Re: [PATCH] libata error handling fixes (ATAPI)

[Jeff Garzik <jgarzik@pobox.com>]

Tejun Heo wrote:
> * prb->fis doesn't contain proper signature after phy reset.  I just 

This makes sense.  Each PRB slot in the card's RAM only contains 
something useful after you have submitted a PRB, and had some results 
returned.


> * As all commands hang after failed TUR, which BTW fails rightfully with 
> 06h (UNIT ATTENTION due to prior reset) and then 02h's (NOT READY), I 
> avoided TUR failures by issuing REQUEST SENSE first, which returns NO 
> SENSE but does clear UA condition, and then waiting for more than 10secs 
> to give the drive time to become ready.

10 seconds is certainly a long time.

grep for msleep(150) in libata code, though.


> * With above two changes, no command fails and I can mount the cdrom.
>
> ------------------
>
> And here are things that I've found out so far....
>
> * ATAPI commands without data (TEST_UNIT_READY, ALLOW_MEDIUM_REMOVAL...) 
> work happily with any prb->ctrl flag (no flag, PRB_CTRL_PACKET_READ or 
> PRB_CTRL_PACKET_WRITE).

I suppose no-flag is the right answer, then...


> * Currently, sil24_reset_controller() is called on every error interrupt 
> to make sure the controller is ready for further operation. 
> Unfortunately, the current reset_controller() seems to reset PHY too. 
> The drive becomes NOT READY after reset_controller().  So, when TUR 
> fails, it falls into TUR, fail with NOT READY, reset which makes the 
> drive NOT READY again cycle.

Standard init sequence includes checking SStatus, then if a device is 
present, waiting until Port Ready (bit 31) of PORT_CTRL_STAT is set.  It 
doesn't look like sata_sil24 does that.


> * Wihtout sil24_reset_controller(), no further command can be issued. 
> The controller doesn't seem to be operating normally after DEV_ERR.

The port stops, when any error occurs.  For device errors, set 
PORT_CS_INIT bit in PORT_CTRL_STAT, then wait for Port Ready (bit 31, 
see above).


> So, what we need to know to make sil24 work happily with ATAPI devices.
>
> * How to get device signature on initialization.

AFAICS, you _must_ send a soft reset PRB.  This will be needed anyway, 
for port multiplier support.


> * How to make the controller operational again after a DEV_ERR without 
> affecting the attached device.

Assert PORT_CS_INIT, then wait for Port Ready.  __ONLY__ do this for 
errors PORT_CERR_DEV and PORT_CERR_SDB.

	Jeff


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