Date: Fri, 10 Mar 2017 10:10:30 -0800
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
To: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: Andrew Duggan <aduggan@synaptics.com>, linux-kernel@vger.kernel.org,
        linux-input@vger.kernel.org
Subject: Re: [PATCH 0/8] PS
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On Fri, Mar 10, 2017 at 07:04:22PM +0100, Benjamin Tissoires wrote:
> On Mar 10 2017 or thereabouts, Dmitry Torokhov wrote:
> > On Fri, Mar 10, 2017 at 04:57:35PM +0100, Benjamin Tissoires wrote:
> > > Hi Dmitry,
> > > 
> > > On Mar 09 2017 or thereabouts, Dmitry Torokhov wrote:
> > > > Hi,
> > > > 
> > > > This is refresh of Benjamin's patches trying to bridge PS/2 and SMbus
> > > > devices for better support of Synaptics RMI4 touchpads (and Elans later).
> > > 
> > > Thanks!
> > > 
> > > I have some issues/comments and am still working on those. Here are some
> > > general comments:
> > > 
> > > > 
> > > > The main difference is that we do not have platform device, as it only
> > > > adds another indirection level, and have psmouse create SMBus companion
> > > 
> > > The purpose of having the platform device was to not have dependency
> > > between psmouse and I2C. Right now I think that patch 6/8 will fail to
> > > compile if I2C=m and PSMOUSE=y (I may be wrong).
> > 
> > This is taken care by the following guards in users if MOUSE_PS2_SMBUS:
> > 
> > depends on I2C=y || I2C=MOUSE_PS2
> 
> I can see this guards for MOUSE_PS2_SYNAPTICS_SMBUS, but not for
> MOUSE_PS2_SMBUS. So unless I am completely missing the point, if users
> disable SYNAPTICS_SMBUS but keep PS2_SMBUS there might be a problem.

Hmm, I'll need to play with this. MOUSE_PS2_SMBUS is not user visible.
Might end up adding condition there as well, or doing somethign more
elaborate, like Arnd did for RMI_F03_SERIO.

> 
> > 
> > I am perfectly fine to tie psmouse to I2C *core*, we do not need to have
> > adapters loaded for it to work (hopefully).
> 
> K.
> 
> > 
> > > 
> > > > directly. Because serio ports complete registration asynchronously, we do
> > > > not deadlock on psmouse_mutex when even if we have a pass-through port.
> > > > (Frankly we need to revisit this whole serio and psmouse thing, use of
> > > > global serio_mutex and psmouse_mutex is hurting us; they were needed when
> > > > driver core could not recursively iterate over device and driver lists).
> > > 
> > > Agree, this is a giant PITA.
> > > 
> > > > 
> > > > We also do not allow overriding serio driver, instead we teach psmouse
> > > > about "special" devices and let it continue own the serio port and make
> > > > sure nobody else touches it.
> > > > 
> > > > To work around issue with psmouse_reconnect() running sometimes too late,
> > > > we add "fast reconnect" option to serio. Not too pretty, but gets the job
> > > > done. We may need to revisit whole serio PM story later and stop "cheating"
> > > > and pretending that device is resumed when it is not, but for that we need
> > > > to teach PM core about devices that are OK not to wait for before resuming
> > > > userspace. Anyway, much bigger topic for later.
> > > 
> > > I thought there was already the ability to say that a driver needs to be
> > > run in a different thread for PM functions (IIRC i2c-hid uses
> > > device_enable_async_suspend(&client->dev); and this "should" do the
> > > trick).
> > 
> > The issue is that currently asynchronous resume still has to complete
> > before we start resuming userspace, as PS/2 is way too slow. So the
> > current solution marks device as resumed right away, and mouse may
> > become responsive 2 seconds later, but that is good as we do not idly
> > sit and wait but have userspace start turning on the screen and do other
> > useful stuff. Maybe user can already start typing their password into
> > screen locker.
> 
> Oh, I see. I haven't thought at the userspace issue.
> 
> > 
> > We would need to give a way to drivers to indicate to PM core just how
> > asynchronous our resume can be.
> > 
> > > 
> > > > 
> > > > This seems to be working on X1 Carbon and also not breaking my HP 1040 with
> > > > forcepad (unfortunately it seems to be using some other SMBus controller
> > > > for connecting Synaptics, as I see nothing at 0x2c when loading i2c-i801).
> > > 
> > > Well, on my T450, the SMBus connection is dead too. I can't seem to talk
> > > to the device at all. This happens when the firmware believes it needs
> > > to stay on PS/2 and gets completely deaf to I2C. I solved this by
> > > calling psmouse_deactivate(), but this time, it looks like some other
> > > function needs to be called.
> > > 
> > > I'll keep investigating and report back.
> > 
> > I've heard a rumors that HP 1020 uses a Microtech SMbus controller for
> > its touchpad, it could be that 1040 is similar.
> 
> Oh, yes, I do remember this. However, I think the device was i2c_hid,
> not SMBus. You can check if that's the case by looking at the DSDT, if
> it has a HID over I2C touchpad, then that the same issue.
> 
> > 
> > When your SMBus connection is dead do you see anything on the bus? At
> > that address? Or it is completely unresponsive?
> 
> Completely unresponsive, nothing on the bus (as if there was nothing
> physically wired).
> 
> I managed to discover that using psmouse as a module, not in bzImage
> allows to have the bus properly set. So I guess there is some timing
> issue (and that's going to be a pain to figure out).
> 
> In addition to the pdata fix I just sent in reply to 6/8, I have one
> extra fix for rmi30 in case the pdata gets corrupted (or if f30 has
> been deliberately disabled).

OK, cool.

Thanks.

-- 
Dmitry