[PATCH 0/8] i.MX early debug UART clock fixes

[Lucas Stach]

Am Donnerstag, den 27.08.2015, 18:39 +0200 schrieb Lucas Stach:
> This series fixes a long standing interaction issue between the
> kernels early debug facilities and the i.MX clock drivers.
> 
> Both earlyprintk and earlycon rely on the bootloader setup clocks
> for the UARTs to be retained during kernel init. As those clocks are
> only enabled in hardware, but not referenced in software they (or even
> their parent clocks) may get disabled as a result of other clocks being
> en-/disabled during boot.
> 
> This results in missing messages from the early debug console until the
> regular system console takes over, or even worse system hangs in response
> to unclocked register accesses. This renders those debugging facilities a
> lot less useful.
> 
> The fix implemented here is to check if any of this early debugging is
> enabled and keep the UART clocks referenced and enabled in that case.
> The clocks will then only be disabled at the end of kernel init, at which
> point the real console should have taken over and the early outputs being
> disabled.
> 
> I've runtime tested this on i.MX6Q and i.MX53, other platforms are only
> compile tested. This is mostly a mechanical change, but still I would
> appreciate some testing.
> 
And Philipp noted that passing in a list of clocks from the clock
providers look a lot better than the current direct clock enable calling
and the needed callback.

I'm self-nacking this series, so I can spin a V2 with changes as above.

> Regards,
> Lucas
> 
> Lucas Stach (8):
>   clk: imx: add common logic to detect early UART usage
>   clk: imx25: retain early UART clocks during kernel init
>   clk: imx27: retain early UART clocks during kernel init
>   clk: imx31: retain early UART clocks during kernel init
>   clk: imx35: retain early UART clocks during kernel init
>   clk: imx5: retain early UART clocks during kernel init
>   clk: imx6: retain early UART clocks during kernel init
>   clk: imx7d: retain early UART clocks during kernel init
> 
>  drivers/clk/imx/clk-imx25.c       | 20 ++++++++++++++++++++
>  drivers/clk/imx/clk-imx27.c       | 22 ++++++++++++++++++++++
>  drivers/clk/imx/clk-imx31.c       | 20 ++++++++++++++++++++
>  drivers/clk/imx/clk-imx35.c       | 16 ++++++++++++++++
>  drivers/clk/imx/clk-imx51-imx53.c | 28 ++++++++++++++++++++++++++++
>  drivers/clk/imx/clk-imx6q.c       | 12 ++++++++++++
>  drivers/clk/imx/clk-imx6sl.c      | 12 ++++++++++++
>  drivers/clk/imx/clk-imx6sx.c      | 12 ++++++++++++
>  drivers/clk/imx/clk-imx7d.c       | 22 ++++++++++++++++++++++
>  drivers/clk/imx/clk.c             | 33 +++++++++++++++++++++++++++++++++
>  drivers/clk/imx/clk.h             |  2 ++
>  11 files changed, 199 insertions(+)
> 

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