linux-kernel - Re: [PATCH 1/7] scsi/bfa: use pcie_capability

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Date:	Tue, 3 Sep 2013 17:34:38 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Yijing Wang <wangyijing@...wei.com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Gavin Shan <shangw@...ux.vnet.ibm.com>,
	"James E.J. Bottomley" <JBottomley@...allels.com>,
	"David S. Miller" <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
	Hanjun Guo <guohanjun@...wei.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Anil Gurumurthy <agurumur@...cade.com>,
	Vijaya Mohan Guvva <vmohan@...cade.com>,
	linux-scsi@...r.kernel.org
Subject: Re: [PATCH 1/7] scsi/bfa: use pcie_capability_xxx to simplify code

On Tue, Sep 03, 2013 at 03:35:09PM +0800, Yijing Wang wrote:
> Pcie_capability_xxx() interfaces were introudced to
> simplify code to access PCIe Cap config space. And
> because PCI core saves the PCIe Cap offset in
> set_pcie_port_type() when device is enumerated.
> So we can use pci_is_pcie() instead.
> 
> Signed-off-by: Yijing Wang <wangyijing@...wei.com>
> Cc: Jiang Liu <jiang.liu@...wei.com>
> Cc: Anil Gurumurthy <agurumur@...cade.com>
> Cc: Vijaya Mohan Guvva <vmohan@...cade.com>
> Cc: "James E.J. Bottomley" <JBottomley@...allels.com>
> Cc: linux-scsi@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  drivers/scsi/bfa/bfad.c |    9 +++------
>  1 files changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/scsi/bfa/bfad.c b/drivers/scsi/bfa/bfad.c
> index 9611195..d726b81 100644
> --- a/drivers/scsi/bfa/bfad.c
> +++ b/drivers/scsi/bfa/bfad.c
> @@ -767,7 +767,6 @@ bfad_pci_init(struct pci_dev *pdev, struct bfad_s *bfad)
>  
>  	/* Adjust PCIe Maximum Read Request Size */
>  	if (pcie_max_read_reqsz > 0) {
> -		int pcie_cap_reg;
>  		u16 pcie_dev_ctl;
>  		u16 mask = 0xffff;
>  
> @@ -794,10 +793,8 @@ bfad_pci_init(struct pci_dev *pdev, struct bfad_s *bfad)
>  			break;
>  		}
>  
> -		pcie_cap_reg = pci_find_capability(pdev, PCI_CAP_ID_EXP);
> -		if (mask != 0xffff && pcie_cap_reg) {
> -			pcie_cap_reg += 0x08;
> -			pci_read_config_word(pdev, pcie_cap_reg, &pcie_dev_ctl);
> +		if (mask != 0xffff && pci_is_pcie(pdev)) {

Please move the pci_is_pcie() test up to the
"if (pcie_mas_read_reqsz ..." statement.  There's no point in doing
the switch statement if this isn't a PCIe device.

> +			pcie_capability_read_word(pdev, PCI_EXP_DEVCTL, &pcie_dev_ctl);
>  			if ((pcie_dev_ctl & 0x7000) != mask) {
>  				printk(KERN_WARNING "BFA[%s]: "
>  				"pcie_max_read_request_size is %d, "
> @@ -806,7 +803,7 @@ bfad_pci_init(struct pci_dev *pdev, struct bfad_s *bfad)
>  				pcie_max_read_reqsz);
>  
>  				pcie_dev_ctl &= ~0x7000;
> -				pci_write_config_word(pdev, pcie_cap_reg,
> +				pcie_capability_write_word(pdev, PCI_EXP_DEVCTL,
>  						pcie_dev_ctl | mask);

Please rework this to use pcie_set_readrq() instead of writing
the capability directly.  If we write the capability directly, we
risk writing a value that is incompatible with the MPS
configuration done by the PCI core.

>  			}
>  		}
> -- 
> 1.7.1
> 
> 
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