linux-kernel - Re: [PATCH] irqchip/gic-v3: Allow 'dma-noncoherent' property for ITS

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Message-ID: <87mt5jksua.wl-maz@kernel.org>
Date:   Sun, 12 Feb 2023 11:48:13 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Ben Dai <ben.dai9703@...il.com>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irqchip/gic-v3: Allow 'dma-noncoherent' property for ITS

On Sun, 12 Feb 2023 09:35:05 +0000,
Ben Dai <ben.dai9703@...il.com> wrote:
> 
> Currently the ITS driver expects the hardware to report whether it is
> shareable, but according to the description of the GITS_CBASER register
> in the GICv3 architecture specification:
>  > It is IMPLEMENTATION DEFINED whether this field has a fixed value or
>  > can be programmed by software. Implementing this field with a fixed
>  > value is deprecated.
> 
> It means that the hardware may expect the software to correctly configure
> the access attributes of the ITS. In order to support those designs where
> ITS and CPU are not in a coherent domain, allow 'dma-noncoherent' property
> for ITS.

No. This is an integration bug, most likely a Rockchip quality
design. I have repeatedly explained how to deal with this, and I'm not
going to do that again. Please search the list archives.

I will not be taking this sort of patch.

	M.

-- 
Without deviation from the norm, progress is not possible.