On Sunday 02 August 2015 03:45:32 Robert Hancock wrote:

On Sat, Aug 1, 2015 at 2:09 PM, Pali Rohár [off-list ref]
wrote:

quoted

On Thursday 25 December 2014 07:22:13 Robert Hancock wrote:

quoted

On Tue, Dec 23, 2014 at 1:51 PM, Pali Rohár [off-list ref]

wrote:

quoted

Hello,

I have nvidia nforce4 motherboard with nvidia sata controller:

00:07.0 IDE interface [0101]: NVIDIA Corporation CK804 Serial
ATA Controller [10de:0054] (rev f3)
00:08.0 IDE interface [0101]: NVIDIA Corporation CK804 Serial
ATA Controller [10de:0055] (rev f3)

I manually enabled adma mode (which is disabled by default) by
adding sata_nv.adma=1 to grub cmdline. In git history I found
that enabling adma mode includes NCQ support and reduced CPU
overhead. It looks like adma mode is working, but at every boot
I see one same error message in dmesg:

[   16.823514] ata1.00: exception Emask 0x1 SAct 0x0 SErr 0x0
action 0x0
[   16.823520] ata1.00: CPB resp_flags 0x11: , CMD error
[   16.823524] ata1.00: failed command: SET FEATURES
[   16.823530] ata1.00: cmd ef/05:fe:00:00:00/00:00:00:00:00/40
tag 16
[   16.823530]          res 51/04:fe:00:00:00/00:00:00:00:00/40
Emask 0x1 (device error)
[   16.823533] ata1.00: status: { DRDY ERR }
[   16.823535] ata1.00: error: { ABRT }

When adma is disabled then this error message is not generated.

It looks like something is trying to issue a command to disable
APM power management on the drive, and the command fails (likely
because it doesn't support that command). I'm not sure where that
would be coming from - I'm pretty sure the kernel doesn't issue
that command itself. Something that's part of your distro
perhaps?

I don't know why it would only be failing in ADMA mode either,
though depending on where the command is coming from, maybe it's
not being issued otherwise for some reason?

quoted

What does that error message means? It is critical? What is that
command SET FEATURES doing? Are there any problems with adma
mode on nforce4 motherboards? Because I did not see any
problems (except that one error message).

--
Pali Rohár
pali.rohar@gmail.com

Hello,

now after long time I did more investigation and that error is
reported for every connected HDD. I identified that it comes from
udev script

 /lib/udev/rules.d/85-hdparm.rules

which just call script /lib/udev/hdparm for every one connected
HDD.

Script /lib/udev/hdparm just call:
 /sbin/hdparm -B254 $DRIVE

And that -B254 cause above error message in dmesg log. Output from

hdparm is:
 /dev/sda:
  setting Advanced Power Management level to 0xfe (254)
  APM_level      = not supported

Any idea why in ADMA mode it cause above error (APM unsupported)
and in non ADMA mode it is working fine? Maybe APM ATA commands
should not be sent via ADMA?

Here is another output:
 $ sudo hdparm -I /dev/sda | grep -i power
 
            *    Power Management feature set
            
                 Power-Up In Standby feature set
            
            *    SET_FEATURES required to spinup after power up
            *    Host-initiated interface power management

The "set features" command is a non-data command so based on our
current knowledge, it should work in ADMA mode. However, these NVIDIA
SATAs are black boxes, and rather buggy ones at that, so it's
possible there's an unknown issue there.

Maybe I should note that hdparm -I did not generated any error message. 
I post is here because it show "Power Management feature set" is 
supported by HDD. This indicate that HDD supports -B (APM) command, 
right?

The easiest way to test that would be to take out the condition check
for qc->tf.protocol == ATA_PROT_NODATA in nv_adma_use_reg_mode in
drivers/ata/sata_nv.c. That would force it to disable ADMA for all
non-data commands.

Ok, as now I have just SSH access to that machine, I will do kernel 
patching later (when I have physical access to it).

I really don't know why Ubuntu is disabling APM on all drives on
bootup however. Especially for laptops, that seems like a silly thing
to do explicitly. Sounds like one of the silly things Ubuntu is known
to do without consulting people.

Looks like this comes from upstream udev/systemd project :-( Anyway, for 
laptops on battery ubuntu has another set of scripts which turn on APM 
(based on connected/disconnected AC adapter).

That udev script which turn off APM is called when any disk is attached 
to system (so at boot time it is called for every one disk).

Now I just masked that udev script and it is no longer called...

Anyway if I call hdparm -B /dev/sda I get output:

APM_level      = not supported

And important is that there is no error message in dmesg. I get it only 
if I call hdparm -B with parameter (set option). But APM should be 
supported, right?

-- 
Pali Rohár
pali.rohar@gmail.com