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[68.147.8.254]) by smtp.gmail.com with ESMTPSA id 82sm13322297pfy.24.2020.11.14.09.51.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 14 Nov 2020 09:51:46 -0800 (PST) Date: Sat, 14 Nov 2020 10:51:45 -0700 From: Mathieu Poirier To: Arnaud POULIQUEN Cc: Guennadi Liakhovetski , "ohad@wizery.com" , "bjorn.andersson@linaro.org" , "linux-remoteproc@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v5 8/8] rpmsg: Turn name service into a stand alone driver Message-ID: <20201114175145.GC3583825@xps15> References: <20201105225028.3058818-9-mathieu.poirier@linaro.org> <20201106131545.GA10889@ubuntu> <20201106140028.GB10889@ubuntu> <20201106175332.GB3203364@xps15> <20201109102023.GA17692@ubuntu> <20201109175536.GD3395222@xps15> <7be438d7-1a33-8d5c-1c8b-8838bef83e97@st.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7be438d7-1a33-8d5c-1c8b-8838bef83e97@st.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 12, 2020 at 10:04:17AM +0100, Arnaud POULIQUEN wrote: > > > On 11/11/20 1:37 AM, Mathieu Poirier wrote: > > On Tue, 10 Nov 2020 at 11:18, Arnaud POULIQUEN wrote: > >> > >> Hi Mathieu, Guennadi, > >> > >> On 11/9/20 6:55 PM, Mathieu Poirier wrote: > >>> On Mon, Nov 09, 2020 at 11:20:24AM +0100, Guennadi Liakhovetski wrote: > >>>> Hi Arnaud, > >>>> > >>>> On Mon, Nov 09, 2020 at 09:48:37AM +0100, Arnaud POULIQUEN wrote: > >>>>> Hi Guennadi, Mathieu, > >>>>> > >>>>> On 11/6/20 6:53 PM, Mathieu Poirier wrote: > >>>>>> On Fri, Nov 06, 2020 at 03:00:28PM +0100, Guennadi Liakhovetski wrote: > >>>>>>> On Fri, Nov 06, 2020 at 02:15:45PM +0100, Guennadi Liakhovetski wrote: > >>>>>>>> Hi Mathieu, Arnaud, > >>>>>>>> > >>>>>>>> On Thu, Nov 05, 2020 at 03:50:28PM -0700, Mathieu Poirier wrote: > >>>>>>>>> From: Arnaud Pouliquen > >>>>>>>>> > >>>>>>>>> Make the RPMSG name service announcement a stand alone driver so that it > >>>>>>>>> can be reused by other subsystems. It is also the first step in making the > >>>>>>>>> functionatlity transport independent, i.e that is not tied to virtIO. > >>>>>>>> > >>>>>>>> Sorry, I just realised that my testing was incomplete. I haven't tested > >>>>>>>> automatic module loading and indeed it doesn't work. If rpmsg_ns is loaded > >>>>>>>> it probes and it's working, but if it isn't loaded and instead the rpmsg > >>>>>>>> bus driver is probed (e.g. virtio_rpmsg_bus), calling > >>>>>>>> rpmsg_ns_register_device() to create a new rpmsg_ns device doesn't cause > >>>>>>>> rpmsg_ns to be loaded. > >>>>>>> > >>>>>>> A simple fix for that is using MODULE_ALIAS("rpmsg:rpmsg_ns"); in rpmsg_ns.c > >>>>>>> but that alone doesn't fix the problem completely - the module does load then > >>>>>>> but not quickly enough, the NS announcement from the host / remote arrives > >>>>>>> before rpmsg_ns has properly registered. I think the best solution would be > >>>>>>> to link rpmsg_ns.c together with rpmsg_core.c. You'll probably want to keep > >>>>>>> the module name, so you could rename them to just core.c and ns.c. > >>>>>> > >>>>>> I'm pretty sure it is because virtio_device_ready() in rpmsg_probe() is called > >>>>>> before the kernel has finished loading the name space driver. There has to be > >>>>>> a way to prevent that from happening - I will investigate further. > >>>>> > >>>>> Right, no dependency is set so the rpmsg_ns driver is never probed... > >>>>> And name service announcement messages are dropped if the service is not present. > >>>> > >>>> The mentioned change > >>>> > >>>> -MODULE_ALIAS("rpmsg_ns"); > >>>> +MODULE_ALIAS("rpmsg:rpmsg_ns"); > >>> > >>> Yes, I'm good with that part. > >>> > >>>> > >>>> is actually a compulsory fix, without it the driver doesn't even get loaded when > >>>> a device id registered, using rpmsg_ns_register_device(). So this has to be done > >>>> as a minimum *if* we keep RPNsg NS as a separate kernel module. However, that > >>>> still doesn't fix the problem relyably because of timing. I've merged both the > >>>> RPMsg core and NS into a single module, which fixed the issue for me. I'm > >>>> appending a patch to this email, but since it's a "fixup" please, feel free to > >>>> roll it into the original work. But thinking about it, even linking modules > >>>> together doesn't guarantee the order. I think rpmsg_ns_register_device() should > >>>> actually actively wait for NS device probing to finish - successfully or not. > >>>> I can add a complete() / wait_for_completion() pair to the process if you like. > >>>> > >>> > >>> Working with a completion is the kind of thing I had in mind. But I would still > >>> like to keep the drivers separate and that's the part I need to think about. > >> > >> I reproduce the problem: the rpmsg_ns might not be probed on first message reception. > >> What makes the fix not simple is that the virtio forces the virtio status to ready > >> after the probe of the virtio unit [1]. > >> Set this status tiggs the remote processor first messages. > >> > >> [1]https://elixir.bootlin.com/linux/latest/source/drivers/virtio/virtio.c#L253 > >> > >> Guennadi: I'm not sure that your patch will solve the problem , look like it just reduces the > >> delay between the rpmsg_virtio and the rpmsg_ns probe (the module loading time is saved) > >> > >> Based on my observations, I can see two alternatives. > >> - rpmsg_ns.c is no longer an rpmsg driver but a kind of function library to manage a generic name service. > > > > That option joins Guennadi's vision - I think he just expressed it in > > a different way. The more I think about it, the more I find that > > option appealing. With the code separation already achieved in this > > patchset it wouldn't be hard to implement. > > Right, similar to Guennadi's version, if we want to keep it simpler this is > probably the preferred option. > From my point of view the main requierement is that the ns announcement service > is generic. > > > > > >> - we implement a completion as proposed by Mathieu. > >> > >> I tried this second solution based on the component bind mechanism. > >> I added the patch at the end of the mail (the patch is a POC, so not ready for upstream). > >> Maybe something simpler is possible. I'm just keeping in mind that we may have to add similar > >> services in the future. > >> > > > > Wasn't familiar with the "component" infrastructure - I suppose you > > stumbled on it while working on sound drivers. I have to spend more > > time looking at it. > > Used in DRM framework mainly, i implemented this in my RFC[1] concerning the > refactoring of the rproc_virtio in a platform driver. The idea was to ensure > that all rproc sub-devices are registered before starting the remote processor. > > [1]https://lkml.org/lkml/2020/4/16/1817 > > The principle it to attach child components to a master component, this > relationship allows to synchronize all using component_master_add_with_match > and component_bind_all after the drivers probing step. > The drawback of this solution is that it make code more complex. > > > But if you have time and want to spin off a new > > revision that implements the library concept, I'll invest time on that > > instead. > > Time is always a major issue :) > No time this week, but i will try to send patches next week. I agree, I'm running short on it too. I thought what you pointed out with find_module() [1] was quite interesting. I tried it on my side but used request_module() rather than request_module_nowait() - because we do want to wait for the namespace driver to be loaded before moving forward. Unfortunatly the system hung on me... I still don't know why, I will have to investigate further. Regarding your patch on components, I am now up to speed with the concept. That too is interesting but likely an overkill for the current situation. Right now we have a single driver to deal with and I think we should keep things as simple as possible. I'll talk to you guys on Monday, Mathieu [1]. https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_fb_helper.c#L2274 > > Regards, > Arnaud > > > > >> Regards, > >> Arnaud > >> > >> From f2de77027f4a3836f8bf46aa257e5592af6529b7 Mon Sep 17 00:00:00 2001 > >> From: Arnaud Pouliquen > >> Date: Tue, 10 Nov 2020 18:39:29 +0100 > >> Subject: [PATCH] rpmsg_ns: add synchronization based on component mechanism > >> > >> Implement the component bind mechanism to ensure that the rpmsg virtio bus > >> driver are probed before treating the first RPMsg. > >> > >> Signed-off-by: Arnaud Pouliquen > >> --- > >> drivers/rpmsg/rpmsg_ns.c | 26 ++++++++++++- > >> drivers/rpmsg/virtio_rpmsg_bus.c | 65 ++++++++++++++++++++++++++++++++ > >> 2 files changed, 89 insertions(+), 2 deletions(-) > >> > >> diff --git a/drivers/rpmsg/rpmsg_ns.c b/drivers/rpmsg/rpmsg_ns.c > >> index 5bda7cb44618..057e5d1d29a0 100644 > >> --- a/drivers/rpmsg/rpmsg_ns.c > >> +++ b/drivers/rpmsg/rpmsg_ns.c > >> @@ -2,6 +2,7 @@ > >> /* > >> * Copyright (C) STMicroelectronics 2020 - All Rights Reserved > >> */ > >> +#include > >> #include > >> #include > >> #include > >> @@ -55,6 +56,24 @@ static int rpmsg_ns_cb(struct rpmsg_device *rpdev, void *data, int len, > >> return 0; > >> } > >> > >> +static int rpmsg_ns_bind(struct device *dev, struct device *master, void *data) > >> +{ > >> + dev_info(dev, "rpmsg ns bound\n"); > >> + > >> + return 0; > >> +} > >> + > >> +static void rpmsg_ns_unbind(struct device *dev, struct device *master, > >> + void *data) > >> +{ > >> + dev_info(dev, "rpmsg ns unbound\n"); > >> +} > >> + > >> +static const struct component_ops rpmsg_ns_ops = { > >> + .bind = rpmsg_ns_bind, > >> + .unbind = rpmsg_ns_unbind, > >> +}; > >> + > >> static int rpmsg_ns_probe(struct rpmsg_device *rpdev) > >> { > >> struct rpmsg_endpoint *ns_ept; > >> @@ -63,6 +82,7 @@ static int rpmsg_ns_probe(struct rpmsg_device *rpdev) > >> .dst = RPMSG_NS_ADDR, > >> .name = "name_service", > >> }; > >> + int ret; > >> > >> /* > >> * Create the NS announcement service endpoint associated to the RPMsg > >> @@ -76,7 +96,9 @@ static int rpmsg_ns_probe(struct rpmsg_device *rpdev) > >> } > >> rpdev->ept = ns_ept; > >> > >> - return 0; > >> + ret = component_add(&rpdev->dev, &rpmsg_ns_ops); > >> + > >> + return ret; > >> } > >> > >> static struct rpmsg_driver rpmsg_ns_driver = { > >> @@ -104,5 +126,5 @@ module_exit(rpmsg_ns_exit); > >> > >> MODULE_DESCRIPTION("Name service announcement rpmsg Driver"); > >> MODULE_AUTHOR("Arnaud Pouliquen "); > >> -MODULE_ALIAS("rpmsg_ns"); > >> +MODULE_ALIAS("rpmsg:rpmsg_ns"); > >> MODULE_LICENSE("GPL v2"); > >> diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c > >> index 30ef4a5de4ed..c28aac1295fa 100644 > >> --- a/drivers/rpmsg/virtio_rpmsg_bus.c > >> +++ b/drivers/rpmsg/virtio_rpmsg_bus.c > >> @@ -11,6 +11,7 @@ > >> > >> #define pr_fmt(fmt) "%s: " fmt, __func__ > >> > >> +#include > >> #include > >> #include > >> #include > >> @@ -67,11 +68,16 @@ struct virtproc_info { > >> struct mutex endpoints_lock; > >> wait_queue_head_t sendq; > >> atomic_t sleepers; > >> + struct component_match *match; > >> + struct completion completed; > >> + int bind_status; > >> }; > >> > >> /* The feature bitmap for virtio rpmsg */ > >> #define VIRTIO_RPMSG_F_NS 0 /* RP supports name service notifications */ > >> > >> +#define BIND_TIMEOUT_MS 1000 > >> + > >> /** > >> * struct rpmsg_hdr - common header for all rpmsg messages > >> * @src: source address > >> @@ -768,6 +774,17 @@ static void rpmsg_recv_done(struct virtqueue *rvq) > >> unsigned int len, msgs_received = 0; > >> int err; > >> > >> + /* Wait for all children to be bound */ > >> + if (vrp->bind_status) { > >> + dev_dbg(dev, "cwait bind\n"); > >> + if (!wait_for_completion_timeout(&vrp->completed, > >> + msecs_to_jiffies(BIND_TIMEOUT_MS))) > >> + dev_err(dev, "child device(s) binding timeout\n"); > >> + > >> + if (vrp->bind_status) > >> + dev_err(dev, "failed to bind RPMsg sub device(s)\n"); > >> + } > >> + > >> msg = virtqueue_get_buf(rvq, &len); > >> if (!msg) { > >> dev_err(dev, "uhm, incoming signal, but no used buffer ?\n"); > >> @@ -808,6 +825,39 @@ static void rpmsg_xmit_done(struct virtqueue *svq) > >> wake_up_interruptible(&vrp->sendq); > >> } > >> > >> +static int virtio_rpmsg_compare(struct device *dev, void *data) > >> +{ > >> + return dev == data; > >> +} > >> + > >> +static void virtio_rpmsg_unbind(struct device *dev) > >> +{ > >> + /* undbind all child components */ > >> + component_unbind_all(dev, NULL); > >> +} > >> + > >> +static int virtio_rpmsg_bind(struct device *dev) > >> +{ > >> + struct virtio_device *vdev = dev_to_virtio(dev); > >> + struct virtproc_info *vrp = vdev->priv; > >> + > >> + dev_dbg(dev, "Bind virtio rpmsg sub devices\n"); > >> + > >> + vdev = container_of(dev, struct virtio_device, dev); > >> + vrp->bind_status = component_bind_all(dev, NULL); > >> + if (vrp->bind_status) > >> + dev_err(dev, "bind virtio rpmsg failed\n"); > >> + > >> + complete(&vrp->completed); > >> + > >> + return vrp->bind_status; > >> +} > >> + > >> +static const struct component_master_ops virtio_rpmsg_cmp_ops = { > >> + .bind = virtio_rpmsg_bind, > >> + .unbind = virtio_rpmsg_unbind, > >> +}; > >> + > >> static int rpmsg_probe(struct virtio_device *vdev) > >> { > >> vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done }; > >> @@ -892,6 +942,7 @@ static int rpmsg_probe(struct virtio_device *vdev) > >> /* if supported by the remote processor, enable the name service */ > >> if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) { > >> vch = kzalloc(sizeof(*vch), GFP_KERNEL); > >> + > >> if (!vch) { > >> err = -ENOMEM; > >> goto free_coherent; > >> @@ -911,6 +962,20 @@ static int rpmsg_probe(struct virtio_device *vdev) > >> err = rpmsg_ns_register_device(rpdev_ns); > >> if (err) > >> goto free_coherent; > >> + /* register a component associated to the virtio platform */ > >> + component_match_add_release(&vdev->dev, &vrp->match, > >> + NULL, virtio_rpmsg_compare, > >> + &rpdev_ns->dev); > >> + > >> + vrp->bind_status = -ENXIO; > >> + init_completion(&vrp->completed); > >> + err = component_master_add_with_match(&vdev->dev, > >> + &virtio_rpmsg_cmp_ops, > >> + vrp->match); > >> + if (err) { > >> + dev_err(&vdev->dev, "failed to bind virtio rpmsg\n"); > >> + goto free_coherent; > >> + } > >> } > >> > >> /* > >> -- > >> 2.17.1 > >> > >> > >> > >>