From patchwork Wed May 6 23:31:32 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11532033 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 9FFE514B4 for ; Wed, 6 May 2020 23:32:23 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 7D55A20735 for ; Wed, 6 May 2020 23:32:23 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="ijV+6v0g" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D55A20735 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-mediatek-bounces+patchwork-linux-mediatek=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.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=DpP7mruvRGK9TMfYzrF5w4mN/LdyB9tBbrXEzk/rpvc=; b=ijV+6v0gQcysE1 PZY+SfJV9OYl5e/ky92r5UHvJQDNLc7AG34Kz3tXcSdw5TVuDxc2P6xv2zUinBFxo+y9KxWY9NVy0 E4Nu6XRKkR8WZ5tOE0jaLC3qDkKUbmTC8gSBBAKPRSc66Q11SNDvY1qRwxC5uFiseQvr2pA6g5J5Q qi1N8fvdfHnTqozKeB8TO1VSk7pmDNOeg2v8ntOROFpikV+qrx+dBxGn625fQ8mV2iXaX9dVDK17Y thZyRaSf64oLDRPu7U6/i4L8DLm0EwcUeF32OGCh287qhQ3bTCxPLXkL68LwVWQlURhfeN/k5663+ yFPVimJ3/uvVZwLQtoig==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTWW-0002Xn-PO; Wed, 06 May 2020 23:32:20 +0000 Received: from mx.baikalelectronics.com ([94.125.187.42] helo=mail.baikalelectronics.ru) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTW7-00024n-C4; Wed, 06 May 2020 23:31:57 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 70B2C8030808; Wed, 6 May 2020 23:31:51 +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 MhBbxmp3w3vz; Thu, 7 May 2020 02:31:48 +0300 (MSK) From: Serge Semin To: Thomas Bogendoerfer , Greg Kroah-Hartman , Jiri Slaby , Long Cheng Subject: [PATCH v3 1/4] serial: 8250: Fix max baud limit in generic 8250 port Date: Thu, 7 May 2020 02:31:32 +0300 Message-ID: <20200506233136.11842-2-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200506233136.11842-1-Sergey.Semin@baikalelectronics.ru> References: <20200323024611.16039-1-Sergey.Semin@baikalelectronics.ru> <20200506233136.11842-1-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-20200506_163155_766990_F1298F16 X-CRM114-Status: GOOD ( 10.40 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.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 0.0 TVD_PH_BODY_ACCOUNTS_PRE The body matches phrases such as "accounts suspended", "account credited", "account verification" X-BeenThere: linux-mediatek@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 , Stefan Roese , linux-mips@vger.kernel.org, Paul Burton , Arnd Bergmann , Catalin Marinas , linux-kernel@vger.kernel.org, Russell King , Ralf Baechle , Alexey Malahov , Serge Semin , Mika Westerberg , Lukas Wunner , linux-mediatek@lists.infradead.org, Serge Semin , linux-serial@vger.kernel.org, Andy Shevchenko , Will Deacon , linux-arm-kernel@lists.infradead.org, Vignesh Raghavendra Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+patchwork-linux-mediatek=patchwork.kernel.org@lists.infradead.org Standard 8250 UART ports are designed in a way so they can communicate with baud rates up to 1/16 of a reference frequency. It's expected from most of the currently supported UART controllers. That's why the former version of serial8250_get_baud_rate() method called uart_get_baud_rate() with min and max baud rates passed as (port->uartclk / 16 / UART_DIV_MAX) and ((port->uartclk + tolerance) / 16) respectively. Doing otherwise, like it was suggested in commit ("serial: 8250_mtk: support big baud rate."), caused acceptance of bauds, which was higher than the normal UART controllers actually supported. As a result if some user-space program requested to set a baud greater than (uartclk / 16) it would have been permitted without truncation, but then serial8250_get_divisor(baud) (which calls uart_get_divisor() to get the reference clock divisor) would have returned a zero divisor. Setting zero divisor will cause an unpredictable effect varying from chip to chip. In case of DW APB UART the communications just stop. Lets fix this problem by getting back the limitation of (uartclk + tolerance) / 16 maximum baud supported by the generic 8250 port. Mediatek 8250 UART ports driver developer shouldn't have touched it in the first place notably seeing he already provided a custom version of set_termios() callback in that glue-driver which took into account the extended baud rate values and accordingly updated the standard and vendor-specific divisor latch registers anyway. Fixes: 81bb549fdf14 ("serial: 8250_mtk: support big baud rate.") Signed-off-by: Serge Semin Cc: Alexey Malahov Cc: Thomas Bogendoerfer Cc: Paul Burton Cc: Ralf Baechle Cc: Arnd Bergmann Cc: Long Cheng Cc: Andy Shevchenko Cc: Maxime Ripard Cc: Catalin Marinas Cc: Will Deacon Cc: Russell King Cc: linux-mips@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-mediatek@lists.infradead.org Reviewed-by: Andy Shevchenko --- drivers/tty/serial/8250/8250_port.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index f77bf820b7a3..4d83c85a7389 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2615,6 +2615,8 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port, struct ktermios *termios, struct ktermios *old) { + unsigned int tolerance = port->uartclk / 100; + /* * Ask the core to calculate the divisor for us. * Allow 1% tolerance at the upper limit so uart clks marginally @@ -2623,7 +2625,7 @@ static unsigned int serial8250_get_baud_rate(struct uart_port *port, */ return uart_get_baud_rate(port, termios, old, port->uartclk / 16 / UART_DIV_MAX, - port->uartclk); + (port->uartclk + tolerance) / 16); } void From patchwork Wed May 6 23:31:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11532035 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 321FB913 for ; Wed, 6 May 2020 23:32:24 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 100FA20735 for ; Wed, 6 May 2020 23:32:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="dz/Vgf2B" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 100FA20735 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-mediatek-bounces+patchwork-linux-mediatek=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.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=z9Tm6t4nG9Fkmbpxfxv6BaFZ7GZ/TOb5kTzr1FZ92OI=; b=dz/Vgf2B1k5v3/ 1SWkPSGjEb6jjr+sPkW5pVYQ6m5IH1AI8EJJ+jDW6KDhbVMZwMAAF425COQRyaV7LMTxlpXsJYi78 U74vjyAFz/DSfCTUrua3TtGtHVV+uhPjaNntsMRPAsOHApQZi8i5Iowgk0g5akpCozrDUmnDnCZ47 au/5EdAaTpBrXfXMOG7gjGQEMInwrGGP2TUpJdOo2TzzvLoo/DWKdY7PO2eTUk6xFiQthRYubkIO3 zynXFRixo3WU+6WL6TEZ+vA6uewXGUmpDJBay6jJfAY15AtrWLf79eCl3VK3P7tbmImv1ZjpiatBB ZibuxL7Yx1aShLFJcclw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTWY-0002Zo-HM; Wed, 06 May 2020 23:32:22 +0000 Received: from ns2.baikalelectronics.com ([94.125.187.42] helo=mail.baikalelectronics.ru) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTW7-00025B-CB; Wed, 06 May 2020 23:31:57 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 2DBD4803087B; Wed, 6 May 2020 23:31:53 +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 wQ_eRoPPIA7H; Thu, 7 May 2020 02:31:52 +0300 (MSK) From: Serge Semin To: Thomas Bogendoerfer , Greg Kroah-Hartman , Jiri Slaby Subject: [PATCH v3 2/4] serial: 8250: Add 8250 port clock update method Date: Thu, 7 May 2020 02:31:33 +0300 Message-ID: <20200506233136.11842-3-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200506233136.11842-1-Sergey.Semin@baikalelectronics.ru> References: <20200323024611.16039-1-Sergey.Semin@baikalelectronics.ru> <20200506233136.11842-1-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-20200506_163155_767469_1724E887 X-CRM114-Status: GOOD ( 13.05 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.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-mediatek@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Vignesh Raghavendra , Catalin Marinas , Dmitry Safonov <0x7f454c46@gmail.com>, Yegor Yefremov , Serge Semin , Stefan Roese , Will Deacon , Paul Burton , Russell King , Long Cheng , linux-arm-kernel@lists.infradead.org, linux-serial@vger.kernel.org, Arnd Bergmann , Maxime Ripard , Alexey Malahov , linux-mediatek@lists.infradead.org, Thomas Gleixner , Andy Shevchenko , Mika Westerberg , Allison Randal , linux-mips@vger.kernel.org, Ralf Baechle , linux-kernel@vger.kernel.org, Serge Semin , Lukas Wunner Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+patchwork-linux-mediatek=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 Cc: Alexey Malahov Cc: Thomas Bogendoerfer Cc: Paul Burton Cc: Ralf Baechle Cc: Arnd Bergmann Cc: Long Cheng Cc: Andy Shevchenko Cc: Maxime Ripard Cc: Catalin Marinas Cc: Will Deacon Cc: Russell King Cc: linux-mips@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-mediatek@lists.infradead.org --- drivers/tty/serial/8250/8250_port.c | 38 +++++++++++++++++++++++++++++ include/linux/serial_8250.h | 2 ++ 2 files changed, 40 insertions(+) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 4d83c85a7389..484ff9df1432 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -2628,6 +2628,44 @@ 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); + + 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); + +out_lock: + mutex_unlock(&port->state->port.mutex); +} +EXPORT_SYMBOL(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, From patchwork Wed May 6 23:31:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11532039 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 BC76E913 for ; Wed, 6 May 2020 23:32:58 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 9A88A20735 for ; 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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTX6-0003Ci-Ec; Wed, 06 May 2020 23:32:56 +0000 Received: from mx.baikalchip.com ([94.125.187.42] helo=mail.baikalelectronics.ru) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTW8-00026K-8T; Wed, 06 May 2020 23:31:58 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 9205D80307C2; Wed, 6 May 2020 23:31:55 +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 Cja-hvFMOdwU; Thu, 7 May 2020 02:31:54 +0300 (MSK) From: Serge Semin To: Thomas Bogendoerfer , Greg Kroah-Hartman , Jiri Slaby , Andy Shevchenko Subject: [PATCH v3 3/4] serial: 8250_dw: Simplify the ref clock rate setting procedure Date: Thu, 7 May 2020 02:31:34 +0300 Message-ID: <20200506233136.11842-4-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200506233136.11842-1-Sergey.Semin@baikalelectronics.ru> References: <20200323024611.16039-1-Sergey.Semin@baikalelectronics.ru> <20200506233136.11842-1-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-20200506_163156_477240_E8C0AD67 X-CRM114-Status: GOOD ( 11.35 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.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-mediatek@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 , Kefeng Wang , Heikki Krogerus , linux-kernel@vger.kernel.org, Paul Burton , Arnd Bergmann , Catalin Marinas , Russell King , Ralf Baechle , Alexey Malahov , Serge Semin , Long Cheng , linux-mediatek@lists.infradead.org, Serge Semin , linux-serial@vger.kernel.org, linux-mips@vger.kernel.org, Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+patchwork-linux-mediatek=patchwork.kernel.org@lists.infradead.org Really instead of twice checking the clk_round_rate() return value we could do it once, and if it isn't error the clock rate can be changed. By doing so we decrease a number of ret-value tests and remove a weird goto-based construction implemented in the dw8250_set_termios() method. Signed-off-by: Serge Semin Cc: Alexey Malahov Cc: Thomas Bogendoerfer Cc: Paul Burton Cc: Ralf Baechle Cc: Arnd Bergmann Cc: Long Cheng Cc: Andy Shevchenko Cc: Maxime Ripard Cc: Catalin Marinas Cc: Will Deacon Cc: Russell King Cc: linux-mips@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-mediatek@lists.infradead.org --- drivers/tty/serial/8250/8250_dw.c | 15 ++++----------- 1 file changed, 4 insertions(+), 11 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index aab3cccc6789..12866083731d 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -282,20 +282,13 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios, clk_disable_unprepare(d->clk); rate = clk_round_rate(d->clk, baud * 16); - if (rate < 0) - ret = rate; - else if (rate == 0) - ret = -ENOENT; - else + if (rate > 0) { ret = clk_set_rate(d->clk, rate); + if (!ret) + p->uartclk = rate; + } clk_prepare_enable(d->clk); - if (ret) - goto out; - - p->uartclk = rate; - -out: p->status &= ~UPSTAT_AUTOCTS; if (termios->c_cflag & CRTSCTS) p->status |= UPSTAT_AUTOCTS; From patchwork Wed May 6 23:31:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Serge Semin X-Patchwork-Id: 11532043 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 4C187913 for ; Wed, 6 May 2020 23:33:16 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 2A3D320735 for ; Wed, 6 May 2020 23:33:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="OfcrMkC5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2A3D320735 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-mediatek-bounces+patchwork-linux-mediatek=patchwork.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.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=uMtsz8+a4Pg/goWJYBQcVfSw5xaGKX6HmBXfsGa5khA=; b=OfcrMkC5HTeFQ7 WEguSLLOKChvQqOPdz5rtMLbrVl/bMknHS/ISPbBa0mdiEtmOF1rqqF3WJB2e4aRbsCZmxPt3Exai bG/ffzW2bxXI8UqXOfzKYu3rQbYq4z3uuOjQqAssaNg6AriIzxYHtlb4j/shwvLXjj8Hb22mxdqtR 6f5dBffiG1JsQUnFw9uWjVKYJd0J2t0tnzcXsn6T/2UT0rhvxz2dt1lPilmfKFAJHYNICMS4EQeMv yUGjVb0gqX/wCoyNGTzAdaUKNh7YuX4B1pQO25k37G/ygmbJNgb7qlVqq0uWrdS9Hq0ek0gFcM/EX ac+xtnJD/MJuy8yv7hWg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTXN-0003Xe-JA; Wed, 06 May 2020 23:33:13 +0000 Received: from mx.baikalelectronics.com ([94.125.187.42] helo=mail.baikalelectronics.ru) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jWTWB-000281-Bm; Wed, 06 May 2020 23:32:01 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id 90CC580307C7; Wed, 6 May 2020 23:31:58 +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 wKfdVf1ADvRI; Thu, 7 May 2020 02:31:57 +0300 (MSK) From: Serge Semin To: Thomas Bogendoerfer , Greg Kroah-Hartman , Jiri Slaby , Andy Shevchenko Subject: [PATCH v3 4/4] serial: 8250_dw: Fix common clocks usage race condition Date: Thu, 7 May 2020 02:31:35 +0300 Message-ID: <20200506233136.11842-5-Sergey.Semin@baikalelectronics.ru> In-Reply-To: <20200506233136.11842-1-Sergey.Semin@baikalelectronics.ru> References: <20200323024611.16039-1-Sergey.Semin@baikalelectronics.ru> <20200506233136.11842-1-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-20200506_163159_796576_D6C65E28 X-CRM114-Status: GOOD ( 24.31 ) X-Spam-Score: 0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on bombadil.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-mediatek@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 , Kefeng Wang , Heikki Krogerus , linux-kernel@vger.kernel.org, Paul Burton , Arnd Bergmann , Catalin Marinas , Russell King , Ralf Baechle , Alexey Malahov , Serge Semin , Long Cheng , linux-mediatek@lists.infradead.org, Serge Semin , linux-serial@vger.kernel.org, linux-mips@vger.kernel.org, Will Deacon , linux-arm-kernel@lists.infradead.org Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+patchwork-linux-mediatek=patchwork.kernel.org@lists.infradead.org The race condition may happen if the UART reference clock is shared with some other device (on Baikal-T1 SoC it's another DW UART port). In this case if that device changes the clock rate while serial console is using it the DW 8250 UART port might not only end up with an invalid uartclk value saved, but may also experience a distorted output data since baud-clock could have been changed. In order to fix this lets at least try to adjust the 8250 port setting like UART clock rate in case if the reference clock rate change is discovered. The driver will call the new method to update 8250 UART port clock rate settings. It's done by means of the clock event notifier registered at the port startup and unregistered in the shutdown callback method. Note 1. In order to avoid deadlocks we had to execute the UART port update method in a dedicated deferred work. This is due to (in my opinion redundant) the clock update implemented in the dw8250_set_termios() method. Note 2. Before the ref clock is manually changed by the custom set_termios() function we swap the port uartclk value with new rate adjusted to be suitable for the requested baud. It is necessary in order to effectively disable a functionality of the ref clock events handler for the current UART port, since uartclk update will be done a bit further in the generic serial8250_do_set_termios() function. Signed-off-by: Serge Semin Cc: Alexey Malahov Cc: Thomas Bogendoerfer Cc: Paul Burton Cc: Ralf Baechle Cc: Arnd Bergmann Cc: Long Cheng Cc: Andy Shevchenko Cc: Maxime Ripard Cc: Catalin Marinas Cc: Will Deacon Cc: Russell King Cc: linux-mips@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-mediatek@lists.infradead.org --- Changelog v2: - Move exclusive ref clock lock/unlock precudures to the 8250 port startup/shutdown methods. - The changelog message has also been slightly modified due to the alteration. - Remove Alexey' SoB tag. - Cc someone from ARM who might be concerned regarding this change. - Cc someone from Clocks Framework to get their comments on this patch. Changelog v3: - Refactor the original patch to adjust the UART port divisor instead of requesting an exclusive ref clock utilization. --- drivers/tty/serial/8250/8250_dw.c | 114 +++++++++++++++++++++++++++++- 1 file changed, 111 insertions(+), 3 deletions(-) diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c index 12866083731d..cf4de510ab1b 100644 --- a/drivers/tty/serial/8250/8250_dw.c +++ b/drivers/tty/serial/8250/8250_dw.c @@ -19,6 +19,8 @@ #include #include #include +#include +#include #include #include #include @@ -43,6 +45,8 @@ struct dw8250_data { int msr_mask_off; struct clk *clk; struct clk *pclk; + struct notifier_block clk_notifier; + struct work_struct clk_work; struct reset_control *rst; unsigned int skip_autocfg:1; @@ -54,6 +58,16 @@ static inline struct dw8250_data *to_dw8250_data(struct dw8250_port_data *data) return container_of(data, struct dw8250_data, data); } +static inline struct dw8250_data *clk_to_dw8250_data(struct notifier_block *nb) +{ + return container_of(nb, struct dw8250_data, clk_notifier); +} + +static inline struct dw8250_data *work_to_dw8250_data(struct work_struct *work) +{ + return container_of(work, struct dw8250_data, clk_work); +} + static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value) { struct dw8250_data *d = to_dw8250_data(p->private_data); @@ -260,6 +274,45 @@ static int dw8250_handle_irq(struct uart_port *p) return 0; } +static void dw8250_clk_work_cb(struct work_struct *work) +{ + struct dw8250_data *d = work_to_dw8250_data(work); + struct uart_8250_port *up; + unsigned long rate; + + rate = clk_get_rate(d->clk); + if (rate) { + up = serial8250_get_port(d->data.line); + + serial8250_update_uartclk(&up->port, rate); + } +} + +static int dw8250_clk_notifier_cb(struct notifier_block *nb, + unsigned long event, void *data) +{ + struct dw8250_data *d = clk_to_dw8250_data(nb); + + /* + * We have no choice but to defer the uartclk update due to two + * deadlocks. First one is caused by a recursive mutex lock which + * happens when clk_set_rate() is called from dw8250_set_termios(). + * Second deadlock is more tricky and is caused by an inverted order of + * the clk and tty-port mutexes lock. It happens if clock rate change + * is requested asynchronously while set_termios() is executed between + * tty-port mutex lock and clk_set_rate() function invocation and + * vise-versa. Anyway if we didn't have the reference clock alteration + * in the dw8250_set_termios() method we wouldn't have needed this + * deferred event handling complication. + */ + if (event == POST_RATE_CHANGE) { + queue_work(system_unbound_wq, &d->clk_work); + return NOTIFY_OK; + } + + return NOTIFY_DONE; +} + static void dw8250_do_pm(struct uart_port *port, unsigned int state, unsigned int old) { @@ -283,9 +336,16 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios, clk_disable_unprepare(d->clk); rate = clk_round_rate(d->clk, baud * 16); if (rate > 0) { - ret = clk_set_rate(d->clk, rate); - if (!ret) - p->uartclk = rate; + /* + * Premilinary set the uartclk to the new clock rate so the + * clock update event handler caused by the clk_set_rate() + * calling wouldn't actually update the UART divisor since + * we about to do this anyway. + */ + swap(p->uartclk, rate); + ret = clk_set_rate(d->clk, p->uartclk); + if (ret) + swap(p->uartclk, rate); } clk_prepare_enable(d->clk); @@ -312,6 +372,49 @@ static void dw8250_set_ldisc(struct uart_port *p, struct ktermios *termios) serial8250_do_set_ldisc(p, termios); } +static int dw8250_startup(struct uart_port *p) +{ + struct dw8250_data *d = to_dw8250_data(p->private_data); + int ret; + + /* + * Some platforms may provide a reference clock shared between several + * devices. In this case before using the serial port first we have to + * make sure that any clock state change is known to the UART port at + * least post factum. + */ + if (d->clk) { + ret = clk_notifier_register(d->clk, &d->clk_notifier); + if (ret) + dev_warn(p->dev, "Failed to set the clock notifier\n"); + + /* + * Get current reference clock rate to make sure the UART port + * is equipped with an up-to-date value before it's started up. + */ + p->uartclk = clk_get_rate(d->clk); + if (!p->uartclk) { + dev_err(p->dev, "Clock rate not defined\n"); + return -EINVAL; + } + } + + return serial8250_do_startup(p); +} + +static void dw8250_shutdown(struct uart_port *p) +{ + struct dw8250_data *d = to_dw8250_data(p->private_data); + + serial8250_do_shutdown(p); + + if (d->clk) { + clk_notifier_unregister(d->clk, &d->clk_notifier); + + flush_work(&d->clk_work); + } +} + /* * dw8250_fallback_dma_filter will prevent the UART from getting just any free * channel on platforms that have DMA engines, but don't have any channels @@ -407,6 +510,8 @@ static int dw8250_probe(struct platform_device *pdev) p->serial_out = dw8250_serial_out; p->set_ldisc = dw8250_set_ldisc; p->set_termios = dw8250_set_termios; + p->startup = dw8250_startup; + p->shutdown = dw8250_shutdown; p->membase = devm_ioremap(dev, regs->start, resource_size(regs)); if (!p->membase) @@ -468,6 +573,9 @@ static int dw8250_probe(struct platform_device *pdev) if (IS_ERR(data->clk)) return PTR_ERR(data->clk); + INIT_WORK(&data->clk_work, dw8250_clk_work_cb); + data->clk_notifier.notifier_call = dw8250_clk_notifier_cb; + err = clk_prepare_enable(data->clk); if (err) dev_warn(dev, "could not enable optional baudclk: %d\n", err);