[PATCH] virito-pci-modern: Remove useless DMA-32 fallback configuration

[PATCH] virito-pci-modern: Remove useless DMA-32 fallback configuration

[cgel.zte]

From: Minghao Chi <chi.minghao@zte.com.cn>

As stated in [1], dma_set_mask() with a 64-bit mask will never fail if
dev->dma_mask is non-NULL.
So, if it fails, the 32 bits case will also fail for the same reason.

Simplify code and remove some dead code accordingly.

[1]: https://lkml.org/lkml/2021/6/7/398

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
---
 drivers/virtio/virtio_pci_modern_dev.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
index e8b3ff2b9fbc..dff0b15a239d 100644
--- a/drivers/virtio/virtio_pci_modern_dev.c
+++ b/drivers/virtio/virtio_pci_modern_dev.c
@@ -255,9 +255,6 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
 	}
 
 	err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
-	if (err)
-		err = dma_set_mask_and_coherent(&pci_dev->dev,
-						DMA_BIT_MASK(32));
 	if (err)
 		dev_warn(&pci_dev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.\n");
 
-- 
2.25.1

Re: [PATCH] virito-pci-modern: Remove useless DMA-32 fallback configuration

[Jason Wang]

On Fri, Mar 18, 2022 at 8:59 AM <cgel.zte@gmail.com> wrote:
>
> From: Minghao Chi <chi.minghao@zte.com.cn>
>
> As stated in [1], dma_set_mask() with a 64-bit mask will never fail if
> dev->dma_mask is non-NULL.
> So, if it fails, the 32 bits case will also fail for the same reason.
>
> Simplify code and remove some dead code accordingly.
>
> [1]: https://lkml.org/lkml/2021/6/7/398
>
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
> ---
>  drivers/virtio/virtio_pci_modern_dev.c | 3 ---
>  1 file changed, 3 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
> index e8b3ff2b9fbc..dff0b15a239d 100644
> --- a/drivers/virtio/virtio_pci_modern_dev.c
> +++ b/drivers/virtio/virtio_pci_modern_dev.c
> @@ -255,9 +255,6 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
>         }
>
>         err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
> -       if (err)
> -               err = dma_set_mask_and_coherent(&pci_dev->dev,
> -                                               DMA_BIT_MASK(32));

So we had:

        if (!dev->dma_mask || !dma_supported(dev, mask))
                return -EIO;

in dma_set_mask(), any reason dma_supported() can't be false here?

Thanks

>         if (err)
>                 dev_warn(&pci_dev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.\n");
>
> --
> 2.25.1
>

Re: [PATCH] virito-pci-modern: Remove useless DMA-32 fallback configuration

[Michael S. Tsirkin]

Typo in subj, and pls make subject match actual file name (_ not -).


On Fri, Mar 18, 2022 at 12:58:58AM +0000, cgel.zte@gmail.com wrote:
> From: Minghao Chi <chi.minghao@zte.com.cn>
> 
> As stated in [1], dma_set_mask() with a 64-bit mask will never fail if
> dev->dma_mask is non-NULL.
> So, if it fails, the 32 bits case will also fail for the same reason.
> 
> Simplify code and remove some dead code accordingly.
> 
> [1]: https://lkml.org/lkml/2021/6/7/398
> 
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Signed-off-by: Minghao Chi <chi.minghao@zte.com.cn>
> ---
>  drivers/virtio/virtio_pci_modern_dev.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_pci_modern_dev.c b/drivers/virtio/virtio_pci_modern_dev.c
> index e8b3ff2b9fbc..dff0b15a239d 100644
> --- a/drivers/virtio/virtio_pci_modern_dev.c
> +++ b/drivers/virtio/virtio_pci_modern_dev.c
> @@ -255,9 +255,6 @@ int vp_modern_probe(struct virtio_pci_modern_device *mdev)
>  	}
>  
>  	err = dma_set_mask_and_coherent(&pci_dev->dev, DMA_BIT_MASK(64));
> -	if (err)
> -		err = dma_set_mask_and_coherent(&pci_dev->dev,
> -						DMA_BIT_MASK(32));
>  	if (err)
>  		dev_warn(&pci_dev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.\n");
>  
> -- 
> 2.25.1