linux-kernel - Re: [PATCH 0/6] add the DDR clock controller on Meson8 and Meson8b

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Date:   Tue, 01 Oct 2019 15:33:04 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        linux-amlogic@...ts.infradead.org, devicetree@...r.kernel.org,
        khilman@...libre.com, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH 0/6] add the DDR clock controller on Meson8 and Meson8b


On Mon 23 Sep 2019 at 22:49, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:

> Hi Jerome,
>
> On Mon, Sep 23, 2019 at 12:06 PM Jerome Brunet <jbrunet@...libre.com> wrote:
>>
>> On Sat 21 Sep 2019 at 17:18, Martin Blumenstingl <martin.blumenstingl@...glemail.com> wrote:
>>
>> > Meson8 and Meson8b SoCs embed a DDR clock controller in their MMCBUS
>> > registers. This series:
>> > - adds support for this DDR clock controller (patches 0 and 1)
>> > - wires up the DDR PLL as input for two audio clocks (patches 2 and 3)
>>
>> Have you been able to validate somehow that DDR rate calculated by CCF
>> is the actual rate that gets to the audio clocks ?
> no, I haven't been able to validate this (yet)
>
>> While I understand the interest for completeness, I suspect the having
>> the DDR clock as an audio parent was just for debugging purpose. IOW,
>> I'm not sure if adding this parent is useful to an actual audio use
>> case. As far as audio would be concerned, I think we are better of
>> without this parent.
> there at least three other (potential) consumers of the ddr_pll clocks
> on the 32-bit SoCs:
> - CPU clock mux [0]
> - clk81 mux [1]
> - USB PHY [2]
>
> I have not validated any of these either
>

Then I would suggest to leave patch 4 out until we can somehow validate
this. 

>
>
> Martin
>
>
> [0] https://github.com/endlessm/u-boot-meson/blob/345ee7eb02903f5ecb1173ffb2cd36666e44ebed/board/amlogic/m8b_m201_v1/firmware/timming.c#L441
> [1] https://github.com/endlessm/u-boot-meson/blob/345ee7eb02903f5ecb1173ffb2cd36666e44ebed/board/amlogic/m8b_m201_v1/firmware/timming.c#L452
> [2] https://github.com/endlessm/u-boot-meson/blob/f1ee03e3f7547d03e1478cc1fc967a9e5a121d92/arch/arm/cpu/aml_meson/m8/firmware/usb_boot/platform.c#L22