Mark Lord wrote:
ATA/SATA drives can be set to not spinup automatically at power-on,
for use in staggered spin-up applications where frying power supplies
is to be avoided.
These drives may return incomplete IDENTIFY responses
until they have been spun-up first by the device driver.
There are two ways this happens, and the drive lets us know
which it expects based on the initial, partial IDENTIFY response.
(1) The old method (34GB WD Raptor drives) will spin up on receipt of
any media-access command. The trick here being, we that don't have
full IDENTIFY info to properly issue just *any* media command,
so this has to be controlled carefully.
(2) The more common method is for the drive to require an explicit
set-features "spin-up" subcommand after the IDENTIFY.
The patch below implements the latter method (tested, works for me).
I think we would want to test bit 6 of IDENTIFY DEVICE word 83, issue
SET FEATURES - SPIN UP command if set, otherwise do a READ VERIFY or
some other media access command.
But as you can see, there is an "#if 0 FIXME" section around
the code which attempts to deal with the "spin up on any media access"
variant of this protocol. That code just doesn't work for me,
and I'm hoping Jeff/Tejun might be able to point out where it's gone silly.
+#if 0
+ /*
+ * FIXME: this always fails with AC_ERR_DEV,
+ * even when issued on a spun-up drive
+ * (accomplished by commenting out the if-stmt below).
+ *
+ * What's wrong here???
+ */
+ if (!tried_spinup && id[2] == 0x8c73)
+ {
+ tried_spinup = 1;
+ /*
+ * Drive powered up in standby mode, and returned only
+ * partial IDENTIFY data. This requires a media access
+ * command (to force a spin-up) before the drive can
+ * return a complete set of IDENTIFY data.
+ * Here, we use READ_VERIFY(LBA=0) to force the spin-up.
+ */
ata_exec_internal() passes ATA_QCFLAG_RESULT_TF to the queued cmd. So,
what values are returned by the device in the taskfile registers?
AC_ERR_DEV means the command made it all the way to the device, which
then spit back the command with ERR=1 in the Status shadow register.
Jeff
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