linux-kernel - Re: [PATCH 0/3] clk: meson: add support for PCIE PLL

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Message-ID: <2f8d217befcc4fdec36e5a31947cccfe74ccd49f.camel@baylibre.com>
Date:   Tue, 19 Mar 2019 11:01:34 +0100
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Neil Armstrong <narmstrong@...libre.com>
Cc:     linux-clk@...r.kernel.org, linux-amlogic@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] clk: meson: add support for PCIE PLL

On Thu, 2019-03-07 at 15:14 +0100, Neil Armstrong wrote:
> The Amlogic G12A SoCs embeds a dedicated PLL to feed the USB3+PCIE
> Combo PHY. This PLL needs a very specific and strict register sequence
> in order to correcly enable it and deliver the 100MHz reference clock
> to the Analog PHY.
> 
> After lot of trials and errors, and since this PLL will ever feed 100MHz
> with a static configuration, it is simpler to setup a dedicated ops
> structure with a custom _enable() op applying the init register sequence.
> 
> The rate calculation ops are kept in order to keep the nominal read
> ops as-in, but set_rate is removed.
> 
> With this setup, the PLL can be enabled and disable safely and always have
> the recommended PLL setup to feed the USB3+PCIE Combo PHY.
> 
> Neil Armstrong (3):
>   clk: meson-pll: add reduced specific clk_ops for G12A PCIe PLL
>   dt-bindings: clk: g12a-clkc: add PCIE PLL clock ID
>   clk: meson-g12a: add PCIE PLL clocks
> 
>  drivers/clk/meson/clk-pll.c           |  26 ++++++
>  drivers/clk/meson/clk-pll.h           |   1 +
>  drivers/clk/meson/g12a.c              | 118 ++++++++++++++++++++++++++
>  drivers/clk/meson/g12a.h              |   5 +-
>  include/dt-bindings/clock/g12a-clkc.h |   1 +
>  5 files changed, 150 insertions(+), 1 deletion(-)

Well this PLL is indeed a nasty one ;)

Acked-by: Jerome Brunet <jbrunet@...libre.com>