linux-kernel - Re: [PATCH v4 3/3] AHCI: Add generic MSI-X interrupt support to SATA PCI driver

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Message-ID: <20150603054422.GD20091@mtj.duckdns.org>
Date:	Wed, 3 Jun 2015 14:44:22 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Robert Richter <rric@...nel.org>
Cc:	Sunil Goutham <sgoutham@...ium.com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Robert Richter <rrichter@...ium.com>
Subject: Re: [PATCH v4 3/3] AHCI: Add generic MSI-X interrupt support to SATA
 PCI driver

Hello, Robert.

Maybe qualifying the subject that it's only for single IRQ would be a
good idea?

> @@ -52,6 +53,7 @@
>  
>  enum {
>  	AHCI_PCI_BAR_STA2X11	= 0,
> +	AHCI_PCI_BAR_CAVIUM	= 0,
>  	AHCI_PCI_BAR_ENMOTUS	= 2,
>  	AHCI_PCI_BAR_STANDARD	= 5,

I thought I already asked but please separate out CAVIUM specific
changes from msix implementation and follow up with why cavium depends
on msix support.

> +static int ahci_init_msix(struct pci_dev *pdev, unsigned int n_ports,
> +			  struct ahci_host_priv *hpriv)
> +{

Please add a comment describing that it's for single msix only and why
that'd be necessary for certain controllers.

...
> +	/*
> +	 * Per-port msix interrupts are not supported. Assume single
> +	 * port interrupts for:
> +	 *
> +	 *  n_ports == 1, or
> +	 *  nvec < n_ports.
> +	 *
> +	 * We also need to check for n_ports != 0 which is implicitly
> +	 * covered here since nvec > 0.
> +	 */
> +	if (n_ports != 1 && nvec >= n_ports) {
> +		rc = -ENOSYS;
> +		goto fail;
> +	}

Didn't I ask this one too the last time?  Can you explain why we can't
initialize single IRQ mode if nvec >= n_ports?

> @@ -1260,6 +1339,10 @@ static int ahci_init_interrupts(struct pci_dev *pdev, unsigned int n_ports,
>  	if (nvec >= 0)
>  		return nvec;
>  
> +	nvec = ahci_init_msix(pdev, n_ports, hpriv);
> +	if (nvec >= 0)
> +		return nvec;

Please add a comment explaining why we're doing msix after msi.

Thanks.

-- 
tejun
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