[Bug 252735] Acer Aspire: mmc disk unusable on CURRENT (patch)

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252735

            Bug ID: 252735
           Summary: Acer Aspire: mmc disk unusable on CURRENT (patch)
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs at FreeBSD.org
          Reporter: ashafer at badland.io

(I'm filing this bug to track a review I submitted in May 2020 that still
hasn't gotten attention. Filing a bug to prevent the review from getting lost
in space)

Problem:
I bought a cheap acer aspire (A114-32-P7E5) to hack freebsd on. The disk it
comes with is some sort of low quality eMMC that freebsd doesn't like out of
the box. I could boot from a usb drive, but couldn't use the mmc disk. I'm
guessing that other cheap laptops have the same problem. The review I link
fixes the problem.

Solution:

Patch at: https://reviews.freebsd.org/D24740
I've been running this (daily use) for ~9months with no problems.

>From reading around online, it seems that some number of cards can not depend
on
CMD13 to check for errors while switching to HS200. They generate BADCRC errors
for a short bit before CMD13 succeeds. It's my understanding that CMD13 is used
after
CMD6 to verify switching has completed, and if these BADCRC errors are observed
we should ignore them and retry CMD13.

I've update mmc_switch_status to have an argument to ignore bad crc errors,
which the caller sets if we are switching to HS200. This seemed to be the best
place to do this.

Suspend/resume still doesn't work, but please let me know if there's anything I
can do to improve/commit this. I'd love to see this committed so that I can
stop having to track CURRENT on this laptop. Thanks!

-- 
You are receiving this mail because:
You are the assignee for the bug.