Re: [PATCH v4 5/6] serial: 8250_dw: Add support for deferred probing

[Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

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On Wed, Jul 09, 2014 at 03:54:38PM +0800, Chen-Yu Tsai wrote:
> The 8250_dw driver fails to probe if the specified clock isn't
> registered at probe time. Even if a clock frequency is given,
> the required clock might be gated because it wasn't properly
> enabled.
> 
> This happened to me when the device is registered through DT,
> and the clock was part of an MFD, the PRCM found on A31 and A23
> SoCs. Unlike core clocks that are registered with OF_CLK_DECLARE,
> which happen almost immediately after the kernel starts, the
> clocks are registered as sub-devices of the PRCM MFD platform
> device. Even though devices are registered in the order they are
> found in the DT, the drivers are registered in a different,
> arbitrary order. It is possible that the 8250_dw driver is
> registered, and thus associated with the device and probed, before
> the clock driver is registered and probed.
> 
> 8250_dw then reports unable to get the clock, and fails. Without
> a working console, the kernel panics.
> 
> This patch adds support for deferred probe handling for the clock
> and reset controller.
> 
> Signed-off-by: Chen-Yu Tsai <wens-jdAy2FN1RRM@public.gmane.org>

Acked-by: Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>

Thanks!
Maxime

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

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