On 19/10/2022 11:15, Damien Le Moal wrote:
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.
Checked SATA-IO v3.5a. Software reset is explained in "11.4
Software reset protocol" and involves 2 things for the host to do:
DSR0: Software_reset_asserted, this state is entered if a Register Host
to Device FIS is received with the C bit in the FIS cleared to zero and
the SRST bit set to one in the Device Control register.
If in this state, the device begins its initialization and diagnostics
processing and awaits the clearing of the SRST bit.
DSR1: Execute_diagnostics, this state is entered if a Register Host to
Device FIS is received with the C bit in the FIS cleared to zero and the
SRST bit cleared to zero in the Device Control register.
If in this state, the device completes initialization and processing of
its diagnostics.
Which confirms what libahci is doing: essentially zeroing a tf with
ata_tf_init() and setting + resetting the SRST bit, sending the tf each
time.
Ah, so since the C bit is not set in hisi_sas_fill_ata_reset_cmd(), I
think that the command field is just ignored. Indeed, the spec says that
setting C and SRST together is invalid.
Thanks,
John
