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

Maxime Ripard
2017-07-25T07:32:33Z

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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 With the new mode, the 2 delay clocks are no longer active.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@csie.org>

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

Thanks!
Maxime

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

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