Date:   Mon, 2 Dec 2019 10:47:49 -0800
From:   Sowjanya Komatineni <skomatineni@...dia.com>
To:     Dmitry Osipenko <digetx@...il.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <mperttunen@...dia.com>, <sboyd@...nel.org>
CC:     <gregkh@...uxfoundation.org>, <tglx@...utronix.de>,
        <robh+dt@...nel.org>, <mark.rutland@....com>,
        <allison@...utok.net>, <pdeschrijver@...dia.com>,
        <pgaikwad@...dia.com>, <mturquette@...libre.com>,
        <horms+renesas@...ge.net.au>, <Jisheng.Zhang@...aptics.com>,
        <krzk@...nel.org>, <arnd@...db.de>, <spujar@...dia.com>,
        <josephl@...dia.com>, <vidyas@...dia.com>,
        <daniel.lezcano@...aro.org>, <mmaddireddy@...dia.com>,
        <markz@...dia.com>, <devicetree@...r.kernel.org>,
        <linux-clk@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 00/11] Move PMC clocks into Tegra PMC driver


On 11/28/19 5:06 AM, Dmitry Osipenko wrote:
> 28.11.2019 00:38, Sowjanya Komatineni пишет:
>> On 11/27/19 9:02 AM, Sowjanya Komatineni wrote:
>>> On 11/27/19 6:31 AM, Dmitry Osipenko wrote:
>>>> 27.11.2019 07:59, Sowjanya Komatineni пишет:
>>>>> Tegra PMC has clk_out_1, clk_out_2, clk_out_3 and blink controls which
>>>>> are currently registered by Tegra clock driver using clk_regiser_mux
>>>>> and
>>>>> clk_register_gate which performs direct Tegra PMC register access.
>>>>>
>>>>> When Tegra PMC is in secure mode, any access from non-secure world will
>>>>> not go through.
>>>>>
>>>>> This patch series adds these Tegra PMC clocks and blink controls to
>>>>> Tegra
>>>>> PMC driver with PMC as clock provider and removed them from Tegra clock
>>>>> driver. This also adds PMC specific clock id's to use in device tree
>>>>> and
>>>>> removed clock ids of PMC clock from Tegra clock driver.
>>>>>
>>>>> This series also includes patch to update clock provider from tegra_car
>>>>> to pmc in the device tree tegra210-smaug.dts that uses clk_out_2
>>>>> from PMC.
>>>>>
>>>>> [v2]:    Changes between v1 and v2 are
>>>>>      - v2 includes patches for adding clk_out_1, clk_out_2, clk_out_3,
>>>>>        blink controls to Tegra PMC driver and removing clk-tegra-pmc.
>>>>>      - feedback related to pmc clocks in Tegra PMC driver from v1
>>>>>      - Removed patches for WB0 PLLM overrides and PLLE IDDQ PMC
>>>>> programming
>>>>>        by the clock driver using helper functions from Tegra PMC.
>>>>>
>>>>>          Note:
>>>>>        To use helper functions from PMC driver, PMC early init need to
>>>>>        happen prior to using helper functions and these helper
>>>>> functions are
>>>>>        for PLLM Override and PLLE IDDQ programming in PMC during
>>>>> PLLM/PLLE
>>>>>        clock registration which happen in clock_init prior to Tegra PMC
>>>>>        probe.
>>>>>        Moving PLLM/PLLE clocks registration to happen after Tegra PMC
>>>>>        impacts other clocks EMC, MC and corresponding tegra_emc_init and
>>>>>        tegra_mc_init.
>>>>>        This implementation of configuring PMC registers thru helper
>>>>>        functions in clock driver needs proper changes across PMC, Clock,
>>>>>        EMC and MC inits to have it work across all Tegra platforms.
>>>>>
>>>>>        Currently PLLM Override is not enabled in the bootloader so
>>>>> proper
>>>>>        patches for this fix will be taken care separately.
>>>> Hello Sowjanya,
>>>>
>>>> Could you please clarify what do you mean by "PLLM Override not enabled
>>>> in bootloader"?
>>>>
>>>> There is T124 Nyan Big Chromebook which is supported in upstream kernel,
>>>> it has PLLM Override set by bootloader. I also have T30 Nexus 7 tablet
>>>> which has the PLLM Override set by bootloader as well. It's not clear to
>>>> me whether this patch series is supposed to break these devices. If the
>>>> breakage is the case here, then I'm afraid you can't postpone supporting
>>>> the PLLM Override and a full-featured implementation is needed.
>>> Hi Dmitry,
>>>
>>> Secure boot currently is enabled only on Tegra210 and Tegra210
>>> bootloader doesn't enable PLLM override.
>>>
>>> So PLLM override/PLLE IDDQ being in clock driver currently will not
>>> break on any of existing Tegra platforms.
>>>
>>>> I briefly tried to test this series on T30 and this time it doesn't hang
>>>> on boot, but somehow WiFi MMC card detection is broken. AFAIK, the WiFi
>>>> chip uses the Blink clock source and the clock should be enabled by the
>>>> MMC core because this is how DT part looks like:
>>>>
>>>> brcm_wifi_pwrseq: wifi-pwrseq {
>>>>      compatible = "mmc-pwrseq-simple";
>>>>      clocks = <&pmc TEGRA_PMC_CLK_BLINK>;
>>>>      clock-names = "ext_clock";
>>>>      reset-gpios =  <&gpio TEGRA_GPIO(D, 3) GPIO_ACTIVE_LOW>;
>>>>      post-power-on-delay-ms = <300>;
>>>>      power-off-delay-us = <300>;
>>>> };
>>>>
>>>> BTW, I  tried this series on a T20 device which also uses the Blink
>>>> clock for WiFi card and it works. So looks like this patchset has some
>>>> problem in regards to the T30 PMC clocks implementation.
>>>>
>>>> [snip]
>>> Blink init state is set to true for both Tegra20 and Tegra30 and all
>>> go through the same blink programming sequence.
>>>
>>> Will try to add more debug messages to dump registers and will test
>>> blink through device tree on T30 and will get back...
>>>
>>>
>> define value for BLINK uses BIT macro instead of just position. Will fix
>> this in v3.
> Thanks, will try v3 once it will be ready.
>
> I took a look through the T20 board's schematics and seems it doesn't
> use the Blink clock for the WiFi, instead it uses 32k source directly
> from PMU. While T30 board schematics tells that  32k comes out from the
> Tegra chip.
>
> BTW, I'm curious what's the reason for having Blink clock always-ON on
> T20/30, any insights? Looks like it's just some relic from old clk
> driver and it should be safe to drop the always-ON.

T30 cardhu uses 32K from Tegra to WIFI but its only needed to be on 
during WIFI power up sequence and not required to be on during boot.

I had it enabled as existing clock driver enables it default and dont 
want to break things if it was left ON intentionally.

Peter/Thierry, Any reason 32K from Blink is enabled to be ON during 
clock init for T20/T30 in clock-tegra-pmc driver?

Based on the design T30 uses this for WIFI and WIFI driver should be 
handling this clock enable/disable during power up/down sequence,

so we don't have to enable it default during boot right?

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