linux-kernel - Re: [PATCH v2 6/6] arm64: allwinner: a64: Increase the MMC max frequency

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Date:   Wed, 11 Jan 2017 14:44:00 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Chen-Yu Tsai <wens@...e.org>, Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Andre Przywara <andre.przywara@....com>
Subject: Re: [PATCH v2 6/6] arm64: allwinner: a64: Increase the MMC max frequency

On Wed, Jan 11, 2017 at 3:15 AM, Maxime Ripard
<maxime.ripard@...e-electrons.com> wrote:
> Hi,
>
> On Tue, Jan 10, 2017 at 01:01:20AM +0800, Chen-Yu Tsai wrote:
>> On Tue, Jan 10, 2017 at 12:46 AM, Maxime Ripard
>> <maxime.ripard@...e-electrons.com> wrote:
>> > All the controllers can have a maximum frequency of 200MHz.
>> >
>> > Since older SoCs cannot go that high, we cannot change the default maximum
>> > frequency, but fortunately for us we have a property for that in the DT.
>> >
>> > This also has the side effect of allowing to use the MMC HS200 mode for the
>> > boards that support it (with either 1.2v or 1.8v IOs).
>> >
>> > Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
>> > ---
>> >  arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi | 3 +++
>> >  1 file changed, 3 insertions(+), 0 deletions(-)
>> >
>> > diff --git a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
>> > index 8e149498e096..f46ae965cf5b 100644
>> > --- a/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
>> > +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi
>> > @@ -332,6 +332,7 @@
>> >                         resets = <&ccu RST_BUS_MMC0>;
>> >                         reset-names = "ahb";
>> >                         interrupts = <GIC_SPI 60 IRQ_TYPE_LEVEL_HIGH>;
>> > +                       max-frequency = <200000000>;
>>
>> You also have to set one of MMC_CAP2_HS200* in the driver,
>> or mmc-hs200-1_8v or mmc-hs200-1_2v in the device tree to
>> actually use HS200, right?
>
> Yes, but that requires a board with 1.8V IOs to work properly, which
> not all board use, so it's probably best to enable it in the board
> DTS.

It's limited by the vqmmc regulator. Either way the host controller
supports it right?

ChenYu