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Date: Mon, 20 Jun 2016 14:41:57 +0900
From: Andi Shyti <andi.shyti@samsung.com>
To: Tomasz Figa <tomasz.figa@gmail.com>
Cc: Andi Shyti <andi@etezian.org>, Chanwoo Choi <cw00.choi@samsung.com>,
        Sylwester Nawrocki <s.nawrocki@samsung.com>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@codeaurora.org>, Kukjin Kim <kgene@kernel.org>,
        Krzysztof Kozlowski <k.kozlowski@samsung.com>,
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        linux-kernel <linux-kernel@vger.kernel.org>,
        Jaehoon Chung <jh80.chung@samsung.com>,
        Andi Shyti <andi.shyti@samsung.com>
Subject: Re: [PATCH] clk: samsung: exynos5433: use clock_ignore_unused flag for
 SPI3 related clocks
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Hi Tomasz,

> >> > The SPI 3 bus uses two clocks, a bus clock and an input clock.
> >> > Do not disable the clocks when unused in order to allow access to
> >> > the SPI 3 device.
> >>
> >> If unused, why would access to SPI 3 device needed?
> >
> > because next I will submit a small driver which uses the SPI3.
> > Actually in the exynos5433 boards all the SPI are used but not all
> > the drivers are ported to mainline.
> 
> Then shouldn't the driver request the clocks and enable them? Or I'm
> missing something obvious? :)

the reason is that...

[ from the patch ]

>         GATE(CLK_SCLK_IOCLK_SPI3, "sclk_ioclk_spi3", "ioclk_spi3_clk_in",
> -                       ENABLE_SCLK_PERIC, 20, CLK_SET_RATE_PARENT, 0),
> +                       ENABLE_SCLK_PERIC, 20,
> +                       CLK_IGNORE_UNUSED | CLK_SET_RATE_PARENT, 0),

... the sclk_ioclk_spi3 is new in exynos5433 and there is no
implementation for enabling/disabling that particular clock...

>         GATE(CLK_SCLK_SPI3, "sclk_spi3", "sclk_spi3_peric", ENABLE_SCLK_PERIC,
> -                       18, CLK_SET_RATE_PARENT, 0),
> +                       18, CLK_IGNORE_UNUSED | CLK_SET_RATE_PARENT, 0),

... while in this case your question makes sense, but it depends
on which clock the device (s3c64xx) is requesting (from the DTS).
In any case, I kept it consistent with the SPI1, which falls in
the same case, as in mainline we don't have any DTS for
exynos5433 (yet!).

Thanks,
Andi