From mboxrd@z Thu Jan 1 00:00:00 1970 From: peter.chen@nxp.com (Peter Chen) Date: Tue, 9 Aug 2016 00:42:07 +0000 Subject: [PATCH v2 08/22] usb: chipidea: Remove locking in ci_udc_start() In-Reply-To: <147070007426.10825.11324896309403492272@sboyd-linaro> References: <20160707222114.1673-1-stephen.boyd@linaro.org> <20160707222114.1673-9-stephen.boyd@linaro.org> <20160708094528.GF20485@shlinux2> <147043403652.26915.10865210145828633146@sboyd-linaro> <20160806075435.GB12298@shlinux2> <147070007426.10825.11324896309403492272@sboyd-linaro> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org >Quoting Peter Chen (2016-08-06 00:54:35) >> On Fri, Aug 05, 2016 at 02:53:56PM -0700, Stephen Boyd wrote: >> > Quoting Peter Chen (2016-07-08 02:45:28) >> > > On Thu, Jul 07, 2016 at 03:20:59PM -0700, Stephen Boyd wrote: >> > > > We don't call hw_device_reset() with the ci->lock held, so it >> > > > doesn't seem like this lock here is protecting anything. Let's >> > > > just remove it. This allows us to call sleeping functions like >> > > > phy_init() from within the CI_HDRC_CONTROLLER_RESET_EVENT hook. >> > > > >> > > > Cc: Peter Chen >> > > > Cc: Greg Kroah-Hartman >> > > > Signed-off-by: Stephen Boyd >> > > > --- >> > > > drivers/usb/chipidea/udc.c | 3 --- >> > > > 1 file changed, 3 deletions(-) >> > > > >> > > > diff --git a/drivers/usb/chipidea/udc.c >> > > > b/drivers/usb/chipidea/udc.c index 065f5d97aa67..f16be4710cdb >> > > > 100644 >> > > > --- a/drivers/usb/chipidea/udc.c >> > > > +++ b/drivers/usb/chipidea/udc.c >> > > > @@ -1719,7 +1719,6 @@ static int ci_udc_start(struct usb_gadget *gadget, >> > > > struct usb_gadget_driver *driver) { >> > > > struct ci_hdrc *ci = container_of(gadget, struct ci_hdrc, gadget); >> > > > - unsigned long flags; >> > > > int retval = -ENOMEM; >> > > > >> > > > if (driver->disconnect == NULL) @@ -1746,7 +1745,6 @@ >> > > > static int ci_udc_start(struct usb_gadget *gadget, >> > > > >> > > > pm_runtime_get_sync(&ci->gadget.dev); >> > > > if (ci->vbus_active) { >> > > > - spin_lock_irqsave(&ci->lock, flags); >> > > > hw_device_reset(ci); >> > > > } else { >> > > > usb_udc_vbus_handler(&ci->gadget, false); @@ >> > > > -1755,7 +1753,6 @@ static int ci_udc_start(struct usb_gadget *gadget, >> > > > } >> > > > >> > > > retval = hw_device_state(ci, ci->ep0out->qh.dma); >> > > > - spin_unlock_irqrestore(&ci->lock, flags); >> > > > if (retval) >> > > > pm_runtime_put_sync(&ci->gadget.dev); >> > > > >> > > >> > > The main purpose for this is disabling interrupt when reset >> > > controller, in case the unexpected interrupts occur. >> > > >> > > You can move this between hw_device_state. >> > > >> > >> > Ok, but we don't hold the ci->lock in ci_udc_vbus_session(). Is that >> > a bug as well? >> >> I agree with your patch. In fact, during the reset controller, the >> interrupt has not been enabled, it should no unexpected interrupt. >> > >So then we can leave this patch as is? It still isn't clear to me what sequence of >events that would cause a problem if we don't hold the >ci->lock around hw_device_state(). Yes. I am ok with this patch. After thinking more, it is safe to be without lock. And we have this unlock code in nxp internal tree, and without any problems during 1-2 years. Acked-by: Peter Chen Peter