Hi Jacopo, On Tue, Sep 10, 2024 at 11:19:57AM +0200, Jacopo Mondi wrote: > Hi Sakari, Tomi > > On Mon, Sep 09, 2024 at 03:52:42PM GMT, Sakari Ailus wrote: > > Hi Laurent, > > > > On Mon, Sep 09, 2024 at 04:45:16PM +0300, Laurent Pinchart wrote: > > > On Mon, Sep 09, 2024 at 03:29:30PM +0200, Jacopo Mondi wrote: > > > > On Mon, Sep 09, 2024 at 01:04:35PM GMT, Tomi Valkeinen wrote: > > > > > On 09/09/2024 12:13, Jacopo Mondi wrote: > > > > > > On Mon, Sep 09, 2024 at 08:22:59AM GMT, Tomi Valkeinen wrote: > > > > > > > On 09/09/2024 08:08, Tomi Valkeinen wrote: > > > > > > > > On 05/09/2024 14:11, Laurent Pinchart wrote: > > > > > > > > > On Thu, Sep 05, 2024 at 06:50:48PM +0800, kernel test robot wrote: > > > > > > > > > > Hi Tomi, > > > > > > > > > > > > > > > > > > > > kernel test robot noticed the following build warnings: > > > > > > > > > > > > > > > > > > > > [auto build test WARNING on 431c1646e1f86b949fa3685efc50b660a364c2b6] > > > > > > > > > > > > > > > > > > > > url: https://github.com/intel-lab-lkp/linux/commits/Tomi- > > > > > > > > > > Valkeinen/media-uapi-Add-meta-formats-for-PiSP-FE-config-and- > > > > > > > > > > stats/20240904-192729 > > > > > > > > > > base: 431c1646e1f86b949fa3685efc50b660a364c2b6 > > > > > > > > > > patch link: https://lore.kernel.org/r/20240904-rp1-cfe-v4-3- > > > > > > > > > > f1b5b3d69c81%40ideasonboard.com > > > > > > > > > > patch subject: [PATCH v4 3/4] media: raspberrypi: Add support > > > > > > > > > > for RP1-CFE > > > > > > > > > > config: m68k-allmodconfig (https://download.01.org/0day-ci/ > > > > > > > > > > archive/20240905/202409051822.ZzUGw3XQ-lkp@xxxxxxxxx/config) > > > > > > > > > > compiler: m68k-linux-gcc (GCC) 14.1.0 > > > > > > > > > > reproduce (this is a W=1 build): > > > > > > > > > > (https://download.01.org/0day-ci/ > > > > > > > > > > archive/20240905/202409051822.ZzUGw3XQ-lkp@xxxxxxxxx/reproduce) > > > > > > > > > > > > > > > > > > > > If you fix the issue in a separate patch/commit (i.e. not just a > > > > > > > > > > new version of > > > > > > > > > > the same patch/commit), kindly add following tags > > > > > > > > > > | Reported-by: kernel test robot <lkp@xxxxxxxxx> > > > > > > > > > > | Closes: https://lore.kernel.org/oe-kbuild- > > > > > > > > > > all/202409051822.ZzUGw3XQ-lkp@xxxxxxxxx/ > > > > > > > > > > > > > > > > > > > > All warnings (new ones prefixed by >>): > > > > > > > > > > > > > > > > > > > > > > drivers/media/platform/raspberrypi/rp1-cfe/cfe.c:2445:12: > > > > > > > > > > > > warning: 'cfe_runtime_resume' defined but not used > > > > > > > > > > > > [-Wunused-function] > > > > > > > > > > 2445 | static int cfe_runtime_resume(struct device *dev) > > > > > > > > > > | ^~~~~~~~~~~~~~~~~~ > > > > > > > > > > > > drivers/media/platform/raspberrypi/rp1-cfe/cfe.c:2435:12: > > > > > > > > > > > > warning: 'cfe_runtime_suspend' defined but not used > > > > > > > > > > > > [-Wunused-function] > > > > > > > > > > 2435 | static int cfe_runtime_suspend(struct device *dev) > > > > > > > > > > | ^~~~~~~~~~~~~~~~~~~ > > > > > > > > > > vim +/cfe_runtime_resume +2445 > > > > > > > > > > drivers/media/platform/raspberrypi/ rp1-cfe/cfe.c > > > > > > > > > > > > > > > > > > The recommended way to fix this is to switch from SET_RUNTIME_PM_OPS() > > > > > > > > > to RUNTIME_PM_OPS() and use pm_ptr() to set .driver.pm. This being said, > > > > > > > > > the driver won't work on a kernel with !CONFIG_PM given how you > > > > > > > > > implemented probe() and remove(). > > > > > > > > > > > > > > > > > > The pisp-be driver suffered from the same issue and Jacopo fixed it in > > > > > > > > > the last version. You can have a look at implement something similar. > > > > > > > > > > > > > > > > I can't right away think of any reason to not just depend on CONFIG_PM > > > > > > > > and be done with it without any tricks. Do you know if there's a reason? > > > > > > > > > > > > We had the same discussion, and even if I would be fine depending on > > > > > > CONFIG_PM, supporting !CONFIG_PM is not that much work, I kept it as > > > > > > an optional dependency (it was suggested during the review as well) > > > > > > > > > > > > > > > > > > > > Also, I don't think pisp-be is correct. It just calls > > > > > > > pispbe_runtime_resume() in probe() to wake the IP up (which only enables > > > > > > > pisp clock), without telling the runtime PM about it. This means the parent > > > > > > > device and the suppliers may not be powered up. > > > > > > > > > > > > Are you referring to the code currently in the tree or to this patch ? > > > > > > https://patchwork.linuxtv.org/project/linux-media/patch/20240904095836.344833-5-jacopo.mondi@xxxxxxxxxxxxxxxx/ > > > > > > > > > > Ah, I missed that one. > > > > > > > > > > I don't think it fixes the issue I mentioned. If we have PM enabled, and the > > > > > parent device requires powering up for the child device (BE) to be > > > > > accessible, the driver will crash when calling pispbe_hw_init(). I think you > > > > > should call pm_runtime_set_active() before calling pispbe_runtime_resume(). > > > > > > > > As discussed, this is not a problem currently for BE, but indeed you > > > > have a point. > > I admit the runtime_pm intrinsics are obscure to me, but Laurent just > made me notice something. > > Consider the following scenario > > *) Kernel compiled with CONFIG_PM > *) i2c sensor driver that supports both CONFIG_PM and !CONFIG_PM by: > *) Manually power up the sensor during probe > *) Call pm_runtime_enable() and pm_runtime_set_active() at the end > of the probe routine after having accessed the chip over i2c > (like most, if not all the i2c drivers in mainline do including > ccs) > > All these drivers work, and during the probe routine before accessing > the HW, they don't need to power up the parent i2c controller. This isn't done explicitly by the I²C drivers, indeed but... > > Might it be that during probe() the parent is guaranteed to be enabled ? ...yes. > > I add a look in the driver-core and pm Documentation/ but found > nothing. > > A quick stroll in driver/base/ got me to __device_attach() and it > seems parents are powered up before attaching a driver to a device > (which in my understanding should be what ends up calling probe()). > Clearly I've no real understanding of what I'm talking about when it > comes to driver-core, so take this with a grain of salt. This only works with runtime PM enabled. > > > > > > > > > Sad note: most of all the occurrences of "grep set_active" in > > > > drivers/media/platform/ show that set_active() is used as I've done in > > > > my patch > > > > > > > > > However, you said above that "supporting !CONFIG_PM is not that much work". > > > > > Maybe not. But how much work is it to get it right (for both PM and !PM), > > > > > and make sure it stays right? =). > > > > > > > > > > Just my opinion, but if there are zero use cases for the !PM, I would just > > > > > go with "depends on PM" to keep the driver simpler, less bug-prone, and > > > > > easier to maintain. > > > > > > I'm fine with that, and for platform drivers, that's my preferred > > > option. Sakari ? > > > > I'm concerned with your (?) recent finding that many architectures don't > > have support for CONFIG_PM. In this case the device is very unlikely to be > > used outside ARM(64) so I guess it's fine. > > > > Also, this IP is RPi specific, and the !CONFIG_PM case is not used or > tested on Pi. > > However, I think this current patch is correct (assuming the above > reasoning on i2c sensor drivers is correct) and doesn't require > CONFIG_PM, so I would be tempted to keep this version. I understand the current patch does depend on CONFIG_PM: it requires runtime PM to be operational to start the clock, for instance. > > > > > > > > I don't see a use case for !PM and we confirmed with RPi they don't > > > > need to support it. During the review of a previous version of the BE > > > > driver iirc I've been asked to support !PM but I'm not sure I recall > > > > the reasons. > > > > > > I hope it wasn't me :-) > > > > Me neither. Although it'd be nice: CONFIG_PM isn't a hardware specific > > option as such. As one part of the kernel requires !CONFIG_PM and another > > CONFIG_PM, we can expect problems, at least in principle. > > > > Ideally all architectures would support it so CONFIG_PM could be removed > > and we could say the problem has been solved. :-) -- Kidnregards, Sakari Ailus
