linux-kernel - Re: [PATCH] iommu/of: Only do IOMMU lookup for available ones

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Message-ID: <767a9f59-be14-2103-6675-a2028742e663@arm.com>
Date:   Mon, 8 Jan 2018 11:45:03 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Jeffy Chen <jeffy.chen@...k-chips.com>,
        linux-kernel@...r.kernel.org
Cc:     jcliang@...omium.org, iommu@...ts.linux-foundation.org
Subject: Re: [PATCH] iommu/of: Only do IOMMU lookup for available ones

Hi Jeffy,

On 03/01/18 06:09, Jeffy Chen wrote:
> The for_each_matching_node_and_match() would return every matching
> nodes including unavailable ones.
> 
> It's pointless to init unavailable IOMMUs, so add a sanity check to
> avoid that.

Even better would be to clean up the last remaining init_fn user and get 
rid of the whole business. With the probe-deferral mechanism, early 
initialisation hooks are no longer needed, and the IOMMU_OF_DECLARE 
section really only remains as a way of detecting builtin drivers long 
before their registration initcalls run.

Robin.

> Signed-off-by: Jeffy Chen <jeffy.chen@...k-chips.com>
> ---
> 
>   drivers/iommu/of_iommu.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> index 50947ebb6d17..6f7456caa30d 100644
> --- a/drivers/iommu/of_iommu.c
> +++ b/drivers/iommu/of_iommu.c
> @@ -240,6 +240,9 @@ static int __init of_iommu_init(void)
>   	for_each_matching_node_and_match(np, matches, &match) {
>   		const of_iommu_init_fn init_fn = match->data;
>   
> +		if (!of_device_is_available(np))
> +			continue;
> +
>   		if (init_fn && init_fn(np))
>   			pr_err("Failed to initialise IOMMU %pOF\n", np);
>   	}
>