From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chanwoo Choi Subject: Re: Bug with dwc3 id detect and regulators Date: Thu, 14 Jun 2018 10:20:37 +0900 Message-ID: <5B21C2E5.2090004@samsung.com> References: <941bfd38-e975-e460-81aa-ce8d90c7a3f5@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8BIT Return-path: In-reply-to: <941bfd38-e975-e460-81aa-ce8d90c7a3f5@ti.com> Sender: linux-kernel-owner@vger.kernel.org To: Roger Quadros , "H. Nikolaus Schaller" , Tony Lindgren , Kishon Vijay Abraham I Cc: Discussions about the Letux Kernel , kernel@pyra-handheld.com, linux-omap , "linux-kernel@vger.kernel.org" List-Id: linux-omap@vger.kernel.org Hi Roger, On 2018년 06월 11일 17:53, Roger Quadros wrote: > Chanwoo, > > On 11/06/18 11:33, H. Nikolaus Schaller wrote: >> Hi Tony, >> another bug... >> >> [ 174.540313] BUG: scheduling while atomic: kworker/0:4/1327/0x00000002 >> [ 174.547353] Modules linked in: omapdrm drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops drm drm_panel_orientation_quirks bnep bluetooth ecdh_generic usb_f_ecm g_ether usb_f_rndis u_ether libcomposite configfs ipv6 arc4 wl18xx wlcore mac80211 panel_boe_w677l snd_soc_omap_hdmi_audio snd_soc_dmic cfg80211 dwc3 snd_soc_omap_abe_twl6040 snd_soc_twl6040 leds_gpio wwan_on_off connector_hdmi omapdss encoder_tpd12s015 cec pwm_omap_dmtimer omapdss_base pwm_bl generic_adc_battery ehci_omap wlcore_sdio dwc3_omap bmp280_spi snd_soc_ts3a227e crtouch_mt leds_is31fl319x tsc2007 bq2429x_charger bq27xxx_battery_i2c bq27xxx_battery ina2xx as5013 tca8418_keypad twl6040_vibra palmas_pwrbutton gpio_twl6040 palmas_gpadc usb3503 bmp280_i2c bmc150_accel_i2c w2cbw003_bluetooth bmc150_magn_i2c bmp2 80 bmc150_accel_core >> [ 174.624601] bmc150_magn bno055 industrialio_triggered_buffer kfifo_buf industrialio snd_soc_omap_mcbsp snd_soc_omap_mcpdm snd_soc_omap snd_pcm_dmaengine [last unloaded: syscopyarea] >> [ 174.642327] CPU: 0 PID: 1327 Comm: kworker/0:4 Tainted: G W 4.17.0-letux+ #2408 >> [ 174.651541] Hardware name: Generic OMAP5 (Flattened Device Tree) >> [ 174.658004] Workqueue: events_power_efficient palmas_gpio_id_detect >> [ 174.664780] [] (unwind_backtrace) from [] (show_stack+0x10/0x14) >> [ 174.673109] [] (show_stack) from [] (dump_stack+0x7c/0x9c) >> [ 174.680881] [] (dump_stack) from [] (__schedule_bug+0x60/0x84) >> [ 174.689006] [] (__schedule_bug) from [] (__schedule+0x50/0x694) >> [ 174.697217] [] (__schedule) from [] (schedule+0xb0/0xcc) >> [ 174.704790] [] (schedule) from [] (schedule_timeout+0x354/0x3d4) >> [ 174.713100] [] (schedule_timeout) from [] (wait_for_common+0x118/0x158) >> [ 174.722064] [] (wait_for_common) from [] (omap_i2c_xfer+0x354/0x48c) >> [ 174.730749] [] (omap_i2c_xfer) from [] (__i2c_transfer+0x238/0x550) >> [ 174.739350] [] (__i2c_transfer) from [] (i2c_transfer+0x84/0xb4) >> [ 174.747685] [] (i2c_transfer) from [] (bq24296_i2c_reg8_read.constprop.8+0x54/0x64 [bq2429x_charger]) >> [ 174.759465] [] (bq24296_i2c_reg8_read.constprop.8 [bq2429x_charger]) from [] (bq24296_update_reg+0x28/0xf8 [bq2429x_charger]) >> [ 174.773437] [] (bq24296_update_reg [bq2429x_charger]) from [] (_regulator_do_disable+0x100/0x238) >> [ 174.784804] [] (_regulator_do_disable) from [] (_regulator_disable+0x88/0x120) >> [ 174.794404] [] (_regulator_disable) from [] (regulator_disable+0x30/0x60) >> [ 174.803556] [] (regulator_disable) from [] (dwc3_omap_set_mailbox+0x84/0xf8 [dwc3_omap]) >> [ 174.814124] [] (dwc3_omap_set_mailbox [dwc3_omap]) from [] (dwc3_omap_id_notifier+0x14/0x1c [dwc3_omap]) >> [ 174.826149] [] (dwc3_omap_id_notifier [dwc3_omap]) from [] (notifier_call_chain+0x40/0x68) >> [ 174.836867] [] (notifier_call_chain) from [] (raw_notifier_call_chain+0x14/0x1c) >> [ 174.846661] [] (raw_notifier_call_chain) from [] (extcon_sync+0x54/0x19c) >> [ 174.855804] [] (extcon_sync) from [] (process_one_work+0x244/0x464) >> [ 174.864386] [] (process_one_work) from [] (worker_thread+0x2c0/0x3ec) >> [ 174.873156] [] (worker_thread) from [] (kthread+0x134/0x150) >> [ 174.881087] [] (kthread) from [] (ret_from_fork+0x14/0x2c) >> >> It turns out that extcon_sync() holds a spinlock while sending its notifiers and this >> is ending up in our regulator.en/disable() which wants to use blocking i2c. >> >> Do you see similar things on the OMAP5EVM when using OTG mode? >> The Palmas SMPS10 is also handled through i2c. Or is this magically hidden by regmap? >> >> Well, as a workaround, I can make the regulator.en/disable() in the bq2429x driver >> just trigger a worker, but IMHO it is not expected for regulator ops to be spinlock safe. >> >> So I think extcon should not spinlock (which might be against the extcon design) or > > I think this something that should be addressed in the Extcon layer. > Do you really need to call the raw_notifier_call_chain() function with spinlock held in extcon_sync()? > if yes why? To reduce the latency of notification is important of extcon. So, extcon used the spinlock before calling the notifier_call_chain to prevent the scheduled out for a moment. Also, the notifier_call calls the registered notifier function sequentially. It means that if some registered notifier function spends a lot of time, the next registered notifier might receive the notification with a delay. So, extcon used the spinlock. Unitl now, But, as you commented and previously, sometimes it caused the similar issues. (To fix similar issues, the consumer device used the workqueue) I will call notifier function without spinlock as following and I'll consider the other way to notify the changed state to consumer device with broadcasting way. diff --git a/drivers/extcon/extcon.c b/drivers/extcon/extcon.c index 8bff5fd18185..1e35b8ca3951 100644 --- a/drivers/extcon/extcon.c +++ b/drivers/extcon/extcon.c @@ -433,8 +433,8 @@ int extcon_sync(struct extcon_dev *edev, unsigned int id) return index; spin_lock_irqsave(&edev->lock, flags); - state = !!(edev->state & BIT(index)); + spin_unlock_irqrestore(&edev->lock, flags); /* * Call functions in a raw notifier chain for the specific one @@ -448,6 +448,8 @@ int extcon_sync(struct extcon_dev *edev, unsigned int id) */ raw_notifier_call_chain(&edev->nh_all, state, edev); + spin_lock_irqsave(&edev->lock, flags); + > > I think we don't want to call all notifiers in atomic context as this would keep interrupts disabled > for quite some time and is suboptimal. > >> dwc3_omap_set_mailbox should move dis/enabling regulator to some worker thread so >> that they can block. >> >> The best would be to make dwc3_omap_set_mailbox call regulator_enable_deferred(omap->vbus_reg, 0) >> but that function does not exist. >> >> Any ideas? >> >> BR, >> Nikolaus >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-omap" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > -- Best Regards, Chanwoo Choi Samsung Electronics