svn commit: r298274 - head/sys/dev/spibus

[Patrick Kelsey]

On Tue, Apr 19, 2016 at 4:21 PM, Ian Lepore <ian at freebsd.org> wrote:

> On Tue, 2016-04-19 at 13:17 -0700, Juli Mallett wrote:
> > Patrick Kelsey offered an mmcspi driver for FreeBSD, but nobody
> > seemed
> > interested.  I know of one proprietary branch of FreeBSD using it.
> > You might poke him if you want to know how he dealt with this, and if
> > you want to commit his driver.
> >
>
> Patrick is a committer, maybe he should just commit it. :)
>

What I believe originally held up that driver being committed (by others -
this was before my commit bit) was that I relied on some out-of-tree spibus
changes Luiz had made (as I recall, mainly being able to reserve the SPI
bus for multiple transactions), and getting those into the tree would have
required updating/testing other existing SPI drivers, based on feedback I
received at the time.  All I had was the RB450G that I developed and tested
the driver with, so I really couldn't address that issue, and then work
took me in some other direction entirely.  Some or all of these spibus
changes that I relied on might now be in the tree, I'm not sure offhand.  I
am sure though that a huge stack of other things I need to get through has
chronically kept me from updating that driver to current and retesting.

When I wrote that driver, I put a lot of effort into testing it against as
many different cards as I could obtain at the time - I believe 30 or so in
total, all the details are in the code that was posted to the list back
then.  I encountered a number of strange/unexpected behaviors in that set
of cards, and all of that hard-won knowledge is in that driver, including a
much less complex fix for a shifted-response-data issue than you will see
if you look at the Linux mmcpsi driver (as I recall, the Linux driver has
code to arbitrarily bit-shift card response data, and to detect when that
should be done, but it turns out that can be avoided entirely by inserting
idle cycles in the right place when sending the command).

-Patrick