linux-kernel - Re: [PATCH] OMAP: HSMMC: Do not enable buffer ready interrupt if using DMA

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Date:	Tue, 5 May 2009 12:57:21 +0300
From:	Jarkko Lavinen <jarkko.lavinen@...ia.com>
To:	"ext Gadiyar, Anand" <gadiyar@...com>
Cc:	"pierre@...man.eu" <pierre@...man.eu>,
	Tony Lindgren <tony@...mide.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: [PATCH] OMAP: HSMMC: Do not enable buffer ready interrupt if
	using DMA

On Tue, Apr 21, 2009 at 09:39:22AM +0200, ext Gadiyar, Anand wrote:
> From: Anand Gadiyar <gadiyar@...com>
> 
> OMAP: HSMMC: Do not enable buffer ready interrupt if using DMA
> 
> This considerably reduces the number of interrupts during a transfer
> and ought to result in some power saving.

I tried the patch with reading from the raw mmc block device to
/dev/null with dd (with bs 32k and 1M).  I cannot see any
difference in interrupt count from /proc/interrupts or in read
speed. At least the patch works. Cpu was 34340es3.

I also trid without the patch just disabling the Buffer
Read/write Ready bits from INT_EN_MASK which is then written to
both MMCHS_IE and MMCHS_ISE.  Still no change in read speed nor
mmc irq count.

Cheers
Jarkko Lavinen
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