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| -rw-r--r-- | Documentation/SubmittingDrivers | 15 | ||||
| -rw-r--r-- | Documentation/power/basic-pm-debugging.txt | 106 | ||||
| -rw-r--r-- | Documentation/power/drivers-testing.txt | 42 |
3 files changed, 163 insertions, 0 deletions
diff --git a/Documentation/SubmittingDrivers b/Documentation/SubmittingDrivers index 58bead05eabb..d7e26427e426 100644 --- a/Documentation/SubmittingDrivers +++ b/Documentation/SubmittingDrivers @@ -87,6 +87,21 @@ Clarity: It helps if anyone can see how to fix the driver. It helps driver that intentionally obfuscates how the hardware works it will go in the bitbucket. +PM support: Since Linux is used on many portable and desktop systems, your + driver is likely to be used on such a system and therefore it + should support basic power management by implementing, if + necessary, the .suspend and .resume methods used during the + system-wide suspend and resume transitions. You should verify + that your driver correctly handles the suspend and resume, but + if you are unable to ensure that, please at least define the + .suspend method returning the -ENOSYS ("Function not + implemented") error. You should also try to make sure that your + driver uses as little power as possible when it's not doing + anything. For the driver testing instructions see + Documentation/power/drivers-testing.txt and for a relatively + complete overview of the power management issues related to + drivers see Documentation/power/devices.txt . + Control: In general if there is active maintainance of a driver by the author then patches will be redirected to them unless they are totally obvious and without need of checking. diff --git a/Documentation/power/basic-pm-debugging.txt b/Documentation/power/basic-pm-debugging.txt new file mode 100644 index 000000000000..1a85e2b964dc --- /dev/null +++ b/Documentation/power/basic-pm-debugging.txt @@ -0,0 +1,106 @@ +Debugging suspend and resume + (C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL + +1. Testing suspend to disk (STD) + +To verify that the STD works, you can try to suspend in the "reboot" mode: + +# echo reboot > /sys/power/disk +# echo disk > /sys/power/state + +and the system should suspend, reboot, resume and get back to the command prompt +where you have started the transition. If that happens, the STD is most likely +to work correctly, but you need to repeat the test at least a couple of times in +a row for confidence. This is necessary, because some problems only show up on +a second attempt at suspending and resuming the system. You should also test +the "platform" and "shutdown" modes of suspend: + +# echo platform > /sys/power/disk +# echo disk > /sys/power/state + +or + +# echo shutdown > /sys/power/disk +# echo disk > /sys/power/state + +in which cases you will have to press the power button to make the system +resume. If that does not work, you will need to identify what goes wrong. + +a) Test mode of STD + +To verify if there are any drivers that cause problems you can run the STD +in the test mode: + +# echo test > /sys/power/disk +# echo disk > /sys/power/state + +in which case the system should freeze tasks, suspend devices, disable nonboot +CPUs (if any), wait for 5 seconds, enable nonboot CPUs, resume devices, thaw +tasks and return to your command prompt. If that fails, most likely there is +a driver that fails to either suspend or resume (in the latter case the system +may hang or be unstable after the test, so please take that into consideration). +To find this driver, you can carry out a binary search according to the rules: +- if the test fails, unload a half of the drivers currently loaded and repeat +(that would probably involve rebooting the system, so always note what drivers +have been loaded before the test), +- if the test succeeds, load a half of the drivers you have unloaded most +recently and repeat. + +Once you have found the failing driver (there can be more than just one of +them), you have to unload it every time before the STD transition. In that case +please make sure to report the problem with the driver. + +It is also possible that a cycle can still fail after you have unloaded +all modules. In that case, you would want to look in your kernel configuration +for the drivers that can be compiled as modules (testing again with them as +modules), and possibly also try boot time options such as "noapic" or "noacpi". + +b) Testing minimal configuration + +If the test mode of STD works, you can boot the system with "init=/bin/bash" +and attempt to suspend in the "reboot", "shutdown" and "platform" modes. If +that does not work, there probably is a problem with a driver statically +compiled into the kernel and you can try to compile more drivers as modules, +so that they can be tested individually. Otherwise, there is a problem with a +modular driver and you can find it by loading a half of the modules you normally +use and binary searching in accordance with the algorithm: +- if there are n modules loaded and the attempt to suspend and resume fails, +unload n/2 of the modules and try again (that would probably involve rebooting +the system), +- if there are n modules loaded and the attempt to suspend and resume succeeds, +load n/2 modules more and try again. + +Again, if you find the offending module(s), it(they) must be unloaded every time +before the STD transition, and please report the problem with it(them). + +c) Advanced debugging + +In case the STD does not work on your system even in the minimal configuration +and compiling more drivers as modules is not practical or some modules cannot +be unloaded, you can use one of the more advanced debugging techniques to find +the problem. First, if there is a serial port in your box, you can set the +CONFIG_DISABLE_CONSOLE_SUSPEND kernel configuration option and try to log kernel +messages using the serial console. This may provide you with some information +about the reasons of the suspend (resume) failure. Alternatively, it may be +possible to use a FireWire port for debugging with firescope +(ftp://ftp.firstfloor.org/pub/ak/firescope/). On i386 it is also possible to +use the PM_TRACE mechanism documented in Documentation/s2ram.txt . + +2. Testing suspend to RAM (STR) + +To verify that the STR works, it is generally more convenient to use the s2ram +tool available from http://suspend.sf.net and documented at +http://en.opensuse.org/s2ram . However, before doing that it is recommended to +carry out the procedure described in section 1. + +Assume you have resolved the problems with the STD and you have found some +failing drivers. These drivers are also likely to fail during the STR or +during the resume, so it is better to unload them every time before the STR +transition. Now, you can follow the instructions at +http://en.opensuse.org/s2ram to test the system, but if it does not work +"out of the box", you may need to boot it with "init=/bin/bash" and test +s2ram in the minimal configuration. In that case, you may be able to search +for failing drivers by following the procedure analogous to the one described in +1b). If you find some failing drivers, you will have to unload them every time +before the STR transition (ie. before you run s2ram), and please report the +problems with them. diff --git a/Documentation/power/drivers-testing.txt b/Documentation/power/drivers-testing.txt new file mode 100644 index 000000000000..33016c2f18dd --- /dev/null +++ b/Documentation/power/drivers-testing.txt @@ -0,0 +1,42 @@ +Testing suspend and resume support in device drivers + (C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL + +1. Preparing the test system + +Unfortunately, to effectively test the support for the system-wide suspend and +resume transitions in a driver, it is necessary to suspend and resume a fully +functional system with this driver loaded. Moreover, that should be done +several times, preferably several times in a row, and separately for the suspend +to disk (STD) and the suspend to RAM (STR) transitions, because each of these +cases involves different ordering of operations and different interactions with +the machine's BIOS. + +Of course, for this purpose the test system has to be known to suspend and +resume without the driver being tested. Thus, if possible, you should first +resolve all suspend/resume-related problems in the test system before you start +testing the new driver. Please see Documents/power/basic-pm-debugging.txt for +more information about the debugging of suspend/resume functionality. + +2. Testing the driver + +Once you have resolved the suspend/resume-related problems with your test system +without the new driver, you are ready to test it: + +a) Build the driver as a module, load it and try the STD in the test mode (see: +Documents/power/basic-pm-debugging.txt, 1a)). + +b) Load the driver and attempt to suspend to disk in the "reboot", "shutdown" +and "platform" modes (see: Documents/power/basic-pm-debugging.txt, 1). + +c) Compile the driver directly into the kernel and try the STD in the test mode. + +d) Attempt to suspend to disk with the driver compiled directly into the kernel +in the "reboot", "shutdown" and "platform" modes. + +e) Attempt to suspend to RAM using the s2ram tool with the driver loaded (see: +Documents/power/basic-pm-debugging.txt, 2). As far as the STR tests are +concerned, it should not matter whether or not the driver is built as a module. + +Each of the above tests should be repeated several times and the STD tests +should be mixed with the STR tests. If any of them fails, the driver cannot be +regarded as suspend/resume-safe. |