linux-kernel - Re: [PATCH 3/7] ahci: Use new interfaces for MSI/MSI-X enablement

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Message-ID: <20140113191220.GA6525@google.com>
Date:	Mon, 13 Jan 2014 12:12:20 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Alexander Gordeev <agordeev@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	linux-ide@...r.kernel.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 3/7] ahci: Use new interfaces for MSI/MSI-X enablement

On Tue, Jan 07, 2014 at 07:05:38PM +0100, Alexander Gordeev wrote:
> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
> ---
>  drivers/ata/ahci.c |   15 ++++++---------
>  1 files changed, 6 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
> index 8516f4d..cfdb079 100644
> --- a/drivers/ata/ahci.c
> +++ b/drivers/ata/ahci.c
> @@ -1098,13 +1098,13 @@ static inline void ahci_gtf_filter_workaround(struct ata_host *host)
>  int ahci_init_interrupts(struct pci_dev *pdev, unsigned int n_ports,
>  			 struct ahci_host_priv *hpriv)
>  {
> -	int rc, nvec;
> +	int nvec;
>  
>  	if (hpriv->flags & AHCI_HFLAG_NO_MSI)
>  		goto intx;
>  
> -	rc = pci_msi_vec_count(pdev);
> -	if (rc < 0)
> +	nvec = pci_msi_vec_count(pdev);
> +	if (nvec < 0)
>  		goto intx;
>  
>  	/*
> @@ -1112,19 +1112,16 @@ int ahci_init_interrupts(struct pci_dev *pdev, unsigned int n_ports,
>  	 * Message mode could be enforced. In this case assume that advantage
>  	 * of multipe MSIs is negated and use single MSI mode instead.
>  	 */
> -	if (rc < n_ports)
> +	if (nvec < n_ports)
>  		goto single_msi;
>  
> -	nvec = rc;
> -	rc = pci_enable_msi_block(pdev, nvec);
> -	if (rc)
> +	if (pci_enable_msi_range(pdev, nvec, nvec) < 0)
>  		goto intx;
>  
>  	return nvec;
>  
>  single_msi:
> -	rc = pci_enable_msi(pdev);
> -	if (rc)
> +	if (pci_enable_msi_range(pdev, 1, 1) < 0)

This part doesn't seem like an improvement.  There are a hundred or so
callers of pci_enable_msi() that only want a single MSI.  Is there any
benefit in changing them to use pci_enable_msi_range()?

I guess I agreed (maybe even suggested) to deprecate pci_enable_msi(),
but it doesn't suffer from the tri-state return value problem, and I'm
having second thoughts.

>  		goto intx;
>  	return 1;
>  
> -- 
> 1.7.7.6
> 
> --
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