sata_fsl: add workaround for data length mismatch on freescale V2 controller

The freescale V2 SATA controller checks if the received data length matches
the programmed length 'ttl', if not, it assumes that this is an error.
In ATAPI, the 'ttl' is based on max allocation length and not the actual
data transfer length, controller will raise 'DLM' (Data length Mismatch)
error bit in Hstatus register. Along with 'DLM', DE (Device error) and
FE (fatal Error) bits are also set in Hstatus register, 'E' (Internal Error)
bit is set in Serror register and CE (Command Error) and DE (Device error)
registers have the corresponding bit set. In this condition, we need to
clear errors in following way: in the service routine, based on 'DLM' flag,
HCONTROL[27] operation clears Hstatus, CE and DE registers, clear Serror
register.

Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: Anju Bhartiya <Anju.Bhartiya@freescale.com>
---
 drivers/ata/sata_fsl.c |   48 +++++++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 43 insertions(+), 5 deletions(-)

> The freescale V2 SATA controller checks
> if the received data length matches
> the programmed length 'ttl', if not,
> it assumes that this is an error.
...

Can you tell us exactly what
"The freescale V2 SATA controller" is,
and what versions of what devices contain it?

Thanks,
Clive

> +	/* Read command completed register */
> +	done_mask = ioread32(hcr_base + CC);
> +
> +	if (host_priv->quirks & SATA_FSL_QUIRK_V2_ERRATA) {
> +		if (unlikely(hstatus & INT_ON_DATA_LENGTH_MISMATCH)) {
> +			for (tag = 0; tag < ATA_MAX_QUEUE; tag++) {
> +				qc = ata_qc_from_tag(ap, tag);
> +				if (qc && ata_is_atapi(qc->tf.protocol))
{
> +					atapi_flag = 1;
> +					break;
> +				}
> +			}
> +		}
> +	}
> +
> +	/* Workaround for data length mismatch errata */
> +	if (atapi_flag) {

Seems to me like the conditionals for this code are all
in the wrong order - adding code to the normal path.

The whole lot should probably be inside:
	if (unlikely(hstatus & INT_ON_DATA_LENGTH_MISMATCH)) {
and the 'atapi_flag' boolean removed.

I also wonder it this is worthy of an actual quirk?
Might be worth doing anyway.

	David

> -----Original Message-----
> From: David Laight [mailto:David.Laight@ACULAB.COM]
> Sent: Tuesday, September 04, 2012 10:51 PM
> To: Xie Shaohui-B21989; jgarzik@pobox.com; linux-ide@vger.kernel.org
> Cc: linuxppc-dev@lists.ozlabs.org; linux-kernel@vger.kernel.org; Bhartiya
> Anju-B07263
> Subject: RE: [PATCH] sata_fsl: add workaround for data length mismatch on
> freescale V2 controller
> 
> > +	/* Read command completed register */
> > +	done_mask = ioread32(hcr_base + CC);
> > +
> > +	if (host_priv->quirks & SATA_FSL_QUIRK_V2_ERRATA) {
> > +		if (unlikely(hstatus & INT_ON_DATA_LENGTH_MISMATCH)) {
> > +			for (tag = 0; tag < ATA_MAX_QUEUE; tag++) {
> > +				qc = ata_qc_from_tag(ap, tag);
> > +				if (qc && ata_is_atapi(qc->tf.protocol))
> {
> > +					atapi_flag = 1;
> > +					break;
> > +				}
> > +			}
> > +		}
> > +	}
> > +
> > +	/* Workaround for data length mismatch errata */
> > +	if (atapi_flag) {
> 
> Seems to me like the conditionals for this code are all in the wrong
> order - adding code to the normal path.
> 
> The whole lot should probably be inside:
> 	if (unlikely(hstatus & INT_ON_DATA_LENGTH_MISMATCH)) { and the
> 'atapi_flag' boolean removed.
[S.H] OK. But I need to move the "done_mask = ioread32(hcr_base + CC);" before these codes,
 because these codes will clean command completed register.

> 
> I also wonder it this is worthy of an actual quirk?
> Might be worth doing anyway.
[S.H] The quirk is useful for our internal use(there is another errata but got fixed by silicon upgrade),
but you are right it's worth doing anyway in upstream, since the upstream code only handles this errata.

Best Regards, 
Shaohui Xie