linux-kernel - Re: [PATCH v3 01/10] clk: sunxi-ng: Add interface to query or configure MMC timing modes.

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Message-ID: <20170725073229.fbm7ead455oudftc@flea>
Date:   Tue, 25 Jul 2017 09:32:29 +0200
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-mmc@...r.kernel.org,
        linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com
Subject: Re: [PATCH v3 01/10] clk: sunxi-ng: Add interface to query or
 configure MMC timing modes.

On Mon, Jul 24, 2017 at 09:58:56PM +0800, Chen-Yu Tsai wrote:
> Starting with the A83T SoC, Allwinner introduced a new timing mode for
> its MMC clocks. The new mode changes how the MMC controller sample and
> output clocks are delayed to match chip and board specifics. There are
> two controls for this, one on the CCU side controlling how the clocks
> behave, and one in the MMC controller controlling what inputs to take
> and how to route them.
> 
> In the old mode, the MMC clock had 2 child clocks providing the output
> and sample clocks, which could be delayed by a number of clock cycles
> measured from the MMC clock's parent.
> 
> With the new mode, the 2 delay clocks are no longer active. Instead,
> the delays and associated controls are moved into the MMC controller.
> The output of the MMC clock is also halved.
> 
> The difference in how things are wired between the modes means that the
> clock controls and the MMC controls must match. To achieve this in a
> clear, explicit way, we introduce two functions for the MMC driver to
> use: one queries the hardware for the current mode set, and the other
> allows the MMC driver to request a mode.
> 
> Signed-off-by: Chen-Yu Tsai <wens@...e.org>

Acked-by: Maxime Ripard <maxime.ripard@...e-electrons.com>

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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