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From: Guenter Roeck <linux@roeck-us.net>
To: Mark Brown <broonie@kernel.org>
Cc: Jean Delvare <khali@linux-fr.org>,
	LM Sensors <lm-sensors@lm-sensors.org>,
	linux-kernel@vger.kernel.org, Liam Girdwood <lgirdwood@gmail.com>,
	Wei Ni <wni@nvidia.com>
Subject: Re: [lm-sensors] lm90 driver no longer working on PCs in 3.13
Date: Sun, 26 Jan 2014 21:47:09 +0000	[thread overview]
Message-ID: <52E5825D.9090104@roeck-us.net> (raw)
In-Reply-To: <20140126205216.GJ11727@sirena.org.uk>

On 01/26/2014 12:52 PM, Mark Brown wrote:
> On Sun, Jan 26, 2014 at 12:44:38PM -0800, Guenter Roeck wrote:
>> On 01/26/2014 12:13 PM, Jean Delvare wrote:
>
>>> Me, I really don't know. I seem to remember I tested Wei's patch set on
>>> an emulated ADM1032 chip and it was working fine. So maybe it depends
>>> on the kernel configuration, or something changed on the regulator side
>>> meanwhile.
>
>> The regulator code changed with 3.13; the dummy regulator no longer exists,
>> and the functionality it provided is supposed to be handled automatically.
>> But that only really works on devicetree based systems and otherwise returns
>> -EPROBE_DEFER as mentioned above.
>
> CONFIG_REGULATOR_DUMMY should never have been used in production, it was
> a debug tool to help bringup but it broke things as often as it fixed
> them particularly with init ordering which is why it generated a warning
> when it was used.
>
> The dummy driver is still there, if you're doing bringup you can hack it
> in still or if you genuniely used it then specify that full constraints
> are provided like the changelog says (and as I've previously said).
>
>> Another possible fix would be to have the regulator core return -ENODEV
>> instead of -EPROBE_DEFER on non-dt systems. No idea if this would be acceptable
>> or even feasible.
>
> No, this would introduce breakage due to init ordering.
>

You have a solution for that in dt configurations. I don't think you have one for
non-dt systems - you simply assume that all regulators are there. For dt, you even
have a constraint to tell the kernel if regulator configurations are fully specified,
and you automatically return success if not and if a regulator does not exist.
So you know that there is a problem. For non-DT configurations you simply assume and
expect that regulators are all declared. I don't think that is a feasible approach
for non-DT systems.

Guenter


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WARNING: multiple messages have this Message-ID (diff)
From: Guenter Roeck <linux@roeck-us.net>
To: Mark Brown <broonie@kernel.org>
Cc: Jean Delvare <khali@linux-fr.org>,
	LM Sensors <lm-sensors@lm-sensors.org>,
	linux-kernel@vger.kernel.org, Liam Girdwood <lgirdwood@gmail.com>,
	Wei Ni <wni@nvidia.com>
Subject: Re: lm90 driver no longer working on PCs in 3.13
Date: Sun, 26 Jan 2014 13:47:09 -0800	[thread overview]
Message-ID: <52E5825D.9090104@roeck-us.net> (raw)
In-Reply-To: <20140126205216.GJ11727@sirena.org.uk>

On 01/26/2014 12:52 PM, Mark Brown wrote:
> On Sun, Jan 26, 2014 at 12:44:38PM -0800, Guenter Roeck wrote:
>> On 01/26/2014 12:13 PM, Jean Delvare wrote:
>
>>> Me, I really don't know. I seem to remember I tested Wei's patch set on
>>> an emulated ADM1032 chip and it was working fine. So maybe it depends
>>> on the kernel configuration, or something changed on the regulator side
>>> meanwhile.
>
>> The regulator code changed with 3.13; the dummy regulator no longer exists,
>> and the functionality it provided is supposed to be handled automatically.
>> But that only really works on devicetree based systems and otherwise returns
>> -EPROBE_DEFER as mentioned above.
>
> CONFIG_REGULATOR_DUMMY should never have been used in production, it was
> a debug tool to help bringup but it broke things as often as it fixed
> them particularly with init ordering which is why it generated a warning
> when it was used.
>
> The dummy driver is still there, if you're doing bringup you can hack it
> in still or if you genuniely used it then specify that full constraints
> are provided like the changelog says (and as I've previously said).
>
>> Another possible fix would be to have the regulator core return -ENODEV
>> instead of -EPROBE_DEFER on non-dt systems. No idea if this would be acceptable
>> or even feasible.
>
> No, this would introduce breakage due to init ordering.
>

You have a solution for that in dt configurations. I don't think you have one for
non-dt systems - you simply assume that all regulators are there. For dt, you even
have a constraint to tell the kernel if regulator configurations are fully specified,
and you automatically return success if not and if a regulator does not exist.
So you know that there is a problem. For non-DT configurations you simply assume and
expect that regulators are all declared. I don't think that is a feasible approach
for non-DT systems.

Guenter


  reply	other threads:[~2014-01-26 21:47 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-26 19:28 [lm-sensors] lm90 driver no longer working on PCs in 3.13 Guenter Roeck
2014-01-26 19:28 ` Guenter Roeck
2014-01-26 20:13 ` [lm-sensors] " Jean Delvare
2014-01-26 20:13   ` Jean Delvare
2014-01-26 20:42   ` [lm-sensors] " Mark Brown
2014-01-26 20:42     ` Mark Brown
2014-01-26 20:44   ` [lm-sensors] " Guenter Roeck
2014-01-26 20:44     ` Guenter Roeck
2014-01-26 20:49     ` [lm-sensors] " Jean Delvare
2014-01-26 20:49       ` Jean Delvare
2014-01-26 21:22       ` [lm-sensors] " Mark Brown
2014-01-26 21:22         ` Mark Brown
2014-01-26 21:40         ` [lm-sensors] " Guenter Roeck
2014-01-26 21:40           ` Guenter Roeck
2014-01-26 21:53           ` [lm-sensors] " Mark Brown
2014-01-26 21:53             ` Mark Brown
2014-01-26 22:02             ` [lm-sensors] " Guenter Roeck
2014-01-26 22:02               ` Guenter Roeck
2014-01-26 23:37               ` [lm-sensors] " Mark Brown
2014-01-26 23:37                 ` Mark Brown
2014-01-26 21:44         ` [lm-sensors] " Jean Delvare
2014-01-26 21:44           ` Jean Delvare
2014-01-26 23:15           ` [lm-sensors] " Mark Brown
2014-01-26 23:15             ` Mark Brown
2014-01-27 10:10             ` [lm-sensors] " Geert Uytterhoeven
2014-01-27 10:10               ` Geert Uytterhoeven
2014-01-27 13:18               ` [lm-sensors] " Mark Brown
2014-01-27 13:18                 ` Mark Brown
2014-01-26 21:50       ` [lm-sensors] " Guenter Roeck
2014-01-26 21:50         ` Guenter Roeck
2014-01-26 22:04         ` [lm-sensors] " Guenter Roeck
2014-01-26 22:04           ` Guenter Roeck
2014-01-26 23:51           ` Mark Brown
2014-01-26 23:51             ` Mark Brown
2014-01-27  4:16             ` Guenter Roeck
2014-01-27  4:16               ` Guenter Roeck
2014-01-27 10:34               ` Mark Brown
2014-01-27 10:34                 ` Mark Brown
2014-01-27 17:19             ` Stephen Warren
2014-01-27 17:19               ` Stephen Warren
2014-01-27 18:50               ` Guenter Roeck
2014-01-27 18:50                 ` Guenter Roeck
2014-01-27 22:04                 ` Jean Delvare
2014-01-27 22:04                   ` Jean Delvare
2014-01-27 23:41                   ` Guenter Roeck
2014-01-27 23:41                     ` Guenter Roeck
2014-01-27 23:58                     ` Mark Brown
2014-01-27 23:58                       ` Mark Brown
2014-01-28  2:33                       ` Guenter Roeck
2014-01-28  2:33                         ` Guenter Roeck
2014-01-28 10:24                         ` Mark Brown
2014-01-28 10:24                           ` Mark Brown
2014-01-28 12:34                   ` Mark Brown
2014-01-28 12:34                     ` Mark Brown
2014-01-27 22:36                 ` Mark Brown
2014-01-27 22:36                   ` Mark Brown
2014-01-26 20:52     ` Mark Brown
2014-01-26 20:52       ` Mark Brown
2014-01-26 21:47       ` Guenter Roeck [this message]
2014-01-26 21:47         ` Guenter Roeck
2014-01-26 22:01         ` [lm-sensors] " Mark Brown
2014-01-26 22:01           ` Mark Brown

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