linux-kernel - Re: [PATCH 2/2] scsi: Align queue to ARCH_DMA

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Date:   Mon, 11 Sep 2017 00:39:06 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Huacai Chen <chenhc@...ote.com>
Cc:     "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Fuxin Zhang <zhangfx@...ote.com>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 2/2] scsi: Align queue to ARCH_DMA_MINALIGN in
 non-coherent DMA mode

> +	if (plat_device_is_coherent(dev))

We can't just call platform device code.  We'll need a proper
DMA API call for this.

> +		blk_queue_dma_alignment(q, 0x04 - 1);
> +	else
> +		blk_queue_dma_alignment(q, dma_get_cache_alignment() - 1);

Which we already have with dma_get_cache_alignment, except that it
doesn't take a struct device pointer and doesn't call into dma_map
ops.  So please add a struct device argument to dma_get_cache_alignment,
and let it call into dma_map_ops where needed.

With that you can replace the above with:

	blk_queue_dma_alignment(q,
			max(0x04U, dma_get_cache_alignment(dev)) - 1);