2022-01-09 18:23:25

by Christophe JAILLET

Subject: [PATCH] e1000e: Remove useless DMA-32 fallback configuration

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

So, if dma_set_mask_and_coherent() succeeds, 'pci_using_dac' is known to be
1.

Simplify code and remove some dead code accordingly.

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

Signed-off-by: Christophe JAILLET <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Alexander Lobakin <[email protected]>
---
drivers/net/ethernet/intel/e1000e/netdev.c | 22 +++++++---------------
1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
index 635a95927e93..4f6ee5c44f75 100644
--- a/drivers/net/ethernet/intel/e1000e/netdev.c
+++ b/drivers/net/ethernet/intel/e1000e/netdev.c
@@ -7385,9 +7385,9 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
resource_size_t flash_start, flash_len;
static int cards_found;
u16 aspm_disable_flag = 0;
- int bars, i, err, pci_using_dac;
u16 eeprom_data = 0;
u16 eeprom_apme_mask = E1000_EEPROM_APME;
+ int bars, i, err;
s32 ret_val = 0;

if (ei->flags2 & FLAG2_DISABLE_ASPM_L0S)
@@ -7401,17 +7401,11 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
if (err)
return err;

- pci_using_dac = 0;
err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
- if (!err) {
- pci_using_dac = 1;
- } else {
- err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
- if (err) {
- dev_err(&pdev->dev,
- "No usable DMA configuration, aborting\n");
- goto err_dma;
- }
+ if (err) {
+ dev_err(&pdev->dev,
+ "No usable DMA configuration, aborting\n");
+ goto err_dma;
}

bars = pci_select_bars(pdev, IORESOURCE_MEM);
@@ -7547,10 +7541,8 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)

netdev->priv_flags |= IFF_UNICAST_FLT;

- if (pci_using_dac) {
- netdev->features |= NETIF_F_HIGHDMA;
- netdev->vlan_features |= NETIF_F_HIGHDMA;
- }
+ netdev->features |= NETIF_F_HIGHDMA;
+ netdev->vlan_features |= NETIF_F_HIGHDMA;

/* MTU range: 68 - max_hw_frame_size */
netdev->min_mtu = ETH_MIN_MTU;
--
2.32.0

2022-01-30 23:41:16

by Sasha Neftin

Subject: Re: [Intel-wired-lan] [PATCH] e1000e: Remove useless DMA-32 fallback configuration

On 1/9/2022 20:23, Christophe JAILLET wrote:
> As stated in [1], dma_set_mask() with a 64-bit mask never fails if
> dev->dma_mask is non-NULL.
> So, if it fails, the 32 bits case will also fail for the same reason.
>
> So, if dma_set_mask_and_coherent() succeeds, 'pci_using_dac' is known to be
> 1.
>
> Simplify code and remove some dead code accordingly.
>
> [1]: https://lkml.org/lkml/2021/6/7/398
>
> Signed-off-by: Christophe JAILLET <[email protected]>
> Reviewed-by: Christoph Hellwig <[email protected]>
> Reviewed-by: Alexander Lobakin <[email protected]>
> ---
> drivers/net/ethernet/intel/e1000e/netdev.c | 22 +++++++---------------
> 1 file changed, 7 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
> index 635a95927e93..4f6ee5c44f75 100644
> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
> @@ -7385,9 +7385,9 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> resource_size_t flash_start, flash_len;
> static int cards_found;
> u16 aspm_disable_flag = 0;
> - int bars, i, err, pci_using_dac;
> u16 eeprom_data = 0;
> u16 eeprom_apme_mask = E1000_EEPROM_APME;
> + int bars, i, err;
> s32 ret_val = 0;
>
> if (ei->flags2 & FLAG2_DISABLE_ASPM_L0S)
> @@ -7401,17 +7401,11 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
> if (err)
> return err;
>
> - pci_using_dac = 0;
> err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
> - if (!err) {
> - pci_using_dac = 1;
> - } else {
> - err = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
> - if (err) {
> - dev_err(&pdev->dev,
> - "No usable DMA configuration, aborting\n");
> - goto err_dma;
> - }
> + if (err) {
> + dev_err(&pdev->dev,
> + "No usable DMA configuration, aborting\n");
> + goto err_dma;
> }
>
> bars = pci_select_bars(pdev, IORESOURCE_MEM);
> @@ -7547,10 +7541,8 @@ static int e1000_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>
> netdev->priv_flags |= IFF_UNICAST_FLT;
>
> - if (pci_using_dac) {
> - netdev->features |= NETIF_F_HIGHDMA;
> - netdev->vlan_features |= NETIF_F_HIGHDMA;
> - }
> + netdev->features |= NETIF_F_HIGHDMA;
> + netdev->vlan_features |= NETIF_F_HIGHDMA;
>
> /* MTU range: 68 - max_hw_frame_size */
> netdev->min_mtu = ETH_MIN_MTU;
Thank you Christophe
Acked-by: Sasha Neftin <[email protected]>