linux-kernel - Re: [PATCH] scsi: ufs: Consider device limitations for dma

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Date:   Mon, 14 Jan 2019 03:11:09 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Vinayak Holikatti <vinholikatti@...il.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH] scsi: ufs: Consider device limitations for dma_mask

On Fri, Jan 11, 2019 at 02:54:02PM -0800, Bjorn Andersson wrote:
>   */
>  static int ufshcd_set_dma_mask(struct ufs_hba *hba)
>  {
> -	if (hba->capabilities & MASK_64_ADDRESSING_SUPPORT) {
> -		if (!dma_set_mask_and_coherent(hba->dev, DMA_BIT_MASK(64)))
> -			return 0;
> -	}
> -	return dma_set_mask_and_coherent(hba->dev, DMA_BIT_MASK(32));
> +	u64 dma_mask = dma_get_mask(hba->dev);
> +
> +	if (hba->capabilities & MASK_64_ADDRESSING_SUPPORT)
> +		dma_mask &= DMA_BIT_MASK(64);
> +	else
> +		dma_mask &= DMA_BIT_MASK(32);
> +
> +	return dma_set_mask_and_coherent(hba->dev, dma_mask);

NAK.  ufshcd clearly is in charge of setting the dma mask, so reading
it back from someone else who might have set it is completely bogus.

You either need to introduce a quirk or a way to communicate the
different limit so that it can be set by the core.