Re: libata and software reset

[John Garry <john.garry@huawei.com>]

On 19/10/2022 06:04, Damien Le Moal wrote:
> On 10/19/22 14:03, Damien Le Moal wrote:
>> On 10/18/22 22:24, John Garry wrote:
>>> Hi guys,
>>>
>>> In the hisi_sas driver there are times in which we need to issue an ATA
>>> software reset. For this we use hisi_sas_softreset_ata_disk() ->
>>> sas_execute_ata_cmd() -> sas_execute_tmf(), which uses libsas "slow
>>> task" mechanism to issue the command.
>> Something is wrong here... The reset command sent by that function is
>> for ATAPI (DEVICE RESET command). There is no device reset command for
>> SATA disks following the ACS standard.

Yeah, that looks wrong.

>>
>> So hisi_sas_softreset_ata_disk() seems totally bogus to me, unless you
>> have a CD/DVD drive connected to the HBA:)

Sure

>>
>> This is why the softreset function is a port operation defined by LLDs.
>> How you reset the device depends on the adapter. E.g., for AHCI, you
>> need to send a host2device FIS with the software reset bit set.

This would be quite a standard method, right?

> See: ahci_do_softreset() for AHCI.

For ahci_do_softreset(), do you just implicitly use ATA_CMD_NOP as the 
command?

For hisi_sas, maybe ATA_CMD_DEV_RESET is silently ignored when issued 
for a SATA disk, but having SRST set/unset still takes effect (and that 
is how it still works). I need to check on that.

Thanks,
John