Patchwork [1/1] libata: ahci_start_engine compliant to AHCI spec

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Submitter Jian Peng
Date April 23, 2011, 6:58 a.m.
Message ID <1303541890-14528-1-git-send-email-jipeng2005@gmail.com>
Download mbox | patch
Permalink /patch/92606/
State Not Applicable
Delegated to: David Miller
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Comments

Jian Peng - April 23, 2011, 6:58 a.m.
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(-)
Jeff Garzik - April 23, 2011, 7:08 a.m.
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...
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Tejun Heo - April 23, 2011, 2:40 p.m.
On Sat, Apr 23, 2011 at 8:58 AM, Jian Peng <jipeng2005@gmail.com> 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>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.
Sergei Shtylyov - April 25, 2011, 10:26 a.m.
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@gmail.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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Patch

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;
+	}
 
 	/* start DMA */
 	tmp = readl(port_mmio + PORT_CMD);