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 X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 30164C433E0 for ; Fri, 15 May 2020 14:33:34 +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 00EEF2076A for ; Fri, 15 May 2020 14:33:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="sTmQDkED" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 00EEF2076A 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+linux-mediatek=archiver.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:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=0qqORSX91pVXn6gKJ7ax2liWfijFsqZzukC9jIHwPbk=; b=sTmQDkEDtV4wfW 8EOJh0W6zSqLrgBwYMsMSdWA6EHn/h00Szx4swyGn4TLiapNRusGRXfJZKtbCm3vtLkhN2L2i58SD AI2sR9U34ZhiAul/B1XIL6UnYbUhoZ0zy1c1dOXMWTFS3sVfofu8GE23DskKOJ0wVxz37ApMuGNcM llhrHhIgpO4fhy+f3XL3YjjzbIrZXGAClqyEXaEWifxv98H7a0M3cX0GvwhWx3XgWJWdanzz1OD0P qWyBjZaUWSv4bXid2NOKPLGOkkMGzynhWDOUMfG3xtZ4AAjaQyhlvEyzoN/iH8gqmJNCmeTrCg1H3 aPc5XKNLJkr8S3qHcmDA==; 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 1jZbOs-0000vv-Hc; Fri, 15 May 2020 14:33:22 +0000 Received: from mail.baikalelectronics.com ([87.245.175.226] helo=mail.baikalelectronics.ru) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jZbOi-0000oC-Lh; Fri, 15 May 2020 14:33:15 +0000 Received: from localhost (unknown [127.0.0.1]) by mail.baikalelectronics.ru (Postfix) with ESMTP id DB4C080004AB; Fri, 15 May 2020 14:33:01 +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 DGjAxQRrTWZS; Fri, 15 May 2020 17:32:57 +0300 (MSK) Date: Fri, 15 May 2020 17:32:54 +0300 From: Serge Semin To: Greg Kroah-Hartman Subject: Re: [PATCH v3 2/4] serial: 8250: Add 8250 port clock update method Message-ID: <20200515143254.oicqdkvvh6zkuqyl@mobilestation> References: <20200323024611.16039-1-Sergey.Semin@baikalelectronics.ru> <20200506233136.11842-1-Sergey.Semin@baikalelectronics.ru> <20200506233136.11842-3-Sergey.Semin@baikalelectronics.ru> <20200515124525.GA1888557@kroah.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200515124525.GA1888557@kroah.com> 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-20200515_073313_068698_E0F3E071 X-CRM114-Status: GOOD ( 20.81 ) 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, Jiri Slaby , Arnd Bergmann , Maxime Ripard , Alexey Malahov , linux-mediatek@lists.infradead.org, Thomas Gleixner , Andy Shevchenko , Mika Westerberg , Allison Randal , Thomas Bogendoerfer , linux-mips@vger.kernel.org, Ralf Baechle , linux-kernel@vger.kernel.org, Lukas Wunner Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org On Fri, May 15, 2020 at 02:45:25PM +0200, Greg Kroah-Hartman wrote: > On Thu, May 07, 2020 at 02:31:33AM +0300, Serge Semin wrote: > > 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); > > EXPORT_SYMBOL_GPL() please. Ok. I guess I've just copied the line from some of the export symbol statements below. My mistake. Sorry. -Sergey > > thanks, > > greg k-h _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek