Re: [PATCH] ahci: force 32-bit DMA for JMicron JMB582/JMB585

[Mario Limonciello <mario.limonciello@amd.com>]

< snip >

> So: tell me which test would actually be useful and I will run it and
> report the result either way, including a negative one. I would rather
> spend the window on the question you want answered than guess at it.
> 
> Alvin Lim

Two things:

1. lspci -ttvvnn
2. Turn on  amd_smn_debugfs_enable=1 on kernel command line.
Then use debugfs to get me the outputs from the SMN reads of these 
registers:


        0x111401d0,
        0x111411d0,
        0x111421d0,
        0x111431d0,
        0x111441d0,
        0x112401d0,
        0x112411d0,
        0x112421d0,
        0x112431d0,
        0x112441d0,
        0x112451d0,
        0x113401d0,
        0x114401d0,

Something like this might work.

sudo bash <<'EOF'
set -euo pipefail

if ! mountpoint -q /sys/kernel/debug; then
     mount -t debugfs debugfs /sys/kernel/debug
fi

dir=/sys/kernel/debug/x86/amd_smn
test -d "$dir" || {
     echo "Missing $dir; verify CONFIG_DEBUG_FS and 
amd_smn_debugfs_enable=1"
     exit 1
}

addresses=(
     0x111401d0
     0x111411d0
     0x111421d0
     0x111431d0
     0x111441d0
     0x112401d0
     0x112411d0
     0x112421d0
     0x112431d0
     0x112441d0
     0x112451d0
     0x113401d0
     0x114401d0
)

printf '0\n' > "$dir/node"

for address in "${addresses[@]}"; do
     printf '%s\n' "$address" > "$dir/address"

     old=$(cat "$dir/value")
     [[ $old =~ ^0x[[:xdigit:]]{8}$ ]] || {
         echo "$address: invalid read: $old"
         exit 1
     }

     printf '%s: %s\n' "$address" "$old"
done
EOF