From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mark Lord <kernel@teksavvy.com>
Subject: Re: [BUG] libahci returns stale result tf much of the time.
Date: Fri, 24 Sep 2010 09:11:33 -0400
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To: Seed <seedrubbish@gmail.com>
Cc: Tejun Heo <htejun@gmail.com>, Jeff Garzik <jgarzik@pobox.com>, IDE/ATA development list <linux-ide@vger.kernel.org>

On 10-09-24 03:01 AM, Seed wrote:
> On Fri, Sep 24, 2010 at 4:27 PM, Mark Lord<kernel@teksavvy.com>  wrote:
>> The bug seems to be in the libahci code somewhere.
>
> ahci_qc_fill_rtf seems to be the function converting FIS to result_tf.
..

Yeah, that's as far as I got with it last night.
If you apply this patch (below), it makes the problem more "obvious",
though I still don't see exactly how that struct gets updated.

--- a/drivers/ata/libahci.c	2010-09-24 02:40:24.722887047 -0400
+++ b/drivers/ata/libahci.c	2010-09-24 09:10:21.761520099 -0400
@@ -1838,6 +1838,7 @@
  		d2h_fis += qc->dev->link->pmp * AHCI_RX_FIS_SZ;
  
  	ata_tf_from_fis(d2h_fis, &qc->result_tf);
+	memset(d2h_fis, 0xfd, AHCI_RX_FIS_SZ);
  	return true;
  }