netdev - Re: [PATCH v2 net-next] pds_core: remove redundant pci_clear

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Date: Thu, 17 Aug 2023 08:55:22 -0700
From: "Nelson, Shannon" <shannon.nelson@....com>
To: Yu Liao <liaoyu15@...wei.com>, netdev@...r.kernel.org,
 davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
 pabeni@...hat.com, leon@...nel.org
Cc: liwei391@...wei.com
Subject: Re: [PATCH v2 net-next] pds_core: remove redundant pci_clear_master()

On 8/16/2023 7:57 PM, Yu Liao wrote:
> 
> do_pci_disable_device() disable PCI bus-mastering as following:
> static void do_pci_disable_device(struct pci_dev *dev)
> {
>                  u16 pci_command;
> 
>                  pci_read_config_word(dev, PCI_COMMAND, &pci_command);
>                  if (pci_command & PCI_COMMAND_MASTER) {
>                                  pci_command &= ~PCI_COMMAND_MASTER;
>                                  pci_write_config_word(dev, PCI_COMMAND, pci_command);
>                  }
> 
>                  pcibios_disable_device(dev);
> }
> And pci_disable_device() sets dev->is_busmaster to 0.
> 
> pci_enable_device() is called only once before calling to
> pci_disable_device() and such pci_clear_master() is not needed. So remove
> redundant pci_clear_master().
> 
> Also rename goto label 'err_out_clear_master' to 'err_out_disable_device'.
> 
> Signed-off-by: Yu Liao <liaoyu15@...wei.com>

Acked-by: Shannon Nelson <shannon.nelson@....com>


> ---
> v1 -> v2:
> - add explanation why pci_disable_device() disables PCI bus-mastering
> - rename goto label 'err_out_clear_master' to 'err_out_disable_device'
> ---
>   drivers/net/ethernet/amd/pds_core/main.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/amd/pds_core/main.c b/drivers/net/ethernet/amd/pds_core/main.c
> index 672757932246..3a45bf474a19 100644
> --- a/drivers/net/ethernet/amd/pds_core/main.c
> +++ b/drivers/net/ethernet/amd/pds_core/main.c
> @@ -367,14 +367,13 @@ static int pdsc_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>                  err = pdsc_init_vf(pdsc);
>          if (err) {
>                  dev_err(dev, "Cannot init device: %pe\n", ERR_PTR(err));
> -               goto err_out_clear_master;
> +               goto err_out_disable_device;
>          }
> 
>          clear_bit(PDSC_S_INITING_DRIVER, &pdsc->state);
>          return 0;
> 
> -err_out_clear_master:
> -       pci_clear_master(pdev);
> +err_out_disable_device:
>          pci_disable_device(pdev);
>   err_out_free_ida:
>          ida_free(&pdsc_ida, pdsc->uid);
> @@ -439,7 +438,6 @@ static void pdsc_remove(struct pci_dev *pdev)
>                  pci_release_regions(pdev);
>          }
> 
> -       pci_clear_master(pdev);
>          pci_disable_device(pdev);
> 
>          ida_free(&pdsc_ida, pdsc->uid);
> --
> 2.25.1
>