Re: Modified Linux 4.1.20 (mac+scsi) on Quadra 660av

[Michael Schmitz <schmitzmic@gmail.com>]

Hi Finn,

the problem with trying to read two tag bytes does sound familiar - I
believe we ran into that one (or a similar one) while trying to revive
the Amiga ESP drivers.

Tuomas used scsi_deactivate_tcq() in a driver specific
esp_slave_configure() hook but that interface later disappeared. In the
last version I tested, I added the following code after domain
validation in the driver specific esp_slave_configure()

+       /*
+        * Hardwire TQC capability of target _off_ after
+        * domain validation (which might have probed and
+        * negotiated TQC available)
+        */
+       dev->tagged_supported = 0;
+       dev->simple_tags = 0;
+

I tried all sorts of things with the chip config registers, to no avail.
Your report that this only happens with some disks exonerates the driver ...

HTH,

	Michael


Am 03.08.2016 um 16:16 schrieb Finn Thain:
> 
> On Tue, 2 Aug 2016, Mac User wrote:
> 
>>> Please send pictures. You can use the kernel parameter 
>>> "fbcon=font:ProFont6x11" to get more text on the screen if it scrolls 
>>> too fast.
>>>
>>
>> Please see attached.  Thanks..
>> [...]
>> scsi host0: esp
>> scsi 0:0:0:0: Direct-Access SEAGATE ST318417N 0105 PQ: 0 ANSI: 3
>> scsi target0:0:0: Beginning Domain Validation
>> scsi host0: Reconnect IRQ2 timeout
> 
> A bit of Googling tells me that I've been here before (I had forgotten):
> 
> commit 02507a80b35edd720480540d917e9f92cc371009
> Author: Finn Thain <fthain@telegraphics.com.au>
> Date:   Sat Dec 5 12:30:42 2009 +1100
> 
>     [SCSI] mac_esp: fix PIO mode, take 2
>     
>     The mac_esp PIO algorithm no longer works in 2.6.31 and crashes my Centris
>     660av. So here's a better one.
>     
>     Also, force async with esp_set_offset() rather than esp_slave_configure().
>     
>     One of the SCSI drives I tested still doesn't like the PIO mode and fails
>     with "esp: esp0: Reconnect IRQ2 timeout" (the same drive works fine in
>     PDMA mode).
>     
>     This failure happens when esp_reconnect_with_tag() tries to read in two
>     tag bytes but the chip only provides one (0x20). I don't know what causes
>     this. I decided not to waste any more time trying to fix it because the
>     best solution is to rip out the PIO mode altogether and use the DMA
>     engine.
>     
> 
> So it appears that this bug is not a regression. I guess you have 3 
> options: find a compatible drive, implement DMA with the PSC chip, or 
> debug the esp_reconnect_with_tag() implementation for PIO use.
> 
> Apple never provided public documentation for the PSC chip, which is why 
> there's no DMA support for SCSI on AV Quadras, and also why we have code 
> like this in macmace.c:
> 
>         /* Not sure what this does */
> 
>         while ((baka = psc_read_long(PSC_MYSTERY)) != psc_read_long(PSC_MYSTERY));
>         if (!(baka & 0x60000000)) return IRQ_NONE;
> 
> You could tackle the esp_reconnect_with_tag() bug by increasing the 
> ESP_RESELECT_TAG_LIMIT timeout and setting some kernel parameters:
>   scsi_mod.scan=sync  esp_scsi.esp_debug=0x241
> 
> In my experience, the only practical way to debug mac scsi drivers is to 
> make the driver modular, boot over ethernet and then use insmod and rmmod 
> to test changes to the module.
>