From patchwork Tue Sep 13 14:22:06 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergiu Moga X-Patchwork-Id: 12974868 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 C4D3EC54EE9 for ; Tue, 13 Sep 2022 14:45:13 +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:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=4hGriilsmLP7NsyRoqXHi6IhmT0JQ67QazI0c65fP/k=; b=NHev/eIQBe2D/s R2/nK9hVsCMBVZKcvn0iqWJss5nbghYEYx3txO/AsfvKrnopCifk4SLDtzH7ctCaT/gTq0uw9GNh7 8cCVRm1yPmsc6KPzjupDbh32B9INBWv2aG4vjrF/wbIm/+VG27czPfdGUwY9RAWDjd/H8svBSDJvx vNWWLxn2MKP1Gf4k4OAMpP8mx2xFw4JJ8pJfCU5CbZrqMBIgygRlyese/iV0Pn5s0F5cNACqiQiQA WcUvvV2H0kVUIJNL175/ZLPpXoCtvPZdRVMfYATEcDGo8d7ZIKDp1ET6dnOpPNB0p4iXNOAK10QxR ko6tmIBsptkGBHFUJc7A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oY78f-00BprT-5u; Tue, 13 Sep 2022 14:43:49 +0000 Received: from esa.microchip.iphmx.com ([68.232.153.233]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oY6rR-00BZIo-AM for linux-arm-kernel@lists.infradead.org; Tue, 13 Sep 2022 14:26:04 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=microchip.com; i=@microchip.com; q=dns/txt; s=mchp; t=1663079160; x=1694615160; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=8YHtuNpkGgonB15jpX0l3ZBjbodkb/o7uCM4zW7bTXA=; b=zYzJ/MMTVuMmcFxb+Rm/6n605CxyiqLyvVgnDnOp7/zbW8MGzYR4KFLd qzfL0aRMoo26YEr5okiQbX2JGWRquCuVOq/16CPs0H4nOTAkUACHl24l2 E733qwdub7gGnxH565Cvi483IGdfMk+Wl1pSdA/+x+UE72UqHvH8/syyA DMtGwGnvsP1I0uGxT2qY26Ht1gfIP9i29v9LocfPevl8+cB7i0B6kvlD/ l5qL+jHTSCYeUvkAvX4FG3mkgWFj/hvcEyuRSXTXdxRJhm/EVlI1DA58y SJcORWz05MVjFQS1zM8QFbaKhLHftemuCcJ42t2vRGYMGmA3JCSNJuknK w==; X-IronPort-AV: E=Sophos;i="5.93,313,1654585200"; d="scan'208";a="180313690" Received: from unknown (HELO email.microchip.com) ([170.129.1.10]) by esa3.microchip.iphmx.com with ESMTP/TLS/AES256-SHA256; 13 Sep 2022 07:25:59 -0700 Received: from chn-vm-ex03.mchp-main.com (10.10.85.151) by chn-vm-ex01.mchp-main.com (10.10.85.143) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.12; Tue, 13 Sep 2022 07:25:59 -0700 Received: from ROB-ULT-M68701.microchip.com (10.10.115.15) by chn-vm-ex03.mchp-main.com (10.10.85.151) with Microsoft SMTP Server id 15.1.2507.12 via Frontend Transport; Tue, 13 Sep 2022 07:25:54 -0700 From: Sergiu Moga To: , , , , , , , , , , , , , , , , CC: , , , , , Subject: [PATCH v3 14/14] tty: serial: atmel: Make the driver aware of the existence of GCLK Date: Tue, 13 Sep 2022 17:22:06 +0300 Message-ID: <20220913142205.162399-15-sergiu.moga@microchip.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220913142205.162399-1-sergiu.moga@microchip.com> References: <20220913142205.162399-1-sergiu.moga@microchip.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220913_072601_521360_F9F05990 X-CRM114-Status: GOOD ( 24.85 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 v2 -> v3: - add `gclk_fail` goto - replace `goto err` with `goto err_clk_disable_unprepare;` drivers/tty/serial/atmel_serial.c | 59 ++++++++++++++++++++++++++++++- 1 file changed, 58 insertions(+), 1 deletion(-) diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c index ad7483230090..920548c55c25 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 @@ -110,6 +111,7 @@ 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 */ @@ -229,6 +231,11 @@ static inline int atmel_uart_is_half_duplex(struct uart_port *port) (port->iso7816.flags & SER_ISO7816_ENABLED); } +static inline int atmel_error_rate(int desired_value, int actual_value) +{ + return 100 - (desired_value * 100) / actual_value; +} + #ifdef CONFIG_SERIAL_ATMEL_PDC static bool atmel_use_pdc_rx(struct uart_port *port) { @@ -2117,6 +2124,8 @@ 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); @@ -2132,7 +2141,9 @@ static void atmel_set_termios(struct uart_port *port, { 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; + int ret; /* save the current mode register */ mode = old_mode = atmel_uart_readl(port, ATMEL_US_MR); @@ -2302,6 +2313,46 @@ static void atmel_set_termios(struct uart_port *port, cd &= ATMEL_US_CD; } + /* + * 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(atmel_error_rate(baud, actual_baud)) > + abs(atmel_error_rate(baud, gclk_rate / 16))) { + clk_set_rate(atmel_port->gclk, 16 * baud); + ret = clk_prepare_enable(atmel_port->gclk); + if (ret) + goto gclk_fail; + + 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; + } + } + +gclk_fail: quot = cd | fp << ATMEL_US_FP_OFFSET; if (!(port->iso7816.flags & SER_ISO7816_ENABLED)) @@ -2897,6 +2948,12 @@ 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_clk_disable_unprepare; + } + ret = atmel_init_port(atmel_port, pdev); if (ret) goto err_clk_disable_unprepare;