Re: [PATCH v2] scsi: ibmvscsi: Use dma_alloc_noncoherent() instead of get_zeroed_page/dma_map_single()

Tyrel Datwyler
2021-10-14T22:08:27Z

On 10/11/21 8:23 PM, Cai Huoqing wrote:
> Replacing get_zeroed_page/free_page/dma_map_single/dma_unmap_single()
> with dma_alloc_noncoherent/dma_free_noncoherent() helps to reduce
> code size, and simplify the code, and the hardware can keeep DMA
> coherent itsel
Not sure why the switch from coherent in v1 to noncoherent in v2. I think that
was unnecessary and I believe requires explicit synchronization via
dma_sync_single_{for_device|for_cpu} calls.

Further, as both kernel-bot and Nathan have already pointed out this doesn't
even compile.

-Tyrel

>
> Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
> ---
> v1->v2:
> *Change to dma_alloc/free_noncoherent from dma_alloc/free_coherent.
> *Update changelog.
>
> drivers/scsi/ibmvscsi/ibmvfc.c | 16 ++++------------
> drivers/scsi/ibmvscsi/ibmvscsi.c | 29 +++++++++--------------------
> 2 files changed, 13 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
> index 1f1586ad48fe..6e95fd02fd25 100644
> --- a/drivers/scsi/ibmvscsi/ibmvfc.c
> +++ b/drivers/scsi/ibmvscsi/ibmvfc.c
> @@ -869,8 +869,8 @@ static void ibmvfc_free_queue(struct ibmvfc_host *vhost,
> {
> struct device *dev = vhost->dev;
>
> - dma_unmap_single(dev, queue->msg_token, PAGE_SIZE, DMA_BIDIRECTIONAL);
> - free_page((unsigned long)queue->msgs.handle);
> + dma_free_noncoherent(dev, PAGE_SIZE, queue->msgs.handle,
> + queue->msg_token, DMA_BIDIRECTIONAL);
> queue->msgs.handle = NULL;
>
> ibmvfc_free_event_pool(vhost, queue);
> @@ -5663,19 +5663,11 @@ static int ibmvfc_alloc_queue(struct ibmvfc_host *vhost,
> return -ENOMEM;
> }
>
> - queue->msgs.handle = (void *)get_zeroed_page(GFP_KERNEL);
> + queue->msgs.handle = dma_alloc_noncoherent(dev, PAGE_SIZE, &queue->msg_token,
> + DMA_BIDIRECTIONAL, GFP_KERNEL);
> if (!queue->msgs.handle)
> return -ENOMEM;
>
> - queue->msg_token = dma_map_single(dev, queue->msgs.handle, PAGE_SIZE,
> - DMA_BIDIRECTIONAL);
> -
> - if (dma_mapping_error(dev, queue->msg_token)) {
> - free_page((unsigned long)queue->msgs.handle);
> - queue->msgs.handle = NULL;
> - return -ENOMEM;
> - }
> -
> queue->cur = 0;
> queue->fmt = fmt;
> queue->size = PAGE_SIZE / fmt_size;
> diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
> index ea8e01f49cba..68409c298c74 100644
> --- a/drivers/scsi/ibmvscsi/ibmvscsi.c
> +++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
> @@ -151,10 +151,8 @@ static void ibmvscsi_release_crq_queue(struct crq_queue *queue,
> msleep(100);
> rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
> } while ((rc == H_BUSY) || (H_IS_LONG_BUSY(rc)));
> - dma_unmap_single(hostdata->dev,
> - queue->msg_token,
> - queue->size * sizeof(*queue->msgs), DMA_BIDIRECTIONAL);
> - free_page((unsigned long)queue->msgs);
> + dma_free_noncoherent(hostdata->dev, PAGE_SIZE,
> + queue->msgs, queue->msg_token, DMA_BIDIRECTIONAL);
> }
>
> /**
> @@ -331,18 +329,12 @@ static int ibmvscsi_init_crq_queue(struct crq_queue *queue,
> int retrc;
> struct vio_dev *vdev = to_vio_dev(hostdata->dev);
>
> - queue->msgs = (struct viosrp_crq *)get_zeroed_page(GFP_KERNEL);
> -
> - if (!queue->msgs)
> - goto malloc_failed;
> queue->size = PAGE_SIZE / sizeof(*queue->msgs);
> -
> - queue->msg_token = dma_map_single(hostdata->dev, queue->msgs,
> - queue->size * sizeof(*queue->msgs),
> - DMA_BIDIRECTIONAL);
> -
> - if (dma_mapping_error(hostdata->dev, queue->msg_token))
> - goto map_failed;
> + queue->msgs = dma_alloc_noncoherent(hostdata->dev,
> + PAGE_SIZE, &queue->msg_token,
> + DMA_BIDIRECTIONAL, GFP_KERNEL);
> + if (!queue->msg)
> + goto malloc_failed;
>
> gather_partition_info();
> set_adapter_info(hostdata);
> @@ -395,11 +387,8 @@ static int ibmvscsi_init_crq_queue(struct crq_queue *queue,
> rc = plpar_hcall_norets(H_FREE_CRQ, vdev->unit_address);
> } while ((rc == H_BUSY) || (H_IS_LONG_BUSY(rc)));
> reg_crq_failed:
> - dma_unmap_single(hostdata->dev,
> - queue->msg_token,
> - queue->size * sizeof(*queue->msgs), DMA_BIDIRECTIONAL);
> - map_failed:
> - free_page((unsigned long)queue->msgs);
> + dma_free_noncoherent(hostdata->dev, PAGE_SIZE, queue->msg,
> + queue->msg_token, DMA_BIDIRECTIONAL);
> malloc_failed:
> return -1;
> }
>