linux-kernel - Re: [PATCH v2 8/8] irqchip, gicv3-its, cma: Use CMA for allocation of large device tables

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Date:   Thu, 16 Mar 2017 14:31:54 +0100
From:   Robert Richter <robert.richter@...ium.com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Shanker Donthineni <shankerd@...eaurora.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 8/8] irqchip, gicv3-its, cma: Use CMA for allocation
 of large device tables

On 15.03.17 18:46:22, Marc Zyngier wrote:
> On 15/03/17 18:37, Robert Richter wrote:
> > On 14.03.17 12:40:45, Shanker Donthineni wrote:

> >>> @@ -1698,6 +1706,9 @@ static int __init its_init_one(struct its_node *its)
> >>>  		return err;
> >>>  	}
> >>>  
> >>> +	/* Setup dma_ops for dmam_alloc_coherent() */
> >>> +	arch_setup_dma_ops(&its->dev, 0, 0, NULL, true);
> >>> +
> > 
> >> Why you are hard-coding DMA coherent property to true here ? It
> >> breaks the MSI(x) functionally on systems where ITS hardware doesn't
> >> support coherency.
> > 
> > Aren't current ITS tables coherent only?
> 
> No, there is no such guarantee. Actually, there is strictly no need for
> coherency, as the ITS tables are only written by the ITS itself, for its
> own purpose.

So no need to change that, right?

Thanks,

-Robert