Re: [PATCH 1/2] libata: allow sata_sil24 to opt-out of tag ordered submission

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Hello.

On 1/17/2015 2:13 AM, Dan Williams wrote:

> Ronny reports: https://bugzilla.kernel.org/show_bug.cgi?id=87101
>      "Since commit 8a4aeec8d "libata/ahci: accommodate tag ordered
>      controllers" the access to the harddisk on the first SATA-port is
>      failing on its first access. The access to the harddisk on the
>      second port is working normal.

>      When reverting the above commit, access to both harddisks is working
>      fine again."

> Maintain tag ordered submission as the default, but allow sata_sil24 to
> continue with the old behavior.

> Cc: <stable@vger.kernel.org>
> Cc: Tejun Heo <tj@kernel.org>
> Reported-by: Ronny Hegewald <Ronny.Hegewald@online.de>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>   drivers/ata/libata-core.c |    5 ++++-
>   drivers/ata/sata_sil24.c  |    2 +-
>   include/linux/libata.h    |    1 +
>   3 files changed, 6 insertions(+), 2 deletions(-)

> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index 5c84fb5c3372..e2085d4b5b93 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -4748,7 +4748,10 @@ static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)
>   		return NULL;
>
>   	for (i = 0, tag = ap->last_tag + 1; i < max_queue; i++, tag++) {
> -		tag = tag < max_queue ? tag : 0;
> +		if (ap->flags & ATA_FLAG_LOWTAG)
> +			tag = i;
> +		else
> +			tag = tag < max_queue ? tag : 0;

    Ugh, this is clear abuse of the ?: operator... Why not simply:

		else if (tag >= max_queue)
			tag = 0;

[...]

MBR, Sergei