From patchwork Tue Jul 14 12:48:04 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11662813 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9036B913 for ; Tue, 14 Jul 2020 12:49:42 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6964E2242C for ; Tue, 14 Jul 2020 12:49:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="2KOkQheG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6964E2242C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=baikalelectronics.ru Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To:Message-ID:Date: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=lIt6AiPiHKFr+EQ7vtCmmejy6sjGVH1PSct/clrP7kE=; b=2KOkQheG/mLvmd2GsDPW4jwZi WAgmT1I5lvmHOSL5QeULZXMW8vakbdJd7UxY/zpW+bT5JCfq8gAYeAR5PnKaqGxmvtiLUbHga6W6H g6xfR5TJoZv7zb2mlf45NJKTJEtxtw0H2KzDtNEXj1308P+zHbRax+Ev0pEasB17gXdWDhSAXKwwg oyOt/6JSfyXEtNuIdWgPfF1JhQOsSAKqYb0ZdatQBRpX5VpPxBqMdxEcLRIpw4R0CRyWqdwlVCU0w dl31/JPAAvEl5Sf7c/Ljz2vAiETzFr2oiIQXQgWFF2CrZvVnse3onDUPsyBZDpmA4tmkaolcbBPdO SH/0j/MUw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jvKM5-0005pV-Qp; Tue, 14 Jul 2020 12:48:17 +0000 Received: from mx.chip.baikal.ru ([94.125.187.42] helo=mail.baikalelectronics.ru) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jvKM1-0005n0-0e for linux-arm-kernel@lists.infradead.org; Tue, 14 Jul 2020 12:48:14 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 4D24F8030809; Tue, 14 Jul 2020 12:48:12 +0000 (UTC) X-Virus-Scanned: amavisd-new at baikalelectronics.ru Received: from mail.baikalelectronics.ru ([127.0.0.1]) by localhost (mail.baikalelectronics.ru [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id qVqk18cJToeC; Tue, 14 Jul 2020 15:48:11 +0300 (MSK) From: Serge Semin To: Greg Kroah-Hartman , Jiri Slaby Subject: [PATCH v8 1/4] serial: 8250: Add 8250 port clock update method Date: Tue, 14 Jul 2020 15:48:04 +0300 Message-ID: <20200714124808.21493-2-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200714124808.21493-1-Sergey.Semin@baikalelectronics.ru> References: <20200714124808.21493-1-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 X-ClientProxiedBy: MAIL.baikal.int (192.168.51.25) To mail (192.168.51.25) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200714_084813_452222_F36673C9 X-CRM114-Status: GOOD ( 14.46 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Maxime Ripard , Thomas Bogendoerfer , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, Russell King , Serge Semin , Alexey Malahov , Serge Semin , Pavel Parkhomenko , linux-serial@vger.kernel.org, Andy Shevchenko , Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org Some platforms can be designed in a way so the UART port reference clock might be asynchronously changed at some point. In Baikal-T1 SoC this may happen due to the reference clock being shared between two UART ports, on the Allwinner SoC the reference clock is derived from the CPU clock, so any CPU frequency change should get to be known/reflected by/in the UART controller as well. But it's not enough to just update the uart_port->uartclk field of the corresponding UART port, the 8250 controller reference clock divisor should be altered so to preserve current baud rate setting. All of these things is done in a coherent way by calling the serial8250_update_uartclk() method provided in this patch. Though note that it isn't supposed to be called from within the UART port callbacks because the locks using to the protect the UART port data are already taken in there. Signed-off-by: Serge Semin --- Changelog v4: - Export serial8250_update_uartclk() symbol for GPL modules only. Changelog v7: - Wake the device up on the serial port divider update. --- drivers/tty/serial/8250/8250_port.c | 40 +++++++++++++++++++++++++++++ include/linux/serial_8250.h | 2 ++ 2 files changed, 42 insertions(+) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 4d83c85a7389..7bfa0f7d9d60 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2628,6 +2628,46 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port, (port->uartclk + tolerance) / 16); } +/* + * Note in order to avoid the tty port mutex deadlock don't use the next method + * within the uart port callbacks. Primarily it's supposed to be utilized to + * handle a sudden reference clock rate change. + */ +void serial8250_update_uartclk(struct uart_port *port, unsigned int uartclk) +{ + struct uart_8250_port *up = up_to_u8250p(port); + unsigned int baud, quot, frac = 0; + struct ktermios *termios; + unsigned long flags; + + mutex_lock(&port->state->port.mutex); + + if (port->uartclk == uartclk) + goto out_lock; + + port->uartclk = uartclk; + termios = &port->state->port.tty->termios; + + baud = serial8250_get_baud_rate(port, termios, NULL); + quot = serial8250_get_divisor(port, baud, &frac); + + serial8250_rpm_get(up); + spin_lock_irqsave(&port->lock, flags); + + uart_update_timeout(port, termios->c_cflag, baud); + + serial8250_set_divisor(port, baud, quot, frac); + serial_port_out(port, UART_LCR, up->lcr); + serial8250_out_MCR(up, UART_MCR_DTR | UART_MCR_RTS); + + spin_unlock_irqrestore(&port->lock, flags); + serial8250_rpm_put(up); + +out_lock: + mutex_unlock(&port->state->port.mutex); +} +EXPORT_SYMBOL_GPL(serial8250_update_uartclk); + void serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old) diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h index 6545f8cfc8fa..2b70f736b091 100644 --- a/include/linux/serial_8250.h +++ b/include/linux/serial_8250.h @@ -155,6 +155,8 @@ extern int early_serial_setup(struct uart_port *port); extern int early_serial8250_setup(struct earlycon_device *device, const char *options); +extern void serial8250_update_uartclk(struct uart_port *port, + unsigned int uartclk); extern void serial8250_do_set_termios(struct uart_port *port, struct ktermios *termios, struct ktermios *old); extern void serial8250_do_set_ldisc(struct uart_port *port,