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Date: Sat, 23 Apr 2011 03:08:04 -0400
From: Jeff Garzik <jgarzik@pobox.com>
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To: Jian Peng <jipeng2005@gmail.com>
CC: Tejun Heo <htejun@gmail.com>, linux-ide@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] libata: ahci_start_engine compliant to AHCI spec
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On 04/23/2011 02:58 AM, Jian Peng wrote:
> At the end of section 10.1 of AHCI spec (rev 1.3), it states
>
> Software shall not set PxCMD.ST to 1 until it is determined that
> a functoinal device is present on the port as determined by
> PxTFD.STS.BSY=0, PxTFD.STS.DRQ=0 and PxSSTS.DET=3h
>
> Even though most AHCI host controller works without this check,
> specific controller will fail under this condition.
>
> Signed-off-by: Jian Peng<jipeng2005@gmail.com>
> ---
>   drivers/ata/libahci.c |   21 +++++++++++++++++++++
>   1 files changed, 21 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/ata/libahci.c b/drivers/ata/libahci.c
> index 26d4523..83ed544 100644
> --- a/drivers/ata/libahci.c
> +++ b/drivers/ata/libahci.c
> @@ -539,6 +539,27 @@ void ahci_start_engine(struct ata_port *ap)
>   {
>   	void __iomem *port_mmio = ahci_port_base(ap);
>   	u32 tmp;
> +	u8 status;
> +
> +	status = readl(port_mmio + PORT_TFDATA)&  0xFF;
> +
> +	/*
> +	 * At end of section 10.1 of AHCI spec (rev 1.3), it states
> +	 * Software shall not set PxCMD.ST to 1 until it is determined
> +	 * that a functoinal device is present on the port as determined by
> +	 * PxTFD.STS.BSY=0, PxTFD.STS.DRQ=0 and PxSSTS.DET=3h
> +	 *
> +	 * Even though most AHCI host controllers work without this check,
> +	 * specific controller will fail under this condition
> +	 */
> +	if (status&  (ATA_BUSY | ATA_DRQ))
> +		return;
> +	else {
> +		ahci_scr_read(&ap->link, SCR_STATUS,&tmp);
> +
> +		if ((tmp&  0xf) != 0x3)
> +			return;
> +	}

Looks good, I'll get this queued up...