Hi Finn,
On Sun, Jun 2, 2019 at 3:29 AM Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx> wrote:
A system bus error during a PDMA transfer can mess up the calculation of
the transfer residual (the PDMA handshaking hardware lacks a byte
counter). This results in data corruption.
The algorithm in this patch anticipates a bus error by starting each
transfer with a MOVE.B instruction. If a bus error is caught the transfer
will be retried. If a bus error is caught later in the transfer (for a
MOVE.W instruction) the transfer gets failed and subsequent requests for
that target will use PIO instead of PDMA.
This avoids the "!REQ and !ACK" error so the severity level of that
message is reduced to KERN_DEBUG.
Cc: Michael Schmitz <schmitzmic@xxxxxxxxx>
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v4.14+
Fixes: 3a0f64bfa907 ("mac_scsi: Fix pseudo DMA implementation")
Reported-by: Chris Jones <chris@xxxxxxxxxxxxxxxx>
Tested-by: Stan Johnson <userm57@xxxxxxxxx>
Signed-off-by: Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx>
Thanks for your patch!
---
arch/m68k/include/asm/mac_pdma.h | 179 +++++++++++++++++++++++++++
drivers/scsi/mac_scsi.c | 201 ++++++++-----------------------
Why have you moved the PDMA implementation to a header file under
arch/m68k/? Do you intend to reuse it by other drivers?
If not, please keep it in the driver, so (a) you don't need an ack from
me ;-), and (b) your change may be easier to review.
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
