linux-kernel - Re: [PATCH v2 2/2] iommu: apple-dart: Allow mismatched bypass support

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Message-ID: <Z8HnWdgPNMmCoXtX@blossom>
Date: Fri, 28 Feb 2025 11:42:01 -0500
From: Alyssa Rosenzweig <alyssa@...enzweig.io>
To: fnkl.kernel@...il.com
Cc: Sven Peter <sven@...npeter.dev>, Janne Grunau <j@...nau.net>,
	Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>, asahi@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org, Hector Martin <marcan@...can.st>
Subject: Re: [PATCH v2 2/2] iommu: apple-dart: Allow mismatched bypass support

Reviewed-by: Alyssa Rosenzweig <alyssa@...enzweig.io>

Le Fri , Feb 28, 2025 at 05:32:08PM +0100, Sasha Finkelstein via B4 Relay a écrit :
> From: Hector Martin <marcan@...can.st>
> 
> This is needed by ISP, which has DART0 with bypass and DART1/2 without.
> 
> Signed-off-by: Hector Martin <marcan@...can.st>
> Signed-off-by: Sasha Finkelstein <fnkl.kernel@...il.com>
> ---
>  drivers/iommu/apple-dart.c | 17 ++++++++++++-----
>  1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
> index edb2fb22333506d7c64ad1b6321df00ebfd07747..13ccb801f52a4d34f6653f78e92787af7dfed1bc 100644
> --- a/drivers/iommu/apple-dart.c
> +++ b/drivers/iommu/apple-dart.c
> @@ -277,6 +277,9 @@ struct apple_dart_domain {
>   * @streams: streams for this device
>   */
>  struct apple_dart_master_cfg {
> +	/* Intersection of DART capabilitles */
> +	u32 supports_bypass : 1;
> +
>  	struct apple_dart_stream_map stream_maps[MAX_DARTS_PER_DEVICE];
>  };
>  
> @@ -684,7 +687,7 @@ static int apple_dart_attach_dev_identity(struct iommu_domain *domain,
>  	struct apple_dart_stream_map *stream_map;
>  	int i;
>  
> -	if (!cfg->stream_maps[0].dart->supports_bypass)
> +	if (!cfg->supports_bypass)
>  		return -EINVAL;
>  
>  	for_each_stream_map(i, cfg, stream_map)
> @@ -792,20 +795,24 @@ static int apple_dart_of_xlate(struct device *dev,
>  		return -EINVAL;
>  	sid = args->args[0];
>  
> -	if (!cfg)
> +	if (!cfg) {
>  		cfg = kzalloc(sizeof(*cfg), GFP_KERNEL);
> +
> +		/* Will be ANDed with DART capabilities */
> +		cfg->supports_bypass = true;
> +	}
>  	if (!cfg)
>  		return -ENOMEM;
>  	dev_iommu_priv_set(dev, cfg);
>  
>  	cfg_dart = cfg->stream_maps[0].dart;
>  	if (cfg_dart) {
> -		if (cfg_dart->supports_bypass != dart->supports_bypass)
> -			return -EINVAL;
>  		if (cfg_dart->pgsize != dart->pgsize)
>  			return -EINVAL;
>  	}
>  
> +	cfg->supports_bypass &= dart->supports_bypass;
> +
>  	for (i = 0; i < MAX_DARTS_PER_DEVICE; ++i) {
>  		if (cfg->stream_maps[i].dart == dart) {
>  			set_bit(sid, cfg->stream_maps[i].sidmap);
> @@ -945,7 +952,7 @@ static int apple_dart_def_domain_type(struct device *dev)
>  
>  	if (cfg->stream_maps[0].dart->pgsize > PAGE_SIZE)
>  		return IOMMU_DOMAIN_IDENTITY;
> -	if (!cfg->stream_maps[0].dart->supports_bypass)
> +	if (!cfg->supports_bypass)
>  		return IOMMU_DOMAIN_DMA;
>  
>  	return 0;
> 
> -- 
> 2.48.1
> 
>