Re: using DMA-API on ARM

From: Catalin Marinas
Date: Tue Dec 09 2014 - 06:54:42 EST

On Tue, Dec 09, 2014 at 10:29:05AM +0000, Russell King - ARM Linux wrote:
> On Tue, Dec 09, 2014 at 11:19:40AM +0100, Arend van Spriel wrote:
> > The issue did not trigger overnight so it seems setting bit 22 <Shared
> > Attribute _Override_ Enable> solves the issue over here. Now the question is
> > how to move forward with this. As I understood from Catalin this patch was
> > not included as it was not considered responsibility of the linux kernel.
> It is preferable for firmware to configure the L2 cache appropriately,
> which includes things like the prefetch offsets as well as feature bits
> like bit 22.
> I think what I'll do is queue up a patch which adds a warning if bit 22
> is not set, suggesting that firmware is updated to set this bit.

I'm fine with a (big) warning on this bit. But when you boot in secure
mode on 32-bit, do we still have a read/modify/write sequence for
L2X0_AUX_CTRL? A quick look at l2c310_enable() didn't reveal this (the
code has changed since I proposed the bit 22 setting patch).

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