From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 443C3C433F5 for ; Thu, 7 Oct 2021 10:20:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BA886113E for ; Thu, 7 Oct 2021 10:20:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232769AbhJGKWd (ORCPT ); Thu, 7 Oct 2021 06:22:33 -0400 Received: from mx08-00178001.pphosted.com ([91.207.212.93]:40944 "EHLO mx07-00178001.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S232166AbhJGKWc (ORCPT ); Thu, 7 Oct 2021 06:22:32 -0400 Received: from pps.filterd (m0046660.ppops.net [127.0.0.1]) by mx07-00178001.pphosted.com (8.16.1.2/8.16.1.2) with SMTP id 197ACunu005823; Thu, 7 Oct 2021 12:20:19 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=foss.st.com; h=from : subject : to : cc : references : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=selector1; bh=uxdP5tS3IB+aZZDmzrv/D7sDDw4iu+VGAibxcqFPt3c=; b=yTJUDkp6VqHjxT/hYXFyuYQvQpDfmAhQg0zgftet2aK5Y4JfTBDdhXhxC1GO5FjXppJQ ovgCG5SaiIiJY6UEVqZ9S+MVm4spdqeVvKgeuF5ykPpcFQajmsRvzmUJY5xaeV/HN7jW G9lp3T1mKToWFIJDDfGBAOurUGJGi2N3ulTtoz3JXwiNs+NlpHfx5NVohsht85ahT+Gc Dt6xPfex+3Os6uEQlHOH/S6Olz9diIMNmKrQQ1XwJAfs8iXoHU8EMK1J2LbXfUx+9I4/ vrcTOwCu+fJa9RqbNFCvIG2qwr1dVSMgmuZSReiaLvHxE3P9LbUasB7urNXlGvdluLQD VQ== Received: from beta.dmz-eu.st.com (beta.dmz-eu.st.com [164.129.1.35]) by mx07-00178001.pphosted.com with ESMTP id 3bhxwxg1m6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 07 Oct 2021 12:20:19 +0200 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id CF8A0100039; Thu, 7 Oct 2021 12:20:17 +0200 (CEST) Received: from Webmail-eu.st.com (sfhdag2node2.st.com [10.75.127.5]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 4B6BE21CA9A; Thu, 7 Oct 2021 12:20:17 +0200 (CEST) Received: from lmecxl0889.lme.st.com (10.75.127.47) by SFHDAG2NODE2.st.com (10.75.127.5) with Microsoft SMTP Server (TLS) id 15.0.1497.18; Thu, 7 Oct 2021 12:20:14 +0200 From: Arnaud POULIQUEN Subject: Re: [PATCH v8 2/2] tty: add rpmsg driver To: Bjorn Andersson CC: Ohad Ben-Cohen , Jonathan Corbet , Mathieu Poirier , Greg Kroah-Hartman , Jiri Slaby , Suman Anna , , , , References: <20210930160520.19678-1-arnaud.pouliquen@foss.st.com> <20210930160520.19678-3-arnaud.pouliquen@foss.st.com> <04f62e46-74ca-b7b5-a229-fdf6651343be@foss.st.com> Message-ID: Date: Thu, 7 Oct 2021 12:20:14 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.47] X-ClientProxiedBy: SFHDAG2NODE2.st.com (10.75.127.5) To SFHDAG2NODE2.st.com (10.75.127.5) X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.391,FMLib:17.0.607.475 definitions=2021-10-07_01,2021-10-07_01,2020-04-07_01 Precedence: bulk List-ID: X-Mailing-List: linux-remoteproc@vger.kernel.org Hello Bjorn, On 10/5/21 6:24 PM, Bjorn Andersson wrote: > On Tue 05 Oct 09:00 PDT 2021, Arnaud POULIQUEN wrote: > >> Hello Bjorn, >> >> On 10/4/21 10:12 PM, Bjorn Andersson wrote: >>> On Thu 30 Sep 09:05 PDT 2021, Arnaud Pouliquen wrote: >>> >>>> This driver exposes a standard TTY interface on top of the rpmsg >>>> framework through a rpmsg service. >>>> >>>> This driver supports multi-instances, offering a /dev/ttyRPMSGx entry >>>> per rpmsg endpoint. >>>> >>> >>> I think this looks pretty good, but it's a while since we discussed >>> this, reading your patches again makes me wonder: >> >> That's fair, the last discussion on the topic was over a year ago. >> >>> >>> 1) With all the efforts related to virtualization and adding things such >>> as I2C support there, what are the merits of putting a tty driver ontop >>> of rpmsg in comparison with directly on virtio - which would be used for >>> virtualization as well. >> >> As mentionned in the cover letter, the main advantage of the RPMsg vs virtio is >> that RPMsg is able to mix the services on an unique virtio instance. Using >> Virtio console implies to add a new virtio instance for each service (or >> instance of a service) with associated mailbox channels. >> Taking advantage of the RPMsg service mixing is important for platform (such as >> stm32MP1) on which coprocessor is limited in term of memory mapping. >> > > The limitations related to mapping additional virtio pipes does seem > like a reasonable one. I just hope we don't end up duplicating much of > the virtualization effort, with the recently concluded I2C client > support coming to mind. Difficult to have a prediction on this. This is something that should be coming with rational.The I2C management would be a good example. If we consider a I2C bus managed by the coprocessor. A main processor can have to access to a device on this bus. Is limited number of access to the device justify to reserve a dedicated memory area and a mailbox channel just for few device configurations on runtime? Anyway supported more virtio services in remoteproc and OpenAMP library seems something like a good middle term objective. The work I started around remoteproc virtio, I guess, is going in this direction. > >> I also expect that this service would be available for some other backend than >> the virtio one. >> > > Last time we discussed this I believe I mentioned the AT command > channels found in Qualcomm modems. Since then that got pushed into > drivers/net/wwan, for the few other cases rpmsg_char works fine. > >>> >>> 2) What prevents you from pointing your userspace tool at an rpmsg_char >>> endpoint? >> >> You are right rpmsg_char could be an alternative. But advantage of the TTY is: >> >> - It possible to reuse existing applications/tools relying on TTY devices. >> An example is a TTY RPMSG device dedicated for coprocessor traces that can be >> simply redirect to a log file or mixed to the kernel logs by scripts. >> Another exemple is the ability to ease migration from a 2-processors system >> solution (with UART-based IPC) to a system solution with an internal >> coprocessor. We received such requirement from some ST customers. >> > > I presume the transport itself provided by rpmsg_char would work just > fine for this, but that these applications expects something from the > tty framework, with its known ioctls etc? The rts mechanism i implemented in previous version is also something interesting to add on for the flow control. > >> - For rpmsg_char you have to share device between TX and RX (only one fopen >> allowed per device), while TTY allows you to manage one device in 2 independent >> threads/appliaction. >> > > At least in the Qualcomm case, where the channels have a state and > clients opening and closing the rpmsg_char will affect that state it > simplifies things a lot not to support a multi-client model. So I think > there's merit to this difference. > >> - TTY framework manages intermediate buffer that allow to free Rx RPMsg buffers. >> > > rpmsg_char does the same thing, by putting incoming messages on > epddev->queue. That's right, I forgot that, thanks for pointing it out. > >> So rpmsg_char and rpmsg_tty don't seem to me to cover exactly the same requierement. >> > > No, you're right there's some differences here. So can I consider that there is no blocking point on your side to move forward with this Rpmsg service? Thanks, Arnaud > > Regards, > Bjorn > >> Thanks, >> Arnaud >> >>> >>> Thanks, >>> Bjorn >>> >>>> Signed-off-by: Arnaud Pouliquen >>>> --- >>>> Documentation/serial/tty_rpmsg.rst | 15 ++ >>>> drivers/tty/Kconfig | 9 + >>>> drivers/tty/Makefile | 1 + >>>> drivers/tty/rpmsg_tty.c | 275 +++++++++++++++++++++++++++++ >>>> 4 files changed, 300 insertions(+) >>>> create mode 100644 Documentation/serial/tty_rpmsg.rst >>>> create mode 100644 drivers/tty/rpmsg_tty.c >>>> >>>> diff --git a/Documentation/serial/tty_rpmsg.rst b/Documentation/serial/tty_rpmsg.rst >>>> new file mode 100644 >>>> index 000000000000..b055107866c9 >>>> --- /dev/null >>>> +++ b/Documentation/serial/tty_rpmsg.rst >>>> @@ -0,0 +1,15 @@ >>>> +.. SPDX-License-Identifier: GPL-2.0 >>>> + >>>> +========= >>>> +RPMsg TTY >>>> +========= >>>> + >>>> +The rpmsg tty driver implements serial communication on the RPMsg bus to makes possible for >>>> +user-space programs to send and receive rpmsg messages as a standard tty protocol. >>>> + >>>> +The remote processor can instantiate a new tty by requesting a "rpmsg-tty" RPMsg service. >>>> + >>>> +The "rpmsg-tty" service is directly used for data exchange. No flow control is implemented. >>>> + >>>> +Information related to the RPMsg and associated tty device is available in >>>> +/sys/bus/rpmsg/devices/. >>>> diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig >>>> index 23cc988c68a4..5095513029d7 100644 >>>> --- a/drivers/tty/Kconfig >>>> +++ b/drivers/tty/Kconfig >>>> @@ -368,6 +368,15 @@ config VCC >>>> >>>> source "drivers/tty/hvc/Kconfig" >>>> >>>> +config RPMSG_TTY >>>> + tristate "RPMSG tty driver" >>>> + depends on RPMSG >>>> + help >>>> + Say y here to export rpmsg endpoints as tty devices, usually found >>>> + in /dev/ttyRPMSGx. >>>> + This makes it possible for user-space programs to send and receive >>>> + rpmsg messages as a standard tty protocol. >>>> + >>>> endif # TTY >>>> >>>> source "drivers/tty/serdev/Kconfig" >>>> diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile >>>> index a2bd75fbaaa4..07aca5184a55 100644 >>>> --- a/drivers/tty/Makefile >>>> +++ b/drivers/tty/Makefile >>>> @@ -26,5 +26,6 @@ obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o >>>> obj-$(CONFIG_GOLDFISH_TTY) += goldfish.o >>>> obj-$(CONFIG_MIPS_EJTAG_FDC_TTY) += mips_ejtag_fdc.o >>>> obj-$(CONFIG_VCC) += vcc.o >>>> +obj-$(CONFIG_RPMSG_TTY) += rpmsg_tty.o >>>> >>>> obj-y += ipwireless/ >>>> diff --git a/drivers/tty/rpmsg_tty.c b/drivers/tty/rpmsg_tty.c >>>> new file mode 100644 >>>> index 000000000000..0c99f54c2911 >>>> --- /dev/null >>>> +++ b/drivers/tty/rpmsg_tty.c >>>> @@ -0,0 +1,275 @@ >>>> +// SPDX-License-Identifier: GPL-2.0 >>>> +/* >>>> + * Copyright (C) STMicroelectronics 2021 - All Rights Reserved >>>> + */ >>>> + >>>> +#include >>>> +#include >>>> +#include >>>> +#include >>>> +#include >>>> + >>>> +#define MAX_TTY_RPMSG 32 >>>> + >>>> +static DEFINE_IDR(tty_idr); /* tty instance id */ >>>> +static DEFINE_MUTEX(idr_lock); /* protects tty_idr */ >>>> + >>>> +static struct tty_driver *rpmsg_tty_driver; >>>> + >>>> +struct rpmsg_tty_port { >>>> + struct tty_port port; /* TTY port data */ >>>> + int id; /* TTY rpmsg index */ >>>> + struct rpmsg_device *rpdev; /* rpmsg device */ >>>> +}; >>>> + >>>> +static int rpmsg_tty_cb(struct rpmsg_device *rpdev, void *data, int len, void *priv, u32 src) >>>> +{ >>>> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev); >>>> + int copied; >>>> + >>>> + if (!len) >>>> + return -EINVAL; >>>> + copied = tty_insert_flip_string(&cport->port, data, len); >>>> + if (copied != len) >>>> + dev_dbg(&rpdev->dev, "Trunc buffer: available space is %d\n", >>>> + copied); >>>> + tty_flip_buffer_push(&cport->port); >>>> + >>>> + return 0; >>>> +} >>>> + >>>> +static int rpmsg_tty_install(struct tty_driver *driver, struct tty_struct *tty) >>>> +{ >>>> + struct rpmsg_tty_port *cport = idr_find(&tty_idr, tty->index); >>>> + >>>> + if (!cport) { >>>> + dev_err(tty->dev, "Cannot get cport\n"); >>>> + return -ENODEV; >>>> + } >>>> + >>>> + tty->driver_data = cport; >>>> + >>>> + return tty_port_install(&cport->port, driver, tty); >>>> +} >>>> + >>>> +static int rpmsg_tty_open(struct tty_struct *tty, struct file *filp) >>>> +{ >>>> + return tty_port_open(tty->port, tty, filp); >>>> +} >>>> + >>>> +static void rpmsg_tty_close(struct tty_struct *tty, struct file *filp) >>>> +{ >>>> + return tty_port_close(tty->port, tty, filp); >>>> +} >>>> + >>>> +static int rpmsg_tty_write(struct tty_struct *tty, const u8 *buf, int len) >>>> +{ >>>> + struct rpmsg_tty_port *cport = tty->driver_data; >>>> + struct rpmsg_device *rpdev; >>>> + int msg_max_size, msg_size; >>>> + int ret; >>>> + >>>> + rpdev = cport->rpdev; >>>> + >>>> + dev_dbg(&rpdev->dev, "Send msg from tty->index = %d, len = %d\n", tty->index, len); >>>> + >>>> + msg_max_size = rpmsg_get_mtu(rpdev->ept); >>>> + if (msg_max_size < 0) >>>> + return msg_max_size; >>>> + >>>> + msg_size = min(len, msg_max_size); >>>> + >>>> + /* >>>> + * Use rpmsg_trysend instead of rpmsg_send to send the message so the caller is not >>>> + * hung until a rpmsg buffer is available. In such case rpmsg_trysend returns -ENOMEM. >>>> + */ >>>> + ret = rpmsg_trysend(rpdev->ept, (void *)buf, msg_size); >>>> + if (ret) { >>>> + dev_dbg(&rpdev->dev, "rpmsg_send failed: %d\n", ret); >>>> + return ret; >>>> + } >>>> + >>>> + return msg_size; >>>> +} >>>> + >>>> +static unsigned int rpmsg_tty_write_room(struct tty_struct *tty) >>>> +{ >>>> + struct rpmsg_tty_port *cport = tty->driver_data; >>>> + int size; >>>> + >>>> + size = rpmsg_get_mtu(cport->rpdev->ept); >>>> + if (size < 0) >>>> + return 0; >>>> + >>>> + return size; >>>> +} >>>> + >>>> +static const struct tty_operations rpmsg_tty_ops = { >>>> + .install = rpmsg_tty_install, >>>> + .open = rpmsg_tty_open, >>>> + .close = rpmsg_tty_close, >>>> + .write = rpmsg_tty_write, >>>> + .write_room = rpmsg_tty_write_room, >>>> +}; >>>> + >>>> +static struct rpmsg_tty_port *rpmsg_tty_alloc_cport(void) >>>> +{ >>>> + struct rpmsg_tty_port *cport; >>>> + int err; >>>> + >>>> + cport = kzalloc(sizeof(*cport), GFP_KERNEL); >>>> + if (!cport) >>>> + return ERR_PTR(-ENOMEM); >>>> + >>>> + mutex_lock(&idr_lock); >>>> + cport->id = idr_alloc(&tty_idr, cport, 0, MAX_TTY_RPMSG, GFP_KERNEL); >>>> + mutex_unlock(&idr_lock); >>>> + >>>> + if (cport->id < 0) { >>>> + err = cport->id; >>>> + kfree(cport); >>>> + return ERR_PTR(err); >>>> + } >>>> + >>>> + return cport; >>>> +} >>>> + >>>> +static void rpmsg_tty_release_cport(struct rpmsg_tty_port *cport) >>>> +{ >>>> + mutex_lock(&idr_lock); >>>> + idr_remove(&tty_idr, cport->id); >>>> + mutex_unlock(&idr_lock); >>>> + >>>> + kfree(cport); >>>> +} >>>> + >>>> +static const struct tty_port_operations rpmsg_tty_port_ops = { }; >>>> + >>>> +static int rpmsg_tty_probe(struct rpmsg_device *rpdev) >>>> +{ >>>> + struct rpmsg_tty_port *cport; >>>> + struct device *dev = &rpdev->dev; >>>> + struct device *tty_dev; >>>> + int ret; >>>> + >>>> + cport = rpmsg_tty_alloc_cport(); >>>> + if (IS_ERR(cport)) { >>>> + dev_err(dev, "Failed to alloc tty port\n"); >>>> + return PTR_ERR(cport); >>>> + } >>>> + >>>> + tty_port_init(&cport->port); >>>> + cport->port.ops = &rpmsg_tty_port_ops; >>>> + >>>> + tty_dev = tty_port_register_device(&cport->port, rpmsg_tty_driver, >>>> + cport->id, dev); >>>> + if (IS_ERR(tty_dev)) { >>>> + dev_err(dev, "Failed to register tty port\n"); >>>> + ret = PTR_ERR(tty_dev); >>>> + goto err_destroy; >>>> + } >>>> + >>>> + cport->rpdev = rpdev; >>>> + >>>> + dev_set_drvdata(dev, cport); >>>> + >>>> + dev_dbg(dev, "New channel: 0x%x -> 0x%x : ttyRPMSG%d\n", >>>> + rpdev->src, rpdev->dst, cport->id); >>>> + >>>> + return 0; >>>> + >>>> +err_destroy: >>>> + tty_port_destroy(&cport->port); >>>> + rpmsg_tty_release_cport(cport); >>>> + >>>> + return ret; >>>> +} >>>> + >>>> +static void rpmsg_tty_remove(struct rpmsg_device *rpdev) >>>> +{ >>>> + struct rpmsg_tty_port *cport = dev_get_drvdata(&rpdev->dev); >>>> + >>>> + dev_dbg(&rpdev->dev, "Removing rpmsg tty device %d\n", cport->id); >>>> + >>>> + /* User hang up to release the tty */ >>>> + if (tty_port_initialized(&cport->port)) >>>> + tty_port_tty_hangup(&cport->port, false); >>>> + >>>> + tty_unregister_device(rpmsg_tty_driver, cport->id); >>>> + >>>> + tty_port_destroy(&cport->port); >>>> + rpmsg_tty_release_cport(cport); >>>> +} >>>> + >>>> +static struct rpmsg_device_id rpmsg_driver_tty_id_table[] = { >>>> + { .name = "rpmsg-tty" }, >>>> + { }, >>>> +}; >>>> +MODULE_DEVICE_TABLE(rpmsg, rpmsg_driver_tty_id_table); >>>> + >>>> +static struct rpmsg_driver rpmsg_tty_rpmsg_drv = { >>>> + .drv.name = KBUILD_MODNAME, >>>> + .id_table = rpmsg_driver_tty_id_table, >>>> + .probe = rpmsg_tty_probe, >>>> + .callback = rpmsg_tty_cb, >>>> + .remove = rpmsg_tty_remove, >>>> +}; >>>> + >>>> +static int __init rpmsg_tty_init(void) >>>> +{ >>>> + int err; >>>> + >>>> + rpmsg_tty_driver = tty_alloc_driver(MAX_TTY_RPMSG, TTY_DRIVER_REAL_RAW | >>>> + TTY_DRIVER_DYNAMIC_DEV); >>>> + if (IS_ERR(rpmsg_tty_driver)) >>>> + return PTR_ERR(rpmsg_tty_driver); >>>> + >>>> + rpmsg_tty_driver->driver_name = "rpmsg_tty"; >>>> + rpmsg_tty_driver->name = "ttyRPMSG"; >>>> + rpmsg_tty_driver->major = 0; >>>> + rpmsg_tty_driver->type = TTY_DRIVER_TYPE_CONSOLE; >>>> + >>>> + /* Disable unused mode by default */ >>>> + rpmsg_tty_driver->init_termios = tty_std_termios; >>>> + rpmsg_tty_driver->init_termios.c_lflag &= ~(ECHO | ICANON); >>>> + rpmsg_tty_driver->init_termios.c_oflag &= ~(OPOST | ONLCR); >>>> + >>>> + tty_set_operations(rpmsg_tty_driver, &rpmsg_tty_ops); >>>> + >>>> + err = tty_register_driver(rpmsg_tty_driver); >>>> + if (err < 0) { >>>> + pr_err("Couldn't install rpmsg tty driver: err %d\n", err); >>>> + goto error_put; >>>> + } >>>> + >>>> + err = register_rpmsg_driver(&rpmsg_tty_rpmsg_drv); >>>> + if (err < 0) { >>>> + pr_err("Couldn't register rpmsg tty driver: err %d\n", err); >>>> + goto error_unregister; >>>> + } >>>> + >>>> + return 0; >>>> + >>>> +error_unregister: >>>> + tty_unregister_driver(rpmsg_tty_driver); >>>> + >>>> +error_put: >>>> + tty_driver_kref_put(rpmsg_tty_driver); >>>> + >>>> + return err; >>>> +} >>>> + >>>> +static void __exit rpmsg_tty_exit(void) >>>> +{ >>>> + unregister_rpmsg_driver(&rpmsg_tty_rpmsg_drv); >>>> + tty_unregister_driver(rpmsg_tty_driver); >>>> + tty_driver_kref_put(rpmsg_tty_driver); >>>> + idr_destroy(&tty_idr); >>>> +} >>>> + >>>> +module_init(rpmsg_tty_init); >>>> +module_exit(rpmsg_tty_exit); >>>> + >>>> +MODULE_AUTHOR("Arnaud Pouliquen "); >>>> +MODULE_DESCRIPTION("remote processor messaging tty driver"); >>>> +MODULE_LICENSE("GPL v2"); >>>> -- >>>> 2.17.1 >>>>