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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id CA671ECAAD3 for ; Wed, 7 Sep 2022 09:49:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:Message-ID: In-Reply-To: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=/YJBQLa38UvaQ0T5Z8s7g/hJsb5WxZ5Z6CIrFmwl43A=; b=3uU1s5Ag62bheh /t/vyQKBVr+Tz6nYav6ISxORyd85GmaG1pmwX3TWtpLkka5QG0h5C7hl1GBHtxoJyeLSx1aA4EkW3 aiLhjeROiOuJOOw6rTjbSWmZS6ELeXnXYiH0rFFtuLQSn2V+pci4wcRUTv39FwbYE7Z/yx8RjmVT6 p3CvQxLRSm52bYlQXlfIwCChgOj3BwTbsn9mMZ4Ls8HGECub+FZ+eLLkEhQpp0VPldMYbi9HysiGJ N4r6hwOxelfPZMspNSb3SV9QJg52zcqRQxsgyqsW6ZzxV/DpT2zbFZ5FErLDqDQxWtFyVvJcf5zTH han86kuViMfSMm+MYIRQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oVrfN-0052qd-8Q; Wed, 07 Sep 2022 09:48:17 +0000 Received: from mga02.intel.com ([134.134.136.20]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oVrU1-004x7R-MD for linux-arm-kernel@lists.infradead.org; Wed, 07 Sep 2022 09:36:35 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1662543393; x=1694079393; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=tKw3aYgjO5ai6ZJTrD5+c07/ZCZv2dQ4amjcz1mH21A=; b=KDN+Uw/jy7C3HOraPUepJiMxhZOkh3pW+DcU0gvZlPEi81EpZtKUcjaF +VKQ7942eOlEY9Wfp+db+RaseKwuHp9civgtM4lLusEtdCxkG6qduMM3N YTxOR/2ShZGoz4AGZIkt3BHV71sfs+bVt6aO2r5g8z0pzZQ1/tds6+4hC 8y/vPtnojPju9gwRSW8rwmK0sbr/uSjr4JhWgVi8pKNhmbhTYnCBLj7Bg szhOdAr59Q7ZMa7e0hp7fMLi4kDyTQdZw5bYngQlgKG/QSVNQ6s4kApGy bKNWrlU6f8tAtUMGoP8apC94zlHQkH57+SVQyNHvKlMwKI2LEC1nYbZSh w==; X-IronPort-AV: E=McAfee;i="6500,9779,10462"; a="283825217" X-IronPort-AV: E=Sophos;i="5.93,296,1654585200"; d="scan'208";a="283825217" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Sep 2022 02:36:29 -0700 X-IronPort-AV: E=Sophos;i="5.93,296,1654585200"; d="scan'208";a="676101846" Received: from dmatouse-mobl.ger.corp.intel.com ([10.251.223.53]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Sep 2022 02:36:23 -0700 Date: Wed, 7 Sep 2022 12:36:22 +0300 (EEST) From: =?ISO-8859-15?Q?Ilpo_J=E4rvinen?= To: Sergiu Moga Subject: Re: [PATCH v2 12/13] tty: serial: atmel: Make the driver aware of the existence of GCLK In-Reply-To: <20220906135511.144725-13-sergiu.moga@microchip.com> Message-ID: <3f98d634-789-a0bd-84e-cfc2a1de70af@linux.intel.com> References: <20220906135511.144725-1-sergiu.moga@microchip.com> <20220906135511.144725-13-sergiu.moga@microchip.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220907_023633_849957_60E6B411 X-CRM114-Status: GOOD ( 36.95 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: alexandre.belloni@bootlin.com, mturquette@baylibre.com, LKML , admin@hifiphile.com, krzysztof.kozlowski+dt@linaro.org, Jiri Slaby , linux-clk@vger.kernel.org, lee@kernel.org, linux-serial , devicetree@vger.kernel.org, tudor.ambarus@microchip.com, radu_nicolae.pirea@upb.ro, robh+dt@kernel.org, linux-arm-kernel@lists.infradead.org, richard.genoud@gmail.com, Greg Kroah-Hartman , linux-spi@vger.kernel.org, sboyd@kernel.org, broonie@kernel.org, kavyasree.kotagiri@microchip.com, claudiu.beznea@microchip.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 6 Sep 2022, Sergiu Moga wrote: > Previously, the atmel serial driver did not take into account the > possibility of using the more customizable generic clock as its > baudrate generator. Unless there is a Fractional Part available to > increase accuracy, there is a high chance that we may be able to > generate a baudrate closer to the desired one by using the GCLK as the > clock source. Now, depending on the error rate between > the desired baudrate and the actual baudrate, the serial driver will > fallback on the generic clock. The generic clock must be provided > in the DT node of the serial that may need a more flexible clock source. > > Signed-off-by: Sergiu Moga > --- > > > > v1 -> v2: > - take into account the different placement of the baudrate clock source > into the IP's Mode Register (USART vs UART) > - don't check for atmel_port->gclk != NULL > - use clk_round_rate instead of clk_set_rate + clk_get_rate > - remove clk_disable_unprepare from the end of the probe method > > > > drivers/tty/serial/atmel_serial.c | 52 ++++++++++++++++++++++++++++++- > 1 file changed, 51 insertions(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c > index 6aa01ca5489c..b2b6fd6ea2a5 100644 > --- a/drivers/tty/serial/atmel_serial.c > +++ b/drivers/tty/serial/atmel_serial.c > @@ -15,6 +15,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -77,6 +78,8 @@ static void atmel_stop_rx(struct uart_port *port); > #endif > > #define ATMEL_ISR_PASS_LIMIT 256 > +#define ERROR_RATE(desired_value, actual_value) \ > + ((int)(100 - ((desired_value) * 100) / (actual_value))) Make a function instead. Is percent accurate enough or would you perhaps want something slightly more accurate? Given you've abs() at the caller side, the error rate could be underestimated, is underestimating OK? -- i. > struct atmel_dma_buffer { > unsigned char *buf; > @@ -110,6 +113,7 @@ struct atmel_uart_char { > struct atmel_uart_port { > struct uart_port uart; /* uart */ > struct clk *clk; /* uart clock */ > + struct clk *gclk; /* uart generic clock */ > int may_wakeup; /* cached value of device_may_wakeup for times we need to disable it */ > u32 backup_imr; /* IMR saved during suspend */ > int break_active; /* break being received */ > @@ -2117,6 +2121,8 @@ static void atmel_serial_pm(struct uart_port *port, unsigned int state, > * This is called on uart_close() or a suspend event. > */ > clk_disable_unprepare(atmel_port->clk); > + if (__clk_is_enabled(atmel_port->gclk)) > + clk_disable_unprepare(atmel_port->gclk); > break; > default: > dev_err(port->dev, "atmel_serial: unknown pm %d\n", state); > @@ -2131,7 +2137,8 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, > { > struct atmel_uart_port *atmel_port = to_atmel_uart_port(port); > unsigned long flags; > - unsigned int old_mode, mode, imr, quot, baud, div, cd, fp = 0; > + unsigned int old_mode, mode, imr, quot, div, cd, fp = 0; > + unsigned int baud, actual_baud, gclk_rate; > > /* save the current mode register */ > mode = old_mode = atmel_uart_readl(port, ATMEL_US_MR); > @@ -2297,6 +2304,43 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios, > cd &= 65535; > } > > + /* > + * If there is no Fractional Part, there is a high chance that > + * we may be able to generate a baudrate closer to the desired one > + * if we use the GCLK as the clock source driving the baudrate > + * generator. > + */ > + if (!atmel_port->has_frac_baudrate) { > + if (__clk_is_enabled(atmel_port->gclk)) > + clk_disable_unprepare(atmel_port->gclk); > + gclk_rate = clk_round_rate(atmel_port->gclk, 16 * baud); > + actual_baud = clk_get_rate(atmel_port->clk) / (16 * cd); > + if (gclk_rate && abs(ERROR_RATE(baud, actual_baud)) > > + abs(ERROR_RATE(baud, gclk_rate / 16))) { > + clk_set_rate(atmel_port->gclk, 16 * baud); > + if (!clk_prepare_enable(atmel_port->gclk)) { > + if (atmel_port->is_usart) { > + mode &= ~ATMEL_US_USCLKS; > + mode |= ATMEL_US_USCLKS_GCLK; > + } else { > + mode &= ~ATMEL_UA_BRSRCCK; > + mode |= ATMEL_UA_BRSRCCK_GCLK; > + } > + > + /* > + * Set the Clock Divisor for GCLK to 1. > + * Since we were able to generate the smallest > + * multiple of the desired baudrate times 16, > + * then we surely can generate a bigger multiple > + * with the exact error rate for an equally increased > + * CD. Thus no need to take into account > + * a higher value for CD. > + */ > + cd = 1; > + } > + } > + } > + > quot = cd | fp << ATMEL_US_FP_OFFSET; > > if (!(port->iso7816.flags & SER_ISO7816_ENABLED)) > @@ -2892,6 +2936,12 @@ static int atmel_serial_probe(struct platform_device *pdev) > if (ret) > goto err; > > + atmel_port->gclk = devm_clk_get_optional(&pdev->dev, "gclk"); > + if (IS_ERR(atmel_port->gclk)) { > + ret = PTR_ERR(atmel_port->gclk); > + goto err; > + } > + > ret = atmel_init_port(atmel_port, pdev); > if (ret) > goto err_clk_disable_unprepare; > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel