From patchwork Mon Sep 19 15:08:47 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergiu Moga X-Patchwork-Id: 12980625 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 391E2C6FA91 for ; Mon, 19 Sep 2022 15:15:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230073AbiISPPH (ORCPT ); Mon, 19 Sep 2022 11:15:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229875AbiISPOr (ORCPT ); Mon, 19 Sep 2022 11:14:47 -0400 Received: from esa.microchip.iphmx.com (esa.microchip.iphmx.com [68.232.154.123]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 20245357D8; Mon, 19 Sep 2022 08:14:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=microchip.com; i=@microchip.com; q=dns/txt; s=mchp; t=1663600460; x=1695136460; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=c870c32AhfgZVg4pwd9ZMePlL4mjnVCOQA4N7lzg7uk=; b=k60+i5P5Mqyl8vfrc1i+E1GdVv6KyNK+2bguKeMU95I3ACooU2eHHgkd U2FUrfHj+dkYm7W3mLRABpD/Mh8XRGgIjtbUYeOeQ/9JE+fIXcVb8GVT4 Fw/qzGqFNIy4KlA7VSJLqXIw614mloVUq6kmbaF19zFcqTK7vl8E5Pnh0 JQqijtCIUzB/+YLNky7fiYYPepD2z2cKyZvIk/9YrZDbwXfGWHeQ9oTx8 TfthvTR+nY/ysH1UYups6CpvsO21qmDUFW8wK5/ofYzR3iR3kojrtNfIs 54jLBMeF2SFzhvrz8gRZsiDcn65t13Wv+0ZKkFXxjB65sMCa5IoatevgV w==; X-IronPort-AV: E=Sophos;i="5.93,328,1654585200"; d="scan'208";a="114368422" Received: from unknown (HELO email.microchip.com) ([170.129.1.10]) by esa6.microchip.iphmx.com with ESMTP/TLS/AES256-SHA256; 19 Sep 2022 08:14:19 -0700 Received: from chn-vm-ex03.mchp-main.com (10.10.85.151) by chn-vm-ex02.mchp-main.com (10.10.85.144) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.12; Mon, 19 Sep 2022 08:14:17 -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; Mon, 19 Sep 2022 08:14:13 -0700 From: Sergiu Moga To: , , , , , , , , , , CC: , , , , , Sergiu Moga Subject: [PATCH v4 9/9] tty: serial: atmel: Make the driver aware of the existence of GCLK Date: Mon, 19 Sep 2022 18:08:47 +0300 Message-ID: <20220919150846.1148783-10-sergiu.moga@microchip.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220919150846.1148783-1-sergiu.moga@microchip.com> References: <20220919150846.1148783-1-sergiu.moga@microchip.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.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 Reviewed-by: Claudiu Beznea --- 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 the error rate calculation function as an inline function instead of a macro definition - add `gclk_fail` goto - replace `goto err` with `goto err_clk_disable_unprepare;` v3 -> v4: - Nothing, this was previously [PATCH 14] 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 c983798a4ab2..426f9d4f9a5a 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 = min_t(unsigned int, 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;