linux-kernel - Re: [PATCH 2/2] iommu/tegra: gart: Reserve iomem resource

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Date:	Mon, 21 May 2012 16:11:52 +0200
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	Hiroshi DOYU <hdoyu@...dia.com>
Cc:	linux-tegra@...r.kernel.org, Joerg Roedel <joerg.roedel@....com>,
	Stephen Warren <swarren@...dotorg.org>,
	Bharat Nihalani <bnihalani@...dia.com>,
	Vandana Salve <vsalve@...dia.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] iommu/tegra: gart: Reserve iomem resource

* Hiroshi DOYU wrote:
> GART Register/Aperture range should be reserved.
> 
> Signed-off-by: Hiroshi DOYU <hdoyu@...dia.com>
> ---
>  drivers/iommu/tegra-gart.c |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/iommu/tegra-gart.c b/drivers/iommu/tegra-gart.c
> index 33a23b6..a431006 100644
> --- a/drivers/iommu/tegra-gart.c
> +++ b/drivers/iommu/tegra-gart.c
> @@ -366,12 +366,18 @@ static int tegra_gart_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  	}
>  
> -	gart_regs = devm_ioremap(dev, res->start, resource_size(res));
> +	gart_regs = devm_request_and_ioremap(dev, res);
>  	if (!gart_regs) {
>  		dev_err(dev, "failed to remap GART registers\n");
>  		return -ENXIO;
>  	}
>  
> +	if (!devm_request_mem_region(dev, res_remap->start,
> +				     resource_size(res_remap), dev_name(dev))) {
> +		dev_err(dev, "failed to reserve GART aperture\n");
> +		return -EBUSY;
> +	}
> +

I'm not so sure that this is a good idea. If the GART driver requests the
GART aperture, then users of the GART aperture (e.g. the DRM driver) will no
longer be able to use it.

Thierry

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