linux-kernel - Re: [PATCH 1/2] remoteproc: use a flag to detect the presence of IOMMU

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Date:	Tue, 29 Jul 2014 13:57:10 +0300
From:	Ohad Ben-Cohen <ohad@...ery.com>
To:	Suman Anna <s-anna@...com>
Cc:	Dave Gerlach <d-gerlach@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	Robert Tivy <rtivy@...com>
Subject: Re: [PATCH 1/2] remoteproc: use a flag to detect the presence of IOMMU

Hi Suman,

On Tue, Jul 8, 2014 at 7:22 PM, Suman Anna <s-anna@...com> wrote:
> The remoteproc driver core currently relies on iommu_present() on
> the bus the device is on, to perform MMU management. However, this
> logic doesn't scale for multi-arch, especially for processors that
> do not have an IOMMU.

Is there a specific hw/scenario where you need this? Can you please
provide more details about it?

Ideally we should add them to the commit log as well.

> The individual platform implementations are required to set this
> flag appropriately. The default setting is to not have an MMU.

Let's explicitly set the default please so this would be clear for
users reading the code.

> Cc: Sjur Brændeland <sjur.brandeland@...ricsson.com>

Sjur is no longer with STE, so no point in cc'ing his old email address.

> +       /*
> +        * All existing OMAP IPU and DSP processors do have an MMU, and
> +        * are expected to use MMU, so this statement suffices.
> +        * XXX: Replace this logic if and when a need arises.

The last XXX comment is always true for any kernel code, so I'd drop it.

Thanks,
Ohad.
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