linux-kernel - Re: [PATCH 06/13] drm/etnaviv: Use sychronized interface of the IOMMU-API

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Message-ID: <1502978634.19806.27.camel@pengutronix.de>
Date:   Thu, 17 Aug 2017 16:03:54 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Joerg Roedel <jroedel@...e.de>
Cc:     Joerg Roedel <joro@...tes.org>, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org,
        Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
        Russell King <linux+etnaviv@...linux.org.uk>,
        Christian Gmeiner <christian.gmeiner@...il.com>,
        David Airlie <airlied@...ux.ie>, etnaviv@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH 06/13] drm/etnaviv: Use sychronized interface of the
 IOMMU-API

Am Donnerstag, den 17.08.2017, 15:45 +0200 schrieb Joerg Roedel:
> Hi Lucas,
> 
> On Thu, Aug 17, 2017 at 03:32:38PM +0200, Lucas Stach wrote:
> > I don't think this is necessary. Etnaviv has managed and batched up TLB
> > flushes from day 1, as they don't happen through the MMU MMIO interface,
> > but through the GPU command stream.
> > 
> > So if my understanding of this series is correct, Etnaviv is just fine
> > with the changed semantics of the unsynchronized map/unmap calls.
> 
> This is not about any TLB on the GPU that could be flushed through the
> GPU command stream, but about the TLB in the IOMMU device. Or is this
> actually the same on this hardware? Which IOMMU-driver is use there?

There is no IOMMU driver in use. Etnaviv just uses part of the IOMMU API
to manage the GPU internal MMU, see
drivers/gpu/drm/etnaviv/etnaviv_iommu.c

Regards,
Lucas