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Subject: Re: [PATCH v3 03/15] soc: tegra: Add Tegra PMC clock registrations
 into PMC driver
To:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        thierry.reding@gmail.com, jonathanh@nvidia.com,
        mperttunen@nvidia.com, sboyd@kernel.org, pdeschrijver@nvidia.com
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From:   Dmitry Osipenko <digetx@gmail.com>
Message-ID: <2ec3c1f1-228d-31a6-a432-fd39e91b2baa@gmail.com>
Date:   Fri, 13 Dec 2019 01:13:43 +0300
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12.12.2019 06:54, Sowjanya Komatineni пишет:
> 
> On 12/11/19 7:45 PM, Sowjanya Komatineni wrote:
>>
>> On 12/11/19 5:39 PM, Dmitry Osipenko wrote:
>>> 11.12.2019 21:50, Sowjanya Komatineni пишет:
>>>> On 12/10/19 5:06 PM, Sowjanya Komatineni wrote:
>>>>> On 12/10/19 9:41 AM, Dmitry Osipenko wrote:
>>>>>> 10.12.2019 19:53, Sowjanya Komatineni пишет:
>>>>>>> On 12/9/19 3:03 PM, Sowjanya Komatineni wrote:
>>>>>>>> On 12/9/19 12:46 PM, Sowjanya Komatineni wrote:
>>>>>>>>> On 12/9/19 12:12 PM, Dmitry Osipenko wrote:
>>>>>>>>>> 08.12.2019 00:36, Sowjanya Komatineni пишет:
>>>>>>>>>>> On 12/7/19 11:59 AM, Sowjanya Komatineni wrote:
>>>>>>>>>>>> On 12/7/19 8:00 AM, Dmitry Osipenko wrote:
>>>>>>>>>>>>> 07.12.2019 18:53, Dmitry Osipenko пишет:
>>>>>>>>>>>>>> 07.12.2019 18:47, Dmitry Osipenko пишет:
>>>>>>>>>>>>>>> 07.12.2019 17:28, Dmitry Osipenko пишет:
>>>>>>>>>>>>>>>> 06.12.2019 05:48, Sowjanya Komatineni пишет:
>>>>>>>>>>>>>>>>> Tegra210 and prior Tegra PMC has clk_out_1, clk_out_2,
>>>>>>>>>>>>>>>>> clk_out_3
>>>>>>>>>>>>>>>>> with
>>>>>>>>>>>>>>>>> mux and gate for each of these clocks.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Currently these PMC clocks are registered by Tegra clock
>>>>>>>>>>>>>>>>> driver
>>>>>>>>>>>>>>>>> using
>>>>>>>>>>>>>>>>> clk_register_mux and clk_register_gate by passing PMC base
>>>>>>>>>>>>>>>>> address
>>>>>>>>>>>>>>>>> and register offsets and PMC programming for these clocks
>>>>>>>>>>>>>>>>> happens
>>>>>>>>>>>>>>>>> through direct PMC access by the clock driver.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> With this, when PMC is in secure mode any direct PMC
>>>>>>>>>>>>>>>>> access
>>>>>>>>>>>>>>>>> from the
>>>>>>>>>>>>>>>>> non-secure world does not go through and these clocks will
>>>>>>>>>>>>>>>>> not be
>>>>>>>>>>>>>>>>> functional.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> This patch adds these clocks registration with PMC as a
>>>>>>>>>>>>>>>>> clock
>>>>>>>>>>>>>>>>> provider
>>>>>>>>>>>>>>>>> for these clocks. clk_ops callback implementations for
>>>>>>>>>>>>>>>>> these
>>>>>>>>>>>>>>>>> clocks
>>>>>>>>>>>>>>>>> uses tegra_pmc_readl and tegra_pmc_writel which
>>>>>>>>>>>>>>>>> supports PMC
>>>>>>>>>>>>>>>>> programming
>>>>>>>>>>>>>>>>> in secure mode and non-secure mode.
>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> Signed-off-by: Sowjanya Komatineni
>>>>>>>>>>>>>>>>> <skomatineni@nvidia.com>
>>>>>>>>>>>>>>>>> ---
>>>>>>>>>>>>>>> [snip]
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> +
>>>>>>>>>>>>>>>>> +static const struct clk_ops pmc_clk_gate_ops = {
>>>>>>>>>>>>>>>>> +    .is_enabled = pmc_clk_is_enabled,
>>>>>>>>>>>>>>>>> +    .enable = pmc_clk_enable,
>>>>>>>>>>>>>>>>> +    .disable = pmc_clk_disable,
>>>>>>>>>>>>>>>>> +};
>>>>>>>>>>>>>>>> What's the benefit of separating GATE from the MUX?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> I think it could be a single clock.
>>>>>>>>>>>>>>> According to TRM:
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 1. GATE and MUX are separate entities.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 2. GATE is the parent of MUX (see PMC's CLK_OUT paths
>>>>>>>>>>>>>>> diagram
>>>>>>>>>>>>>>> in TRM).
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> 3. PMC doesn't gate EXTPERIPH clock but could "force-enable"
>>>>>>>>>>>>>>> it,
>>>>>>>>>>>>>>> correct?
>>>>>>>>>>> Was following existing clk-tegra-pmc as I am not sure of
>>>>>>>>>>> reason for
>>>>>>>>>>> having these clocks registered as separate mux and gate clocks.
>>>>>>>>>>>
>>>>>>>>>>> Yes, PMC clocks can be registered as single clock and can use
>>>>>>>>>>> clk_ops
>>>>>>>>>>> for set/get parent and enable/disable.
>>>>>>>>>>>
>>>>>>>>>>> enable/disable of PMC clocks is for force-enable to force the
>>>>>>>>>>> clock to
>>>>>>>>>>> run regardless of ACCEPT_REQ or INVERT_REQ.
>>>>>>>>>>>
>>>>>>>>>>>>>> 4. clk_m_div2/4 are internal PMC OSC dividers and thus these
>>>>>>>>>>>>>> clocks
>>>>>>>>>>>>>> should belong to PMC.
>>>>>>>>>>>>> Also, it should be "osc" and not "clk_m".
>>>>>>>>>>>> I followed the same parents as it were in existing
>>>>>>>>>>>> clk-tegra-pmc
>>>>>>>>>>>> driver.
>>>>>>>>>>>>
>>>>>>>>>>>> Yeah they are wrong and they should be from osc and not clk_m.
>>>>>>>>>>>>
>>>>>>>>>>>> Will fix in next version.
>>>>>>>>>>>>
>>>>>>>> Reg clk_m_div2/3, they are dividers at OSC pad and not really
>>>>>>>> internal
>>>>>>>> to PMC block.
>>>>>>>>
>>>>>>>> current clock driver creates clk_m_div clocks which should
>>>>>>>> actually be
>>>>>>>> osc_div2/osc_div4 clocks with osc as parent.
>>>>>>>>
>>>>>>>> There are no clk_m_div2 and clk_m_div4 from clk_m
>>>>>>>>
>>>>>>>> Will fix this in next version.
>>>>>>>>
>>>>>>>>>> Could you please describe the full EXTPERIPH clock topology and
>>>>>>>>>> how the
>>>>>>>>>> pinmux configuration is related to it all?
>>>>>>>>>>
>>>>>>>>>> What is internal to the Tegra chip and what are the external
>>>>>>>>>> outputs?
>>>>>>>>>>
>>>>>>>>>> Is it possible to bypass PMC on T30+ for the EXTPERIPH clocks?
>>>>>>>>> PMC CLK1/2/3 possible sources are OSC_DIV1, OSC_DIV2, OSC_DIV4,
>>>>>>>>> EXTPERIPH from CAR.
>>>>>>>>>
>>>>>>>>> OSC_DIV1/2/4 are with internal dividers at the OSC Pads
>>>>>>>>>
>>>>>>>>> EXTPERIPH is from CAR and it has reset and enable controls
>>>>>>>>> along with
>>>>>>>>> clock source selections to choose one of the PLLA_OUT0, CLK_S,
>>>>>>>>> PLLP_OUT0, CLK_M, PLLE_OUT0
>>>>>>>>>
>>>>>>>>> So, PMC CLK1/2/4 possible parents are OSC_DIV1, OSC_DIV2,
>>>>>>>>> OSC_DIV4,
>>>>>>>>> EXTERN.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> CLK1/2/3 also has Pinmux to route EXTPERIPH output on to these
>>>>>>>>> pins.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> When EXTERN output clock is selected for these PMC clocks thru
>>>>>>>>> CLKx_SRC_SEL, output clock is from driver by EXTPERIPH from CAR
>>>>>>>>> via
>>>>>>>>> Pinmux logic or driven as per CLKx_SRC_SEL bypassing pinmux
>>>>>>>>> based on
>>>>>>>>> CLKx_ACCEPT_REQ bit.
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> PMC Clock control register has bit CLKx_ACCEPT_REQ
>>>>>>>>> When CLKx_ACCEPT_REQ = 0, output clock driver is from by EXTPERIPH
>>>>>>>>> through the pinmux
>>>>>>>>> When CLKx_ACCEPT_REQ = 1, output clock is based on CLKx_SRC_SEL
>>>>>>>>> bits
>>>>>>>>> (OSC_DIV1/2/4 and EXTPERIPH clock bypassing the pinmux)
>>>>>>>>>
>>>>>>>>> FORCE_EN bit in PMC CLock control register forces the clock to run
>>>>>>>>> regardless of this.
>>>>>>> PMC clock gate is based on the state of CLKx_ACCEPT_REQ and FORCE_EN
>>>>>>> like explained above.
>>>>>>>
>>>>>>> CLKx_ACCEPT_REQ is 0 default and FORCE_EN acts as gate to
>>>>>>> enable/disable
>>>>>>> EXTPERIPH clock output to PMC CLK_OUT_1/2/3.
>>>>>> [and to enable OSC as well]
>>>>>>
>>>>>>> So I believe we need to register as MUX and Gate rather than as a
>>>>>>> single
>>>>>>> clock. Please confirm.
>>>>>> 1. The force-enabling is applied to both OSC and EXTERN sources of
>>>>>> PMC_CLK_OUT_x by PMC at once.
>>>>>>
>>>>>> 2. Both of PMC's force-enabling and OSC/EXTERN selection is internal
>>>>>> to PMC.
>>>>>>
>>>>>> Should be better to define it as a single "pmc_clk_out_x". I don't
>>>>>> see
>>>>>> any good reasons for differentiating PMC's Gate from the MUX, it's a
>>>>>> single hardware unit from a point of view of the rest of the system.
>>>>>>
>>>>>> Peter, do you have any objections?
>>>>> We added fallback option for audio mclk and also added check for
>>>>> assigned-clock-parents dt property in audio driver and if its not then
>>>>> we do parent init configuration in audio driver.
>>>>>
>>>>> Current clock driver creates 2 separate clocks clk_out_1_mux and
>>>>> clk_out_1 for each pmc clock in clock driver and uses extern1 as
>>>>> parent to clk_out_1_mux and clk_out_1_mux is parent to clk_out_1.
>>>>>
>>>>> With change of registering each pmc clock as a single clock, when we
>>>>> do parent init assignment in audio driver when
>>>>> assigned-clock-properties are not used in DT (as we removed parent
>>>>> inits for extern and clk_outs from clock driver), we should still try
>>>>> to get clock based on clk_out_1_mux as parent assignment of extern1 is
>>>>> for clk_out_1_mux as per existing clock tree.
>>>>>
>>>>> clk_out_1_mux clock retrieve will fail with this change of single
>>>>> clock when any new platform device tree doesn't specify
>>>>> assigned-clock-parents properties and tegra_asoc_utils_init fails.
>>> You made the PMC/CaR changes before the audio changes, the clk_out_1_mux
>>> won't exist for the audio driver patches.
>>>
>>> If you care about bisect-ability of the patches, then the clock and
>>> audio changes need to be done in a single patch. But I don't think that
>>> it's worthwhile.
>>>
>>>>> With single clock, extern1 is the parent for clk_out_1 and with
>>>>> separate clocks for mux and gate, extern1 is the parent for
>>>>> clk_out_1_mux.
>>>> If we move to single clock now, it need one more additional fallback
>>>> implementation in audio driver during parent configuration as
>>>> clk_out_1_mux will not be there with single clock change and
>>>> old/current
>>>> kernel has it as it uses separate clocks for pmc mux and gate.
>>> Why additional fallback? Additional to what?
>>>
>>>> Also, with single clock for both PMC mux and gate now, new DT should
>>>> use
>>>> extern1 as parent to CLK_OUT_1 as CLK_OUT_1_MUX will not be there old
>>>> PMC dt-bindings has separate clocks for MUX (CLK_OUT_1_MUX) and gate
>>>> (CLK_OUT_1)
>>>>
>>>> DT bindings will not be compatible b/w old and new changes if we
>>>> move to
>>>> Single PMC clock now.
>>> Sorry, I don't understand what you're meaning by the "new changes".
>>>
>>>> Should we go with same separate clocks to have it compatible to avoid
>>>> all this?
>>>>
>> The reason we added mclk fallback and also for doing parent
>> configuration based on presence of assigned-clock-parents property is
>> to have old dt compatible with new kernel and also to have new dt
>> compatible with old kernel.
>>
>> So the point I was mentioning is to have new DT to work with old
>> kernel, setting extern1 as parent to clk_out_1 (with single pmc clock)
>> through assigned-clock-parents in DT will fail as old kernel has mux
>> and gate as separate clocks and parent configuration is for mux clock
>> (clk_out_1_mux)
>>
> Sorry never mind, with old kernel clock driver does all parent
> configuration so should be ok. So no additional fallbacks are needed
> except to the one we already added.
> 
> OK, So its just that changes are slightly more to switch to single clock
> compared to using separate clocks as gate clk_ops (which are needed
> anyway for blink control) of clock enable and disable can't be used for
> clk_out_1 enable/disable and need additional clk_enable and disable
> callbacks.
> 
> Will make changes to use single clock..

Please wait for the Peter's reply.