linux-kernel - Re: [PATCH 1/1] libata: ahci_start

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Date:	Mon, 25 Apr 2011 14:26:17 +0400
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	Jian Peng <jipeng2005@...il.com>
CC:	Jeff Garzik <jgarzik@...ox.com>, Tejun Heo <htejun@...il.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] libata: ahci_start_engine compliant to AHCI spec

Hello.

On 23-04-2011 10:58, 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,

    "Most" requires plural noun, no?

> specific controller will fail under this condition.

> Signed-off-by: Jian Peng<jipeng2005@...il.com>
[...]

> 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;

    Masking is not necessary.

> +
> +	/*
> +	 * 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,

    Same about grammar here.

> +	 * specific controller will fail under this condition
> +	 */
> +	if (status&  (ATA_BUSY | ATA_DRQ))
> +		return;
> +	else {

    {} should be used on both branches, according to CodingStyle.

WBR, Sergei
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