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Wed, 05 Jul 2023 16:30:58 +0200 Date: Wed, 5 Jul 2023 16:30:57 +0200 From: Johan Hovold To: Pierre-Louis Bossart Cc: Johan Hovold , Mark Brown , Vinod Koul , Bard Liao , Sanyog Kale , Srinivas Kandagatla , Banajit Goswami , Liam Girdwood , Jaroslav Kysela , Takashi Iwai , alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Rander Wang Subject: Re: [PATCH 1/8] soundwire: fix enumeration completion Message-ID: References: <20230705123018.30903-1-johan+linaro@kernel.org> <20230705123018.30903-2-johan+linaro@kernel.org> <907ad7a3-3384-c0c4-90a9-5beab4cc45e0@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <907ad7a3-3384-c0c4-90a9-5beab4cc45e0@linux.intel.com> Message-ID-Hash: QDFRGYYN5UYAWXBZTXLBGRZGKOKRV3OD X-Message-ID-Hash: QDFRGYYN5UYAWXBZTXLBGRZGKOKRV3OD X-MailFrom: johan@kernel.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-alsa-devel.alsa-project.org-0; header-match-alsa-devel.alsa-project.org-1; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Wed, Jul 05, 2023 at 02:53:17PM +0200, Pierre-Louis Bossart wrote: > On 7/5/23 14:30, Johan Hovold wrote: > > The soundwire subsystem uses two completion structures that allow > > drivers to wait for soundwire device to become enumerated on the bus and > > initialised by their drivers, respectively. > > > > The code implementing the signalling is currently broken as it does not > > signal all current and future waiters and also uses the wrong > > reinitialisation function, which can potentially lead to memory > > corruption if there are still waiters on the queue. > > That change sounds good, but I am not following the two paragraphs below. > > > Not signalling future waiters specifically breaks sound card probe > > deferrals as codec drivers can not tell that the soundwire device is > > already attached when being reprobed. > > What makes you say that? There is a test in the probe and the codec > driver will absolutely be notified, see bus_type.c > > if (drv->ops && drv->ops->update_status) { > ret = drv->ops->update_status(slave, slave->status); > if (ret < 0) > dev_warn(dev, "%s: update_status failed with status %d\n", __func__, > ret); > } I'm talking about signalling the codec driver using the soundwire device via the completion structs. Unless the underling device is detached and reattached, trying to wait for completion a second time will currently timeout instead of returning immediately. This affects codecs like rt5682, which wait for completion in component probe (see rt5682_probe()). > > Some codec runtime PM > > implementations suffer from similar problems as waiting for enumeration > > during resume can also timeout despite the device already having been > > enumerated. > > I am not following this either. Are you saying the wait_for_completion() > times out because of the init_completion/reinit_completion confusion, or > something else. It times out because the completion counter is not saturated unless you use complete_all(). Drivers that wait unconditionally in resume, will time out the second time they are runtime resumed unless the underlying device has been detached and reattached in the meantime (e.g. wsa881x_runtime_resume()). Johan