Hi,
 I just what to make it clear that this is not a bug of the Marvell's
PM, the sata specification (I'm looking at version 2.5) defines the
READ/WRITE PM registers to be extended commands, specifically, the
features HOB of the READ PM register defined to be RegNum[15:8].

saeed

On Thu, Feb 21, 2008 at 10:52 PM, Mark Lord [off-list ref] wrote:

Mark Lord wrote:
 > Tejun Heo wrote:
 >> Hello, Mark.
 >>
 >> Mark Lord wrote:
 >>> Tejun, I've added PMP to sata_mv, and am now trying to get it
 >>> to work with a Marvell PM attached.
 >>>
 >>> And the behaviour I see is very bizarre.
 >>>
 >>> After hard+soft resets, the PM signature is found,
 >>> and libata interrogates the PM registers.
 >>>
 >>> It successfully reads register 0, and then register 1.
 >>> But all subsequent registers read out (incorrectly) as zeros.
 ..

 Saeed has confirmed this behaviour with a SATA analyzer.
 The Marvell port-multiplier apparently likes to see clean HOB
 information when accessing PMP registers.

 Since sata_mv uses PIO shadow register access, this doesn't happen
 automatically, as it might in a more purely FIS-based driver (eg. ahci).

 One way to fix this is to flag these commands with ATA_TFLAG_LBA48,
 forcing libata to write out the HOB fields with known (zero) values.

 Signed-off-by: Saeed Bishara [off-list ref]
 Acked-by: Mark Lord [off-list ref]
 ---
  drivers/ata/libata-pmp.c |    4 ++--
  1 files changed, 2 insertions(+), 2 deletions(-)

 diff --git a/drivers/ata/libata-pmp.c b/drivers/ata/libata-pmp.c
 index caef2bb..d91f509 100644
 --- a/drivers/ata/libata-pmp.c
 +++ b/drivers/ata/libata-pmp.c
 @@ -35,7 +35,7 @@ static unsigned int sata_pmp_read(struct ata_link *link, int reg, u32 *r_val)
        ata_tf_init(pmp_dev, &tf);
        tf.command = ATA_CMD_PMP_READ;
        tf.protocol = ATA_PROT_NODATA;
 -       tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
 +       tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE | ATA_TFLAG_LBA48;
        tf.feature = reg;
        tf.device = link->pmp;

 @@ -71,7 +71,7 @@ static unsigned int sata_pmp_write(struct ata_link *link, int reg, u32 val)
        ata_tf_init(pmp_dev, &tf);
        tf.command = ATA_CMD_PMP_WRITE;
        tf.protocol = ATA_PROT_NODATA;
 -       tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE;
 +       tf.flags |= ATA_TFLAG_ISADDR | ATA_TFLAG_DEVICE | ATA_TFLAG_LBA48;
        tf.feature = reg;
        tf.device = link->pmp;
        tf.nsect = val & 0xff;
 -
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