On 22-7-2016 12:26, Stanislaw Gruszka wrote: > On Fri, Jul 22, 2016 at 10:38:24AM +0200, Arend Van Spriel wrote: >> + Luis >> >> On 21-7-2016 13:51, Stanislaw Gruszka wrote: >>> (cc: firmware and brcmfmac maintainers) >>> >>> On Thu, Jul 21, 2016 at 06:23:11AM -0400, Prarit Bhargava wrote: >>>> >>>> >>>> On 07/21/2016 04:05 AM, Stanislaw Gruszka wrote: >>>>> On Thu, Jul 21, 2016 at 10:36:42AM +0300, Emmanuel Grumbach wrote: >>>>>> On Thu, Jul 21, 2016 at 10:09 AM, Stanislaw Gruszka <sgruszka@xxxxxxxxxx> wrote: >>>>>>> On Tue, Jul 19, 2016 at 03:00:37PM +0200, Michal Kazior wrote: >>>>>>>> Firmware files are versioned to prevent older >>>>>>>> driver instances to load unsupported firmware >>>>>>>> blobs. This is reflected with a fallback logic >>>>>>>> which attempts to load several firmware files. >>>>>>>> >>>>>>>> This however produced a lot of unnecessary >>>>>>>> warnings sometimes confusing users and leading >>>>>>>> them to rename firmware files making things even >>>>>>>> more confusing. >>>>>>> >>>>>>> This happens on kernels configured with >>>>>>> CONFIG_FW_LOADER_USER_HELPER_FALLBACK and cause not only ugly warnings, >>>>>>> but also 60 seconds delay before loading next firmware version. >>>>>>> For some reason RHEL kernel needs above config option, so this >>>>>>> patch is very welcome from my perspective. >>>>>>> >>>>>> >>>>>> Sorry for my ignorance but how does the firmware loading work if not >>>>>> with udev's help? >>>>> >>>>> I'm not sure exactly, but I think kernel VFS layer is capable to copy >>>>> file data directly from mounted filesystem without user space helper. >>>> >>>> Here's the situation: request_firmware() waits 60 seconds for udev to do its >>>> loading magic via a "usermode helper". This delay is there to allow, for >>>> example, userspace to unpack or download a new firmware image or verify the >>>> firmware image *in userspace* before providing it to the driver to apply to the HW. >>>> >>>> Why 60 seconds? It is arbitrary and there is no way for udev & the kernel to >>>> handshake on completion. >>>> >>>>> >>>>>> As you can imagine, iwlwifi is suffering from the >>>>>> same problem and I would be interested in applying the same change, >>>>>> but I'd love to understand a bit more :) >>>>> >>>>> Yes, iwlwifi (and some other drivers) suffer from this. However this >>>>> happen when the newest firmware version is not installed on the system >>>>> and CONFIG_FW_LOADER_USER_HELPER_FALLBACK is enabled. What I suppose >>>>> it's not common. >>>> >>>> request_firmware_direct() was introduced at my request because (as you've >>>> noticed) when CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y drivers may stall for long >>>> periods of time when starting. The bug that this introduced was a 60 second >>>> delay per logical cpu when starting a system. On a 64 cpu system that meant the >>>> boot would complete in a little over one hour. >>>> >>>>> >>>>> I started to see this currently, because that option was enabled on >>>>> RHEL kernel. BTW: I think Prarit iwlwifi thermal_zone problem was >>>>> happened because of that, i.e. thermal device was not functional >>>>> because f/w wasn't loaded due to big delay. >>>>> >>>>> I'm not sure if replacing to request_firmware_direct() is a good >>>>> fix though. For example I can see this problem also on brcmfmac, which >>>>> use request_firmware_nowait(). I think I would rather prefer special >>>>> helper for firmware drivers that needs user helper and have >>>>> request_firmware() be direct as default. >>>>> >>>> >>>> The difference between request_firmware_direct() and request_firmware() is that >>>> the _direct() version does not wait the 60 seconds for udev interaction. The >>>> only userspace check performed is to see if the file is there, and if the file >>>> does exist it is provided to the driver to be applied to the hardware. >>>> >>>> So the real question to ask here is whether or not the ath10k, brcmfmac, and >>>> iwlwifi require udev to do anything beyond checking for the existence and >>>> loading the firmware image. If they don't, then it is better to use >>>> request_firmware_direct(). >>> >>> They don't need that, like 99% of the drivers I think, hence changing the >>> default seems to be more reasonable. However changing 3 drivers would work >>> for me as well, and that change do not introduce risk of broking drivers >>> that require udev fw download. >>> >>> iwlwifi and ath10k are trivial, bcrmfmac is a bit more complex as it >>> use request_firmware_nowait(), so it first need to be converted to >>> ordinary request_firmware(), but this should be doable and I can do >>> that. >> >> I am going bonkers here. This is the Nth time a discussion pops up on >> firmware API usage. I stopped counting N :-( So the first issue was that >> the INIT was taking to long as we were requesting firmware during probe >> which was executed in the INIT context. So we added a worker and >> register the driver from there. There was probably a reason for >> switching to _no_wait() as well, but I do not recall the details. The >> things is I don't know if I need user-space or not. I just need firmware >> to get the device up and running. We have changed our driver a couple of >> times now to accommodate something that in my opinion should have been >> abstracted behind the firmware API in the first place and now here is >> another proposal to change the drivers. Come on! > > I understand you dislike that :-) Just to clarify the issue here: > > Some drivers (including brcmfmac) request new firmware images, which are > not yet available (i.e. development F/W versions) and then fall-back > to older firmware version and works perfectly fine. > > However with CONFIG_FW_LOADER_USER_HELPER_FALLBACK=y configured, in case > of missing F/W image, request firmware involve user space helper and > waits 60s (loading_timeout value from drivers/base/firmware_class.c), > what delays creating network interface and confuse users. > > For brcmfmac this looks like this: > > [ 15.160923] brcmfmac 0000:03:00.0: Direct firmware load for brcm/brcmfmac4356-pcie.txt failed with error -2 > [ 15.170759] brcmfmac 0000:03:00.0: Falling back to user helper > <snip> > [ 75.709397] brcmfmac: brcmf_c_preinit_dcmds: Firmware version = wl0: Oct 22 2015 06:16:41 version 7.35.180.119 (r594535) FWID 01-1a5c4016 > [ 75.736941] brcmfmac: brcmf_cfg80211_reg_notifier: not a ISO3166 code (0x30 0x30) > > Without CONFIG_FW_LOADER_USER_HELPER_FALLBACK first firmware request > silently fail and then instantly next F/W image is loaded. > > Another option to solve to problem would be stop requesting not > available publicly firmware. However, I assume some drivers would > like to preserve that option. Actually, this is not the case with brcmfmac. We do need a firmware file, ie. brcm/brcmfmac4356-pcie.bin, and also request for a nvram file, ie. brcm/brcmfmac4356-pcie.txt. The latter is optional and the device works fine without it. What is still unclear to me is when request_firmware_direct() would fail and in what circumstances the udev helper is a valid callback. Can you explain such a scenario. Another question I have is what the reasons are behind the 60 seconds timeout. >>> However I wonder if changing that will not broke the case when >>> driver is build-in in the kernel and f/w is not yet available when >>> driver start to initialize. Or maybe nowadays this is not the case >>> any longer, i.e. the MODULE_FIRMWARE macros assure proper f/w >>> images are build-in in the kernel or copied to initramfs? >> >> That is a nice idea, but I have not seen any change in that area. Could >> have missed it. > > I believe this is how the things are already done, IOW switching to > request_firmware_direct() in the driver should be no harm. Ok. What are the consequences when: - driver is built-in. - driver+firmware present on initramfs. - driver on initramfs, firmware only present on rootfs. - driver+firmware only on rootfs. I assume the third one would be considered a configuration issue. Regards, Arend -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
