Re: [PATCH 0/2] Experimental Amiga Zorro ESP driver

Tuomas Vainikka
2013-09-10T21:13:14Z

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On 08/22/2013 11:34 PM, Michael Schmitz wrote:
> Hello Tuomas,
>
>>> No idea which functions you refer to regarding PIO (reading from FIFO).
>>> Anyway, the DMA will read from the same FIFO that the CPU would, if I
>>> understand DMA correctly. There really should be no difference-
>> esp.scsi.c:1058 versus esp.scsi.c:1120
> I suppose this is because reconnect_with_tag() cannot rely on the tag
> information already being in the FIFO when it is called from
> esp_reconnect(). esp_reconnect() is called from the reselection
> interrupt so the fifo data is already present.
>
>> In:
>> http://pdf.datasheetcatalog.com/datasheet/AdvancedMicroDevices/mXxxsy.pdf
>> page 42: Enable Selection/Reselection Command (Command Code 44H/C4H)
>>
>> explains why the bytes might end up in FIFO; The chip DMA got disabled at
>> some point. Also, you need to explicitly issue a specific (don't know which,
>> yet) command to let the DMA access the FIFO.
> The chip DMA should be activated by the ESP_CMD_DMA bit that is set in
> all uses of send_dma_cmd. I can't see where the DMA would have been
> disabled.
>
>>> The DMA transfer function can be changed to fetch less than seven bytes
>>> from the FIFO by PIO instead of setting up DMA transfer (just poll the FIFO
>>> after sending the command to the ESP, instead of first setting up the DMA
>>> then sending the command),
>>>
>> I'd rather find out why and where the DMA is disabled before we resort to
>> PIO. It is also possible that the chip interrupt is cleared prematurely by
>> reading the interrupt register, in which case the interrupt is not seen by
>> The Loop.
> That's the attitude - my suggestion was purely pragmatic, in order to
> overcome that particular roadblock and see whether there's further
> issues. But fixing this properly would be much preferred.
>
> David Miller is still maintainer of the ESP code - I can't think of
> anyone better suited to answer ESP specific questions really.
>
> Cheers,
>
> Michael
>
I got it to work. Somehow, at least. I wrote the driver to use PIO for
command block reads and writes, and found out that it didn't fix the
problem. Using PIO, only the first byte of the tag message comes
through. It might not be esp_scsi's fault, but there seems to be an
assumption that all devices support TCQ. Also, no SCSI-2 features seem
to be enabled in the chip by esp_scsi.

To cut the long story short, I hardwired TCQ off with a replacement
function for esp_slave_configure().
The replacement function resides in zorro_esp.c and is essentially doing
the same thing as the original if ESP_DEFAULT_TAGS was set to zero in
esp_scsi.h.

There is no need for PIO with the above hack.

I've attached a log of the module loading and some operations on the
attached hdd. Note that there are messages such as

[ 4627.040000] sd 0:0:0:0: [sda] Got wrong page
and
[ 5106.340000] sda1: WRITE SAME failed. Manually zeroing.

which don't seem normal.

-Tuomas

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