From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH v3 1/2] libahci: Add support to handle HOST_IRQ_STAT as
 edge trigger latch.
Date: Mon, 4 May 2015 11:47:26 -0400
Message-ID: <20150504154726.GA1971@htj.duckdns.org>
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To: Suman Tripathi <stripathi@apm.com>
Cc: olof@lixom.net, arnd@arndb.de, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, mlangsdo@redhat.com, jcm@redhat.com, patches@apm.com
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On Sun, May 03, 2015 at 09:03:39PM +0530, Suman Tripathi wrote:
> This patch adds the support to handle HOST_IRQ_STAT as edge trigger
> latch.
...
> +	/*
> +	 * HOST_IRQ_STAT behaves as edge trigger latch. When HOST_IRQ_STAT
> +	 * detects a egde from PORT_IRQ_STAT, it happens to loose interrupts
> +	 * when interrupts are triggered from both ports. So handling of
> +	 * the residual interrupt is required.
> +	 */
> +	if (hpriv->flags & AHCI_HFLAG_EDGE_TRIG_IRQ) {
> +		for (i = 0; i < host->n_ports; i++) {
> +			struct ata_port *ap;
> +
> +			ap = host->ports[i];
> +			if (ap) {
> +				ahci_port_intr(ap);
> +				VPRINTK("Residual irq from port %u\n", i);
> +			}
> +			handled = 1;
> +		}
> +	}

This is kinda gross.  The right thing do is clearing irq stat
registers before handling the events, right?  That shouldn't be too
difficult to implement.  Create a separate set of irq functions which
clear irqs before processing rather than after.

Thanks.

-- 
tejun