Re: [PATCH] [RFC] ARM: shmobile: koelsch-reference: Work around core clock issues

[Ben Dooks <ben.dooks@codethink.co.uk>]

On 14/03/14 12:39, Geert Uytterhoeven wrote:
> Hi Ben, Laurent,
>
> On Fri, Mar 14, 2014 at 12:10 PM, Ben Dooks <ben.dooks@codethink.co.uk> wrote:
>> On 14/03/14 11:02, Laurent Pinchart wrote:
>>> On Thursday 13 March 2014 15:29:30 Geert Uytterhoeven wrote:
>>>> From: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
>>>>
>>>> Due to issues with runtime PM clock management, clocks not explicitly
>>>> managed by their drivers may not be enabled at all, or be inadvertently
>>>> disabled by the clk_disable_unused() late initcall.
>>>>
>>>> Until this is fixed, add a temporary workaround, calling
>>>> shmobile_clk_workaround() with enable = true.
>>>>
>>>> For now this enables the clocks for: ether, i2c2, msiof0, qspi_mod, and
>>>> thermal. More clocks can be added if needed.
>>>
>>> This should do the job, but as you mentioned, it's a crude hack. As we're
>>> targeting v3.16, is there a chance we could fix the problem properly
>>> instead ?
>
> Of course the goal is to fix it for real, so the crude hack will no longer
> be needed. But for now, it looks like a good short-term workaround.
>
>> The best fix would be to re-enable the PM and find out what is
>
> Sure, but in a multiplatform-aware way.
>
>> actually causing the external abort. However currently there is
>> no information in the manuals about anything we could find out from
>> the AXI busses as to what the source actually is.
>
> I re-applied your patch "ARM: shmobile: compile drivers/sh for
> CONFIG_ARCH_SHMOBILE_MULTI", and surprisingly, I no longer get
> the external abort.
>
> Some experimenting revealed it's due to the "ether" clock in the
> clk_enables[] array. As long as that's enabled early, the system seems

I did post an updated to ensure the MDIO bus is accessed with clock
enabled, but that has not cured the issue for me. I wonder if some
other part of the driver is also accessing the hardware without
the correct pm accesses.

-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius