Re: [PATCH v2] iommu/rockchip: Add missing set_platform_dma_ops callback

From: Jason Gunthorpe <jgg@ziepe.ca>
To: John Keeping <john@metanate.com>
Cc: Steven Price <steven.price@arm.com>,
	Heiko Stuebner <heiko@sntech.de>, Joerg Roedel <joro@8bytes.org>,
	Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org
Subject: Re: [PATCH v2] iommu/rockchip: Add missing set_platform_dma_ops callback
Date: Mon, 27 Mar 2023 12:26:55 -0300	[thread overview]
Message-ID: <ZCG1v9hRybc/951e@ziepe.ca> (raw)
In-Reply-To: <ZCGpmHUWyZVaeIIx@donbot>

On Mon, Mar 27, 2023 at 03:35:04PM +0100, John Keeping wrote:
> On Fri, Mar 24, 2023 at 11:11:27AM +0000, Steven Price wrote:
> > Similar to exynos, we need a set_platform_dma_ops() callback for proper
> > operation on ARM 32 bit after recent changes in the IOMMU framework
> > (detach ops removal). But also the use of a NULL domain is confusing.
> > 
> > Rework the code to have a singleton rk_identity_domain which is assigned
> > to domain when using an identity mapping rather than "detaching". This
> > makes the code easier to reason about.
> > 
> > Signed-off-by: Steven Price <steven.price@arm.com>
> > ---
> > Changes since v1[1]:
> > 
> >  * Reworked the code to avoid a NULL domain, instead a singleton
> >    rk_identity_domain is used instead. The 'detach' language is no
> >    longer used.
> > 
> > [1] https://lore.kernel.org/r/20230315164152.333251-1-steven.price%40arm.com
> > 
> >  drivers/iommu/rockchip-iommu.c | 50 ++++++++++++++++++++++++++--------
> >  1 file changed, 39 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
> > index f30db22ea5d7..437541004994 100644
> > --- a/drivers/iommu/rockchip-iommu.c
> > +++ b/drivers/iommu/rockchip-iommu.c
> [snip]
> > +static struct iommu_domain rk_identity_domain = {
> > +	.type = IOMMU_DOMAIN_IDENTITY,
> > +	.ops = &rk_identity_ops,
> > +};
> > +
> > +#ifdef CONFIG_ARM
> 
> Is this #ifdef needed?  I can't see anything ARM-specific about this
> function or .set_platform_dma_ops.

set_platform_dma_ops is never called on ARM64.

> Not shown in the patch are the pm_runtime hooks.  Do they need to
> change like this?

Most likely yes

Jason