From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kevin Hao Subject: [PATCH v3] libata: support the ata host which implements a queue depth less than 32 Date: Fri, 11 Jul 2014 14:10:26 +0800 Message-ID: <1405059026-18673-1-git-send-email-haokexin@gmail.com> Return-path: Received: from mail-pa0-f45.google.com ([209.85.220.45]:58647 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751517AbaGKGLL (ORCPT ); Fri, 11 Jul 2014 02:11:11 -0400 Received: by mail-pa0-f45.google.com with SMTP id rd3so875716pab.4 for ; Thu, 10 Jul 2014 23:11:11 -0700 (PDT) Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: linux-ide@vger.kernel.org Cc: Tejun Heo , Dan Williams The sata on fsl mpc8315e is broken after the commit 8a4aeec8d2d6 ("libata/ahci: accommodate tag ordered controllers"). The reason is that the ata controller on this SoC only implement a queue depth of 16. When issuing the commands in tag order, all the commands in tag 16 ~ 31 are mapped to tag 0 unconditionally and then causes the sata malfunction. It makes no senses to use a 32 queue in software while the hardware has less queue depth. So consider the queue depth implemented by the hardware when requesting a command tag. Fixes: 8a4aeec8d2d6 ("libata/ahci: accommodate tag ordered controllers") Cc: stable@vger.kernel.org Signed-off-by: Kevin Hao --- v3: Use ap->scsi_host->can_queue for the queue depth implemented by hardware. Patch 2 in v2 is also dropped due to this change. v2: Remove the changes for the ata tag helper functions Hi Tejun, I didn't get explicit objection for the codes at http://marc.info/?l=linux-ide&m=140478830920334&w=2 So I assume that you are OK wit it. The code in this patch is the same as that, just add the commit log. drivers/ata/libata-core.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c index 8f3043165048..4792fea79acf 100644 --- a/drivers/ata/libata-core.c +++ b/drivers/ata/libata-core.c @@ -4728,14 +4728,17 @@ void swap_buf_le16(u16 *buf, unsigned int buf_words) static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap) { struct ata_queued_cmd *qc = NULL; - unsigned int i, tag; + unsigned int i, tag, max_queue; + + max_queue = ap->scsi_host->can_queue; + WARN_ON_ONCE(max_queue > ATA_MAX_QUEUE); /* no command while frozen */ if (unlikely(ap->pflags & ATA_PFLAG_FROZEN)) return NULL; - for (i = 0; i < ATA_MAX_QUEUE; i++) { - tag = (i + ap->last_tag + 1) % ATA_MAX_QUEUE; + for (i = 0, tag = ap->last_tag + 1; i < max_queue; i++, tag++) { + tag = tag < max_queue ? tag : 0; /* the last tag is reserved for internal command. */ if (tag == ATA_TAG_INTERNAL) -- 1.9.3