From patchwork Fri Jun 18 07:52:43 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stephan Gerhold X-Patchwork-Id: 12330499 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7CBBC48BE8 for ; Fri, 18 Jun 2021 07:54:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EF4E6120A for ; Fri, 18 Jun 2021 07:54:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233615AbhFRH4c (ORCPT ); Fri, 18 Jun 2021 03:56:32 -0400 Received: from mo4-p02-ob.smtp.rzone.de ([85.215.255.84]:21257 "EHLO mo4-p02-ob.smtp.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232144AbhFRH4Z (ORCPT ); Fri, 18 Jun 2021 03:56:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; t=1624002850; s=strato-dkim-0002; d=gerhold.net; h=References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From:Cc:Date: From:Subject:Sender; bh=z+tAClt3iEH1Y1lZouLkiEl+3iFFlaNNiORG1MPID6Q=; b=UyHyVPziVyUnE8BJalQa6x2F28zN0U+4VkVHBKBBX0i+obgvIJL261q5Lu9OrjlldL ujD6FSr1upLeSteYWDxqU1cbfuYH/Mae/BnNIU+2Ui3iFtOu6Wc6fwSk6qc+DaTitde6 PQN68ngkMUttxqqgNbu2cAGw2pjZfuaBdnG0EagGw8zgPasDeTbARXr6lZ90GBe+Q4DE t8XDnfocSb/4uNdRZ4Lr2EzPw7dLyyGx+L/rN+bgq1Vv3ByvJp3SvAE3aVBz8A4L/vmN yacX9AE0uU18l4lqjXBhss7I3M5Mcou8NEaZjBgyPg/9FtuRzxSvoyW2BqcUqIXFC0Vh tUkQ== Authentication-Results: strato.com; dkim=none X-RZG-AUTH: ":P3gBZUipdd93FF5ZZvYFPugejmSTVR2nRPhVORvLd4SsytBXS7IYBkLahKxA626EOg==" X-RZG-CLASS-ID: mo00 Received: from droid.. by smtp.strato.de (RZmta 47.27.3 DYNA|AUTH) with ESMTPSA id 000885x5I7s94DF (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits)) (Client did not present a certificate); Fri, 18 Jun 2021 09:54:09 +0200 (CEST) From: Stephan Gerhold To: "David S. Miller" , Jakub Kicinski Cc: Loic Poulain , Bjorn Andersson , Aleksander Morgado , Sergey Ryazanov , Johannes Berg , Leon Romanovsky , M Chetan Kumar , linuxwwan@intel.com, Ohad Ben-Cohen , Mathieu Poirier , netdev@vger.kernel.org, linux-remoteproc@vger.kernel.org, linux-arm-msm@vger.kernel.org, phone-devel@vger.kernel.org, linux-kernel@vger.kernel.org, ~postmarketos/upstreaming@lists.sr.ht, Stephan Gerhold Subject: [PATCH net-next v2 3/3] net: wwan: Allow WWAN drivers to provide blocking tx and poll function Date: Fri, 18 Jun 2021 09:52:43 +0200 Message-Id: <20210618075243.42046-4-stephan@gerhold.net> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210618075243.42046-1-stephan@gerhold.net> References: <20210618075243.42046-1-stephan@gerhold.net> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org At the moment, the WWAN core provides wwan_port_txon/off() to implement blocking writes. The tx() port operation should not block, instead wwan_port_txon/off() should be called when the TX queue is full or has free space again. However, in some cases it is not straightforward to make use of that functionality. For example, the RPMSG API used by rpmsg_wwan_ctrl.c does not provide any way to be notified when the TX queue has space again. Instead, it only provides the following operations: - rpmsg_send(): blocking write (wait until there is space) - rpmsg_trysend(): non-blocking write (return error if no space) - rpmsg_poll(): set poll flags depending on TX queue state Generally that's totally sufficient for implementing a char device, but it does not fit well to the currently provided WWAN port ops. Most of the time, using the non-blocking rpmsg_trysend() in the WWAN tx() port operation works just fine. However, with high-frequent writes to the char device it is possible to trigger a situation where this causes issues. For example, consider the following (somewhat unrealistic) example: # dd if=/dev/zero bs=1000 of=/dev/wwan0p2QMI dd: error writing '/dev/wwan0p2QMI': Resource temporarily unavailable 1+0 records out This fails immediately after writing the first record. It's likely only a matter of time until this triggers issues for some real application (e.g. ModemManager sending a lot of large QMI packets). The rpmsg_char device does not have this problem, because it uses rpmsg_trysend() and rpmsg_poll() to support non-blocking operations. Make it possible to use the same in the RPMSG WWAN driver by extending the tx() operation with a "nonblock" parameter and adding an optional tx_poll() callback. This integrates nicely with the RPMSG API and does not break other WWAN drivers. With these changes, the dd example above blocks instead of exiting with an error. Cc: Loic Poulain Signed-off-by: Stephan Gerhold --- Changes in v2: - Fix EPOLLOUT being always set even if poll op is defined - Rename poll() op -> tx_poll() since it should be only used for TX --- Notes from v1: Note that rpmsg_poll() is an optional callback currently only implemented by the qcom_smd RPMSG provider. However, it should be easy to implement this for other RPMSG providers when needed. Another potential solution suggested by Loic Poulain in [1] is to always use the blocking rpmsg_send() from a workqueue/kthread and disable TX until it is done. I think this could also work (perhaps a bit more difficult to implement) but the main disadvantage is that I don't see a way to return any kind of error to the client with this approach. I assume we return immediately from the write() to the char device after scheduling the rpmsg_send(), so we already reported success when rpmsg_send() returns. At the end all that matters to me is that it works properly, so I'm open for any other suggestions. :) [1]: https://lore.kernel.org/linux-arm-msm/CAMZdPi_-Qa=JnThHs_h-144dAfSAjF5s+QdBawdXZ3kk8Mx8ng@mail.gmail.com/ --- drivers/net/wwan/iosm/iosm_ipc_port.c | 3 ++- drivers/net/wwan/mhi_wwan_ctrl.c | 3 ++- drivers/net/wwan/rpmsg_wwan_ctrl.c | 17 +++++++++++++++-- drivers/net/wwan/wwan_core.c | 11 +++++++---- drivers/net/wwan/wwan_hwsim.c | 3 ++- include/linux/wwan.h | 13 +++++++++---- 6 files changed, 37 insertions(+), 13 deletions(-) diff --git a/drivers/net/wwan/iosm/iosm_ipc_port.c b/drivers/net/wwan/iosm/iosm_ipc_port.c index beb944847398..2f874e41ceff 100644 --- a/drivers/net/wwan/iosm/iosm_ipc_port.c +++ b/drivers/net/wwan/iosm/iosm_ipc_port.c @@ -31,7 +31,8 @@ static void ipc_port_ctrl_stop(struct wwan_port *port) } /* transfer control data to modem */ -static int ipc_port_ctrl_tx(struct wwan_port *port, struct sk_buff *skb) +static int ipc_port_ctrl_tx(struct wwan_port *port, struct sk_buff *skb, + bool nonblock) { struct iosm_cdev *ipc_port = wwan_port_get_drvdata(port); diff --git a/drivers/net/wwan/mhi_wwan_ctrl.c b/drivers/net/wwan/mhi_wwan_ctrl.c index 1bc6b69aa530..9754f014d348 100644 --- a/drivers/net/wwan/mhi_wwan_ctrl.c +++ b/drivers/net/wwan/mhi_wwan_ctrl.c @@ -139,7 +139,8 @@ static void mhi_wwan_ctrl_stop(struct wwan_port *port) mhi_unprepare_from_transfer(mhiwwan->mhi_dev); } -static int mhi_wwan_ctrl_tx(struct wwan_port *port, struct sk_buff *skb) +static int mhi_wwan_ctrl_tx(struct wwan_port *port, struct sk_buff *skb, + bool nonblock) { struct mhi_wwan_dev *mhiwwan = wwan_port_get_drvdata(port); int ret; diff --git a/drivers/net/wwan/rpmsg_wwan_ctrl.c b/drivers/net/wwan/rpmsg_wwan_ctrl.c index de226cdb69fd..8d4cb48abcd8 100644 --- a/drivers/net/wwan/rpmsg_wwan_ctrl.c +++ b/drivers/net/wwan/rpmsg_wwan_ctrl.c @@ -54,12 +54,16 @@ static void rpmsg_wwan_ctrl_stop(struct wwan_port *port) rpwwan->ept = NULL; } -static int rpmsg_wwan_ctrl_tx(struct wwan_port *port, struct sk_buff *skb) +static int rpmsg_wwan_ctrl_tx(struct wwan_port *port, struct sk_buff *skb, + bool nonblock) { struct rpmsg_wwan_dev *rpwwan = wwan_port_get_drvdata(port); int ret; - ret = rpmsg_trysend(rpwwan->ept, skb->data, skb->len); + if (nonblock) + ret = rpmsg_trysend(rpwwan->ept, skb->data, skb->len); + else + ret = rpmsg_send(rpwwan->ept, skb->data, skb->len); if (ret) return ret; @@ -67,10 +71,19 @@ static int rpmsg_wwan_ctrl_tx(struct wwan_port *port, struct sk_buff *skb) return 0; } +static __poll_t rpmsg_wwan_ctrl_tx_poll(struct wwan_port *port, + struct file *filp, poll_table *wait) +{ + struct rpmsg_wwan_dev *rpwwan = wwan_port_get_drvdata(port); + + return rpmsg_poll(rpwwan->ept, filp, wait); +} + static const struct wwan_port_ops rpmsg_wwan_pops = { .start = rpmsg_wwan_ctrl_start, .stop = rpmsg_wwan_ctrl_stop, .tx = rpmsg_wwan_ctrl_tx, + .tx_poll = rpmsg_wwan_ctrl_tx_poll, }; static struct device *rpmsg_wwan_find_parent(struct device *dev) diff --git a/drivers/net/wwan/wwan_core.c b/drivers/net/wwan/wwan_core.c index 7e728042fc41..c0b124bd05cd 100644 --- a/drivers/net/wwan/wwan_core.c +++ b/drivers/net/wwan/wwan_core.c @@ -500,7 +500,8 @@ static void wwan_port_op_stop(struct wwan_port *port) mutex_unlock(&port->ops_lock); } -static int wwan_port_op_tx(struct wwan_port *port, struct sk_buff *skb) +static int wwan_port_op_tx(struct wwan_port *port, struct sk_buff *skb, + bool nonblock) { int ret; @@ -510,7 +511,7 @@ static int wwan_port_op_tx(struct wwan_port *port, struct sk_buff *skb) goto out_unlock; } - ret = port->ops->tx(port, skb); + ret = port->ops->tx(port, skb, nonblock); out_unlock: mutex_unlock(&port->ops_lock); @@ -637,7 +638,7 @@ static ssize_t wwan_port_fops_write(struct file *filp, const char __user *buf, return -EFAULT; } - ret = wwan_port_op_tx(port, skb); + ret = wwan_port_op_tx(port, skb, !!(filp->f_flags & O_NONBLOCK)); if (ret) { kfree_skb(skb); return ret; @@ -653,7 +654,9 @@ static __poll_t wwan_port_fops_poll(struct file *filp, poll_table *wait) poll_wait(filp, &port->waitqueue, wait); - if (!is_write_blocked(port)) + if (port->ops && port->ops->tx_poll) + mask |= port->ops->tx_poll(port, filp, wait); + else if (!is_write_blocked(port)) mask |= EPOLLOUT | EPOLLWRNORM; if (!is_read_blocked(port)) mask |= EPOLLIN | EPOLLRDNORM; diff --git a/drivers/net/wwan/wwan_hwsim.c b/drivers/net/wwan/wwan_hwsim.c index 472cae544a2b..e5ecbc70658d 100644 --- a/drivers/net/wwan/wwan_hwsim.c +++ b/drivers/net/wwan/wwan_hwsim.c @@ -83,7 +83,8 @@ static void wwan_hwsim_port_stop(struct wwan_port *wport) * * Be aware that this processor is not fully V.250 compliant. */ -static int wwan_hwsim_port_tx(struct wwan_port *wport, struct sk_buff *in) +static int wwan_hwsim_port_tx(struct wwan_port *wport, struct sk_buff *in, + bool nonblock) { struct wwan_hwsim_port *port = wwan_port_get_drvdata(wport); struct sk_buff *out; diff --git a/include/linux/wwan.h b/include/linux/wwan.h index 430a3a0817de..78cf98f088f4 100644 --- a/include/linux/wwan.h +++ b/include/linux/wwan.h @@ -6,6 +6,7 @@ #include #include +#include #include #include @@ -38,17 +39,21 @@ enum wwan_port_type { struct wwan_port; /** struct wwan_port_ops - The WWAN port operations - * @start: The routine for starting the WWAN port device. - * @stop: The routine for stopping the WWAN port device. + * @start: The routine for starting the WWAN port device. Required. + * @stop: The routine for stopping the WWAN port device. Required. * @tx: The routine that sends WWAN port protocol data to the device. + * May only block if nonblock is false. Required. + * @tx_poll: A routine to set additional TX poll flags. Optional. * * The wwan_port_ops structure contains a list of low-level operations - * that control a WWAN port device. All functions are mandatory. + * that control a WWAN port device. */ struct wwan_port_ops { int (*start)(struct wwan_port *port); void (*stop)(struct wwan_port *port); - int (*tx)(struct wwan_port *port, struct sk_buff *skb); + int (*tx)(struct wwan_port *port, struct sk_buff *skb, bool nonblock); + __poll_t (*tx_poll)(struct wwan_port *port, struct file *filp, + poll_table *wait); }; /**