netdev - Re: [PATCH v2 3/3] dpaa2_eth: use new unmap and sync dma api variants

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Date:   Mon, 28 Oct 2019 10:55:05 +0000
From:   Laurentiu Tudor <laurentiu.tudor@....com>
To:     Jonathan Lemon <jlemon@...gsvamp.com>
CC:     "hch@....de" <hch@....de>, "joro@...tes.org" <joro@...tes.org>,
        Ioana Ciocoi Radulescu <ruxandra.radulescu@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Leo Li <leoyang.li@....com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        Diana Madalina Craciun <diana.craciun@....com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Madalin Bucur <madalin.bucur@....com>
Subject: Re: [PATCH v2 3/3] dpaa2_eth: use new unmap and sync dma api variants

Hi Jonathan,

On 25.10.2019 19:12, Jonathan Lemon wrote:
> 
> 
> On 24 Oct 2019, at 5:41, Laurentiu Tudor wrote:
> 
>> From: Laurentiu Tudor <laurentiu.tudor@....com>
>>
>> Convert this driver to usage of the newly introduced dma unmap and
>> sync DMA APIs. This will get rid of the unsupported direct usage of
>> iommu_iova_to_phys() API.
>>
>> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@....com>
>> ---
>>  .../net/ethernet/freescale/dpaa2/dpaa2-eth.c  | 40 +++++++------------
>>  .../net/ethernet/freescale/dpaa2/dpaa2-eth.h  |  1 -
>>  2 files changed, 15 insertions(+), 26 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c 
>> b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
>> index 19379bae0144..8c3391e6e598 100644
>> --- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
>> +++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
>> @@ -29,16 +29,6 @@ MODULE_LICENSE("Dual BSD/GPL");
>>  MODULE_AUTHOR("Freescale Semiconductor, Inc");
>>  MODULE_DESCRIPTION("Freescale DPAA2 Ethernet Driver");
>>
>> -static void *dpaa2_iova_to_virt(struct iommu_domain *domain,
>> -                dma_addr_t iova_addr)
>> -{
>> -    phys_addr_t phys_addr;
>> -
>> -    phys_addr = domain ? iommu_iova_to_phys(domain, iova_addr) : 
>> iova_addr;
>> -
>> -    return phys_to_virt(phys_addr);
>> -}
>> -
>>  static void validate_rx_csum(struct dpaa2_eth_priv *priv,
>>                   u32 fd_status,
>>                   struct sk_buff *skb)
>> @@ -85,9 +75,10 @@ static void free_rx_fd(struct dpaa2_eth_priv *priv,
>>      sgt = vaddr + dpaa2_fd_get_offset(fd);
>>      for (i = 1; i < DPAA2_ETH_MAX_SG_ENTRIES; i++) {
>>          addr = dpaa2_sg_get_addr(&sgt[i]);
>> -        sg_vaddr = dpaa2_iova_to_virt(priv->iommu_domain, addr);
>> -        dma_unmap_page(dev, addr, DPAA2_ETH_RX_BUF_SIZE,
>> -                   DMA_BIDIRECTIONAL);
>> +        sg_vaddr = page_to_virt
>> +                (dma_unmap_page_desc(dev, addr,
>> +                            DPAA2_ETH_RX_BUF_SIZE,
>> +                            DMA_BIDIRECTIONAL));
> 
> This is doing virt -> page -> virt.  Why not just have the new
> function return the VA corresponding to the addr, which would
> match the other functions?

I'd really like that as it would get rid of the page_to_virt() calls but 
it will break the symmetry with the dma_map_page() API. I'll let the 
maintainers decide.

---
Best Regards, Laurentiu