linux-kernel - Re: [PATCH 3/3] ntb: intel: Remove redundant pci_clear

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Date:   Thu, 23 Mar 2023 09:51:38 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     Cai Huoqing <cai.huoqing@...ux.dev>
Cc:     Sanjay R Mehta <sanju.mehta@....com>,
        Shyam Sundar S K <Shyam-sundar.S-k@....com>,
        Jon Mason <jdmason@...zu.us>, Allen Hubbe <allenbh@...il.com>,
        Frank Li <Frank.Li@....com>, ntb@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] ntb: intel: Remove redundant pci_clear_master



On 3/23/23 4:53 AM, Cai Huoqing wrote:
> Remove pci_clear_master to simplify the code,
> the bus-mastering is also cleared in do_pci_disable_device,
> like this:
> ./drivers/pci/pci.c:2197
> 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 dev->is_busmaster is set to 0 in pci_disable_device.
> 
> Signed-off-by: Cai Huoqing <cai.huoqing@...ux.dev>

Acked-by: Dave Jiang <dave.jiang@...el.com>

> ---
>   drivers/ntb/hw/intel/ntb_hw_gen1.c | 2 --
>   1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/ntb/hw/intel/ntb_hw_gen1.c b/drivers/ntb/hw/intel/ntb_hw_gen1.c
> index 60a4ebc7bf35..9ab836d0d4f1 100644
> --- a/drivers/ntb/hw/intel/ntb_hw_gen1.c
> +++ b/drivers/ntb/hw/intel/ntb_hw_gen1.c
> @@ -1791,7 +1791,6 @@ static int intel_ntb_init_pci(struct intel_ntb_dev *ndev, struct pci_dev *pdev)
>   
>   err_mmio:
>   err_dma_mask:
> -	pci_clear_master(pdev);
>   	pci_release_regions(pdev);
>   err_pci_regions:
>   	pci_disable_device(pdev);
> @@ -1808,7 +1807,6 @@ static void intel_ntb_deinit_pci(struct intel_ntb_dev *ndev)
>   		pci_iounmap(pdev, ndev->peer_mmio);
>   	pci_iounmap(pdev, ndev->self_mmio);
>   
> -	pci_clear_master(pdev);
>   	pci_release_regions(pdev);
>   	pci_disable_device(pdev);
>   	pci_set_drvdata(pdev, NULL);