Re: [PATCH 1/2] pinctrl: sunxi: Deal with per-bank regulators

[Chen-Yu Tsai <wens@xxxxxxxx>]

On Thu, Dec 6, 2018 at 10:02 PM Maxime Ripard <maxime.ripard@xxxxxxxxxxx> wrote:
>
> The Allwinner SoCs have on most of their GPIO banks a regulator input.
>
> This issue was mainly ignored so far because either the regulator was a
> static regulator that would be providing power anyway, or the bank was used
> for a feature unsupported so far (CSI). For the odd cases, enabling it in
> the bootloader was the preferred option.
>
> However, now that we are starting to support those features, and that we
> can't really rely on the bootloader for this, we need to model those
> regulators as such in the DT.
>
> This is slightly more complicated than what it looks like, since some
> regulators will be tied to the PMIC, and in order to have access to the
> PMIC bus, you need to mux its pins, which will need the pinctrl driver,
> that needs the regulator driver to be registered. And this is how you get a
> circular dependency.
>
> In practice however, the hardware cannot fall into this case since it would
> result in a completely unusable bus. In order to avoid that circular
> dependency, we can thus get and enable the regulators at pin_request time.
> We'll then need to account for the references of all the pins of a
> particular branch to know when to put the reference, but it works pretty
> nicely once implemented.
>
> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxx>

I'm getting a warning on my Bananapi M1+:

[  +0.004918] sun4i-pinctrl 1c20800.pinctrl: 1c20800.pinctrl supply
vcc-pa not found, using dummy regulator
[  +0.009931] sun7i-dwmac 1c50000.ethernet: PTP uses main clock
[  +0.005764] sun7i-dwmac 1c50000.ethernet: no reset control found
[  +0.006111] ------------[ cut here ]------------
[  +0.004640] WARNING: CPU: 1 PID: 1 at drivers/regulator/core.c:2054
_regulator_put.part.8+0xf8/0xfc
[  +0.009065] Modules linked in:
[  +0.003085] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.0.0-rc1 #5
[  +0.006179] Hardware name: Allwinner sun7i (A20) Family
[  +0.005252] [<c010eaf0>] (unwind_backtrace) from [<c010b854>]
(show_stack+0x10/0x14)
[  +0.007755] [<c010b854>] (show_stack) from [<c089ac28>] (dump_stack+0x88/0x9c)
[  +0.007233] [<c089ac28>] (dump_stack) from [<c0127450>] (__warn+0xd4/0xf0)
[  +0.006881] [<c0127450>] (__warn) from [<c01274ac>]
(warn_slowpath_null+0x40/0x48)
[  +0.007576] [<c01274ac>] (warn_slowpath_null) from [<c03fd25c>]
(_regulator_put.part.8+0xf8/0xfc)
[  +0.008876] [<c03fd25c>] (_regulator_put.part.8) from [<c03fd288>]
(regulator_put+0x28/0x38)
[  +0.008446] [<c03fd288>] (regulator_put) from [<c03c5f2c>]
(sunxi_pmx_free+0x38/0x48)
[  +0.007837] [<c03c5f2c>] (sunxi_pmx_free) from [<c03c2444>]
(pin_free+0x9c/0xfc)
[  +0.007402] [<c03c2444>] (pin_free) from [<c03c2fb0>]
(pinmux_disable_setting+0x118/0x184)
[  +0.008271] [<c03c2fb0>] (pinmux_disable_setting) from [<c03c0060>]
(pinctrl_free+0x13c/0x144)
[  +0.008619] [<c03c0060>] (pinctrl_free) from [<c048c6a0>]
(release_nodes+0x1bc/0x200)
[  +0.007839] [<c048c6a0>] (release_nodes) from [<c0488964>]
(really_probe+0x110/0x2cc)
[  +0.007838] [<c0488964>] (really_probe) from [<c0488c84>]
(driver_probe_device+0x60/0x16c)
[  +0.008270] [<c0488c84>] (driver_probe_device) from [<c0488e6c>]
(__driver_attach+0xdc/0xe0)
[  +0.008444] [<c0488e6c>] (__driver_attach) from [<c0486d44>]
(bus_for_each_dev+0x74/0xb4)
[  +0.008184] [<c0486d44>] (bus_for_each_dev) from [<c0487edc>]
(bus_add_driver+0x1bc/0x200)
[  +0.008270] [<c0487edc>] (bus_add_driver) from [<c04897ac>]
(driver_register+0x74/0x108)
[  +0.008098] [<c04897ac>] (driver_register) from [<c010270c>]
(do_one_initcall+0x7c/0x1a8)
[  +0.008187] [<c010270c>] (do_one_initcall) from [<c0d00e14>]
(kernel_init_freeable+0x13c/0x1d8)
[  +0.008705] [<c0d00e14>] (kernel_init_freeable) from [<c08b08b8>]
(kernel_init+0x8/0x110)
[  +0.008184] [<c08b08b8>] (kernel_init) from [<c01010e8>]
(ret_from_fork+0x14/0x2c)
[  +0.007570] Exception stack(0xef04ffb0 to 0xef04fff8)
[  +0.005054] ffa0:                                     00000000
00000000 00000000 00000000
[  +0.008180] ffc0: 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000
[  +0.008179] ffe0: 00000000 00000000 00000000 00000000 00000013 00000000
[  +0.006654] ---[ end trace 2bdb4a597b3c54ef ]---

Note that sun7i-dwmac probe is deferred here. The instance where the
probe succeeds shows
no warning.

ChenYu