Re: Shark LED and I2C drivers

[Jason Thorpe <thorpej%me.com@localhost>]

> On Apr 28, 2021, at 11:15 PM, Julian Coleman <jdc%coris.org.uk@localhost> wrote:
> 
> Hi,
> 
>> I'm going to merge this into my thorpej-i2c-spi-conf branch.  I am trying to reduce the proliferation of "add more child devices in dictionaries", so I'd prefer they don't land in the trunk in current form.
> 
> I've updated the patch for the config changes:
> 
>  http://ftp.netbsd.org/pub/NetBSD/misc/jdc/shark/shark-iic-led.diff

I have a slightly different version of this change merged into my local tree… I’ve created a separate “sequoia” device_t node that attaches at the “isa” OFW package, and then connect the Shark-specific (and very Sequoia-dependent) “sharkiic” as a child of “sequoia”.  “ofisa” is then also attached as a child of “sequoia”.

> Looking a bit further in the Shark OFW, there is an SPI EEPROM, driven via
> bitbanging the gpio pins [1].  The pin configuration is available from the
> Forth words too, so it should be possible to use it via a bit-banging SPI
> mode 0 driver.  However, this is already in the OFW tee, so doesn't need
> us to add additional devices.
> 
>>> Seeprom attaches because the DIMM's are not SPD-compatible.  I was however,
>>> able to inspect their contents using:
>>> 
>>> for i in 0 1; do dd if=/dev/seeprom$i bs=256k count=1 | hexdump -C; done
>>> 
>>> and see that it has 2 Samsung KMM366S203BTN-G2 (16MB PC-66) DIMM's installed.
>> 
>> Where is the documentation for the eeprom data format?\
> 
> In this case, the DIMM's are almost following the SPD specification [2], but
> the checksum field is 0.  We verify the checksum in the spdmem driver for
> older memory types [3] so fail to attach here.  I did wonder if we should
> also handle the zero checksum with a warning, but it seems a rare case.  It
> would allow us to just have the spdmem driver though, so save some memory.
> Maybe having seeprom commented out in GENERIC is a reasonable compromise?

Seems like we could handle the “looks like SPD, but has a zero checksum” in a pretty reasonable fashion in “spdmem"

-- thorpej