linux-kernel - Re: [PATCH 1/3] crypto: ccp - Add function to allocate and free memory using DMA APIs

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Message-ID: <be7a774e-54d7-4ebf-8476-de137c47f020@amd.com>
Date:   Mon, 30 Oct 2023 11:35:57 +0530
From:   "NK, JESHWANTHKUMAR" <jeshwanthkumar.nk@....com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     thomas.lendacky@....com, john.allen@....com,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        jens.wiklander@...aro.org, sumit.garg@...aro.org,
        jarkko.nikula@...ux.intel.com, mario.limonciello@....com,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        op-tee@...ts.trustedfirmware.org,
        Mythri.Pandeshwarakrishna@....com, Devaraj.Rangasamy@....com,
        Rijo-john.Thomas@....com, nimesh.easow@....com
Subject: Re: [PATCH 1/3] crypto: ccp - Add function to allocate and free
 memory using DMA APIs

Hi Christoph,

On 27-Oct-23 10:54 AM, Christoph Hellwig wrote:
> On Wed, Oct 25, 2023 at 12:26:58PM +0530, jeshwank wrote:
>> +	tee_buf->vaddr = dma_alloc_coherent(psp->dev, size, &tee_buf->dma, gfp);
>> +	if (!tee_buf->vaddr || !tee_buf->dma) {
>> +		kfree(tee_buf);
>> +		return NULL;
>> +	}
>> +
>> +	tee_buf->size = size;
>> +
>> +	/* Check whether IOMMU is present. If present, translate IOVA
>> +	 * to physical address, else the dma handle is the physical
>> +	 * address.
>> +	 */
>> +	dom = iommu_get_domain_for_dev(psp->dev);
>> +	if (dom)
>> +		tee_buf->paddr = iommu_iova_to_phys(dom, tee_buf->dma);
>> +	else
> No, you can't mix the DMA API and iommu API.  You need to stick to one
> or the other.
Can you please elaborate?