From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tony Lindgren Subject: Re: [PATCH] usb-musb: keep VBUS on when device is disconnected Date: Thu, 11 May 2017 12:38:11 -0700 Message-ID: <20170511193810.GX3489@atomide.com> References: <20170327143049.GG10760@atomide.com> <63FD9E13-2B70-485C-80A7-206BEC16905A@tecnorama.it> <20170327165946.GL10760@atomide.com> <20170327171534.GA4403@uda0271908> <20170327175536.GP10760@atomide.com> <20170511185038.GE7154@uda0271908> <20170511185528.GW3489@atomide.com> <20170511190100.GF7154@uda0271908> <20170511191005.GG7154@uda0271908> <20170511192013.GA4459@uda0271908> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170511192013.GA4459@uda0271908> Sender: linux-kernel-owner@vger.kernel.org To: Bin Liu , Moreno Bartalucci , Lars Melin , "linux-omap@vger.kernel.org" , "linux-usb@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Alessio Igor Bogani List-Id: linux-omap@vger.kernel.org * Bin Liu [170511 12:23]: > On Thu, May 11, 2017 at 02:10:05PM -0500, Bin Liu wrote: > [...] > > > > > The otg state machine implementation in the musb drivers are kind of strange. > > > > > OTG_STATE_A_WAIT_BCON suppose to be a steady state when no usb device is > > > > > attached, but the musb drivers use it as a transient state to handle error > > > > > cases, such as overcurrent ot HNP timeout, which is done in the 'case > > > > > OTG_STATE_A_WAIT_BCON' branch in otg_timer() (or dsps_check_status() for dsps > > > > > glue). > > > > > > > > > > Then later when 2f3fd2c5bde1 adds > > > > > > > > > > - /* Poll for ID change in OTG port mode */ > > > > > - if (musb->xceiv->otg->state == OTG_STATE_B_IDLE && > > > > > - musb->port_mode == MUSB_PORT_MODE_DUAL_ROLE) > > > > > + /* Poll for ID change and connect */ > > > > > + switch (musb->xceiv->otg->state) { > > > > > + case OTG_STATE_B_IDLE: > > > > > + case OTG_STATE_A_WAIT_BCON: > > > > > mod_timer(&glue->timer, jiffies + > > > > > msecs_to_jiffies(wrp->poll_timeout)); > > > > > + break; > > > > > > > > > > which causes dsps_check_status (or otg_timer()) got called for a normal > > > > > condition with OTG_STATE_A_WAIT_BCON, then turns off VBUS... > > > > > > > > > > Will try to see how to solve this... > > > > > > > > Maybe we just need to add back the earlier check for non-OTG devices > > > > "musb->port_mode == MUSB_PORT_MODE_DUAL_ROLE" into case > > > > OTG_STATE_A_WAIT_BCON? > > > > > > Not sure if it will work. The check is to kick out device-only mode. > > > DUAL_ROLE means both OTG and host-only. > > > > > > > > > > > Not sure if am335x configured with host port ever idle that way, > > > > but maybe VBUS can be kept on with musb idle. > > > > > > Just tried to remove > > > > > > + case OTG_STATE_A_WAIT_BCON: > > > > > > for the polling, but the port stops detecting device attach, musb > > > power/devctl registers are good, trying to see why... maybe related to > > > PM state? > > > > usb_otg_hs is idle, so not able to detect attach. So need to get the > > timer rolling in here to make it detect working. > > Maybe need to add a flag in dsps_check_status() to not turn off vbus in > > this case? Really don't like the idea... Yeah that's what I recall too. The timer is needed until the m3 can implement an irqchip and we can set that up as the irq for the host only port. > I am not sure I gave out the picture clearly. > > Before added the runtime PM support, in host mode (devctl=0x19) the > otg_timer is stopped, the controller is ready to detect attach. > > Later when added the runtime PM support, usb_otg_hs hwmod becomes idle > when a device is detached, so the otg_timer is needed to keep hwmod > enable/idle periodically to detect attach, which triggers the issue > because otg_timer() turns off vbus unconditionally when otg state is > OTG_STATE_A_WAIT_BCON. I wonder if just keeping VBUS on longer in OTG_STATE_A_WAIT_BCON solves this issue? It seems the issue is with modems that get reconfigured after the initial enumeration? We could poll for new devices every 2 seconds, if anything is seen on the bus, keep VBUS on at least 20 seconds, then if nothing is found, poll every 2 seconds again. Regards, Tony