP1G and OPP6 as "turbo-mode"...
> >
> > Another question that came up by private mail from André was if we
> > should better disable the turbo OPPs of omap34xx and 36xx by default
> > (status = "disabled";) because there are concerns about overheating
> > the chips and we have no thermal regulation like for omap4 & 5.
> >
> > But this would mean that every board DTS would have to set it explicitly
> > to "enabled".
> >
> > And another concern is if the 1GHz OPP doesn't also need to switch the
> > ABB bias LDO to a different mode. This is not done by the ti-cpufreq driver.
> > Maybe it is done by some driver in mach-omap but I have not searched for.
>
> ti-omap5-opp-supply.txt shows
>
> Required Properties for Device Node:
> - vdd-supply: phandle to regulator controlling VDD supply
> - vbb-supply: phandle to regulator controlling Body Bias supply
>       (Usually Adaptive Body Bias regulator)
>
> Looking at the ti-cpufreq.c driver, it appears as if there is both a
> vdd and a vbb listed in the table (line 302).  AFAICT, we should be
> able to just set it up pointing VDD to the PMIC and VBB at the ABB
> unless I am missing something.
>
> Currently, I have the follwing in my device tree:
>
> /* Reroute power feeding the CPU to come from the external PMIC */
> &reg_arm
> {
>      vin-supply = <&sw1a_reg>;
> };
>
> &reg_soc
> {
>       vin-supply = <&sw1c_reg>;
> };
>
Ignore that.  (wrong board)
Correction,

cpus {
     cpu@0 {
          cpu0-supply = <&vcc>;
     };
};

I had too many boards.
> Is this still correct with the new cpufreq driver?   I am wondering if
> we need VDD and VBB references under the cpu entry.  The
> ti-omap5-opp-supply ready me also reads:
>
> /* Device Node (CPU)  */
> cpus {
>      cpu0: cpu@0 {
>           device_type = "cpu";
>
> ...
>
>           vdd-supply = <&vcc>;
>           vbb-supply = <&abb_mpu>;
>      };
> };
>
> This isn't in the ti-cpufreq.txt, however it might actually be
> utilized based on a quick skim of the driver.
>
> adam
> >
> > So the concern is that we will run the turbo modes outside of the TI specs
> > while before applying the patch set this would be a lesser problem (OPP130
> > should also be thermally limited to 90°C).
> >
> > I.e. users of 1GHz capable boards will not only see 25% more speed but
> > suddenly higher SoC temperatures than the years before.
> >
> > >
> > >> 4. add compatible to ti-cpufreq
> > >> and share the register offsets, bit masks etc. with omap3630:
> > >>
> > >>        { .compatible = "ti,am33xx", .data = &am3x_soc_data, },
> > >>        { .compatible = "ti,am3517", .data = &omap36xx_soc_data, },
> > >>        { .compatible = "ti,am43", .data = &am4x_soc_data, },
> > >>        { .compatible = "ti,dra7", .data = &dra7_soc_data },
> > >>        { .compatible = "ti,omap3430", .data = &omap34xx_soc_data, },
> > >>        { .compatible = "ti,omap3630", .data = &omap36xx_soc_data, },
> > >>
> > >> 5. configure for CONFIG_ARM_TI_CPUFREQ=y
> > >>
> > >> This should IMHO suffice.
> > >
> > > If you're OK with what I am proposing, I'll run some tests and submit
> > > a patch.  I won't promise to fully understand what's happening.  :-)
> >
> > Same for me :)
> >
> > BR and thanks,
> > Nikolaus
> >

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