Message-Id: <201508042006.57727@pali>
Date:	Tue, 4 Aug 2015 20:06:57 +0200
From:	Pali Rohár <pali.rohar@...il.com>
To:	Robert Hancock <hancockrwd@...il.com>
Cc:	Jeff Garzik <jeff@...zik.org>, Robert Hancock <hancockr@...w.ca>,
	Tejun Heo <tj@...nel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	"linux-kernel" <linux-kernel@...r.kernel.org>
Subject: Re: linux: sata_nv: adma support

On Monday 03 August 2015 05:02:15 Robert Hancock wrote:
> On Sun, Aug 2, 2015 at 3:08 AM, Pali Rohár <pali.rohar@...il.com>
> wrote:
> > On Sunday 02 August 2015 03:45:32 Robert Hancock wrote:
> >> On Sat, Aug 1, 2015 at 2:09 PM, Pali Rohár <pali.rohar@...il.com>
> >> 
> >> wrote:
> >> > On Thursday 25 December 2014 07:22:13 Robert Hancock wrote:
> >> >> On Tue, Dec 23, 2014 at 1:51 PM, Pali Rohár
> >> >> <pali.rohar@...il.com>
> >> >> 
> >> >> wrote:
> >> >> > 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?
> >> >> 
> >> >> > 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@...il.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?
> 
> As far as I know, yes.
> 
> >> 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).
> 
> There's no such scripts in Fedora, so either they removed it, or it's
> something that either Debian or Ubuntu has added in.
> 
> > 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?
> 
> Does the get command work without ADMA enabled?

I requested to boot that machine with turned off ADMA. I verified it is 
turned off as I found sata_nv.adma=0 in /proc/cmdline and file 
/sys/module/sata_nv/parameters/adma contains big N.

I called hdparm:

$ sudo hdparm -B254 /dev/sda

/dev/sda:
 setting Advanced Power Management level to 0xfe (254)
 HDIO_DRIVE_CMD failed: Input/output error
 APM_level      = not supported

It failed, but I do not see any error message in dmesg. There is nothing 
new in dmesg.

So looks like I'm not able to set APM... But why in ADMA mode it 
generates some error and in non ADMA mode no error? Strange!

-- 
Pali Rohár
pali.rohar@...il.com

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