linux-kernel - Re: [PATCH 2/2] AT91 slow-clock resume: don't restore the PLL settings when the PLL was off

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Date:	Tue, 13 Apr 2010 10:14:53 +0200
From:	Andrew Victor <avictor.za@...il.com>
To:	Anders Larsen <al@...rsen.net>
Cc:	Julien Langer <julien.langer@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	Russell King <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] AT91 slow-clock resume: don't restore the PLL 
	settings when the PLL was off

hi Anders,

> at91: slow-clock resume: Don't wait for a disabled PLL to lock.
>
> We run into this problem with the PLLB on the at91: ohci-at91 disables the PLLB
> when going to suspend. The slowclock code however tries to do the same: It
> saves the PLLB register value and when restoring the value during resume, it
> waits for the PLLB to lock again. However the PLL will never lock and the loop
> would run into its timeout because the slowclock code just stored and restored
> an empty register.
> This fixes the problem by only restoring PLLA/PLLB when they were enabled
> at suspend time.
>
> Signed-off-by: Anders Larsen <al@...rsen.net>
> Cc: Andrew Victor <avictor.za@...il.com>
> Cc: Julien Langer <julien.langer@...il.com>

> +       tst     r3, #(AT91_PMC_MUL &  0xff0000)
> +       bne     1f
> +       tst     r3, #(AT91_PMC_MUL & ~0xff0000)
> +       beq     2f
> +1:
>        wait_pllblock
> +2:

AT91_PMC_MUL is 11 bits (so 0x7ff0000)

Is the mask (0xff0000) correct in the above code?
It looks like wait_pllblock will be skipped if the MUL field is set to
0x100, 0x200, 0x300, etc.


Regards,
  Andrew Victor
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