Re: [PATCH] clk: samsung: exynos5433: use clock_ignore_unused flag for SPI3 related clocks

From: Andi Shyti
Date: Mon Jun 20 2016 - 01:42:23 EST


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