linux-kernel - Re: [PATCH v2] AHCI: Add generic MSI-X interrupt support to SATA PCI driver

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Message-ID: <20150513174640.GZ11388@htj.duckdns.org>
Date:	Wed, 13 May 2015 13:46:40 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Robert Richter <robert.richter@...iumnetworks.com>
Cc:	Robert Richter <rric@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Sunil Goutham <sgoutham@...ium.com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-ide@...r.kernel.org, Alexander Gordeev <agordeev@...hat.com>
Subject: Re: [PATCH v2] AHCI: Add generic MSI-X interrupt support to SATA PCI
 driver

Hello, Robert.

On Wed, May 13, 2015 at 07:28:28PM +0200, Robert Richter wrote:
> > > This looks not very useful to do. Since irq is used only a single
> > > time, there is no reason to store it in the host's data structure. It
> > 
> > Doesn't really matter tho.
> 
> Since ahci_host_activate() is EXPORT_SYMBOL_GPL I really have concerns
> changing the i/f. But I will send you a patch for this.

It doesn't matter.  Please go ahead and change it.

> > Let's start with why we're doing this in the first place.
> 
> Right, the sata controller is connected to a pci ecam controller, both
> are on an SoC together with the processor. There are no external pci
> ports for the connection of external devices. Since all pci devices on
> the chip support msi-x, the controller is only capable to handle this
> and not INTx nor MSI. So for enabling of the sata hc we need msix
> support.

I see.  If you can get hold of an ahci controller which actually can
do multi-irq msix, it'd be the best.  If not, let's make it super
clear that this is a special case and use it as the last resort (which
also clers up the warning issue).

Thanks.

-- 
tejun
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