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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5F253C4332F for ; Fri, 15 Apr 2022 13:37:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354074AbiDONkN (ORCPT ); Fri, 15 Apr 2022 09:40:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1354114AbiDONkE (ORCPT ); Fri, 15 Apr 2022 09:40:04 -0400 Received: from mail-sh.amlogic.com (mail-sh.amlogic.com [58.32.228.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9B41B11C31; Fri, 15 Apr 2022 06:35:52 -0700 (PDT) Received: from [10.18.29.47] (10.18.29.47) by mail-sh.amlogic.com (10.18.11.5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2176.14; Fri, 15 Apr 2022 21:35:45 +0800 Message-ID: <77c83f45-3782-624d-36c4-dec5c53cdd09@amlogic.com> Date: Fri, 15 Apr 2022 21:35:44 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH 2/3] tty: serial: meson: Added 12Mhz as the clock source for calculating baud rate Content-Language: en-US To: Neil Armstrong , , , , , Kevin Hilman , Jerome Brunet CC: Greg Kroah-Hartman , Jiri Slaby , Martin Blumenstingl References: <20220407081355.13602-1-yu.tu@amlogic.com> <20220407081355.13602-3-yu.tu@amlogic.com> From: Yu Tu In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.18.29.47] X-ClientProxiedBy: mail-sh.amlogic.com (10.18.11.5) To mail-sh.amlogic.com (10.18.11.5) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Neil, Thank you for your reply. On 2022/4/7 22:03, Neil Armstrong wrote: > [ EXTERNAL EMAIL ] > > On 07/04/2022 10:13, Yu Tu wrote: >> Starting with the g12A chip, add a 12Mhz clock to calculate the baud >> rate, since the BT module uses 3Mhz baud rate. 8Mhz calculations can >> lead to baud rate bias, causing some problems. > > The commit message isn't clear enough, 12MHz is a new intermediate clock > rate, not a new clock source of the UART module. > > Please explain a /2 divider over XTAL was introduced since G12A, and > is preferred to be used over the still present /3 divider since it > provides much closer frequencies vs the request baudrate. > I will prepare the next version of the code as you requested. >> >> Signed-off-by: Yu Tu >> --- >>   drivers/tty/serial/meson_uart.c | 25 +++++++++++++++++++++++-- >>   1 file changed, 23 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/tty/serial/meson_uart.c >> b/drivers/tty/serial/meson_uart.c >> index 8e59624935af..7e77693a1318 100644 >> --- a/drivers/tty/serial/meson_uart.c >> +++ b/drivers/tty/serial/meson_uart.c >> @@ -68,6 +68,7 @@ >>   #define AML_UART_BAUD_MASK        0x7fffff >>   #define AML_UART_BAUD_USE        BIT(23) >>   #define AML_UART_BAUD_XTAL        BIT(24) >> +#define AML_UART_BAUD_XTAL_DIV2        BIT(27) >>   #define AML_UART_PORT_NUM        12 >>   #define AML_UART_PORT_OFFSET        6 >> @@ -80,6 +81,10 @@ static struct uart_driver meson_uart_driver; >>   static struct uart_port *meson_ports[AML_UART_PORT_NUM]; >> +struct meson_uart_data { >> +    bool has_xtal_div2; >> +}; >> + >>   static void meson_uart_set_mctrl(struct uart_port *port, unsigned >> int mctrl) >>   { >>   } >> @@ -293,13 +298,20 @@ static int meson_uart_startup(struct uart_port >> *port) >>   static void meson_uart_change_speed(struct uart_port *port, unsigned >> long baud) >>   { >> -    u32 val; >> +    struct meson_uart_data *private_data = port->private_data; >> +    u32 val = 0; >>       while (!meson_uart_tx_empty(port)) >>           cpu_relax(); >>       if (port->uartclk == 24000000) { >> -        val = DIV_ROUND_CLOSEST(port->uartclk / 3, baud) - 1; >> +        unsigned int xtal_div = 3; >> + >> +        if (private_data->has_xtal_div2) { >> +            xtal_div = 2; >> +            val |= AML_UART_BAUD_XTAL_DIV2; >> +        } >> +        val |= DIV_ROUND_CLOSEST(port->uartclk / xtal_div, baud) - 1; >>           val |= AML_UART_BAUD_XTAL; >>       } else { >>           val =  DIV_ROUND_CLOSEST(port->uartclk / 4, baud) - 1; >> @@ -691,6 +703,7 @@ static int meson_uart_probe_clocks(struct >> platform_device *pdev, >>   static int meson_uart_probe(struct platform_device *pdev) >>   { >> +    struct meson_uart_data *private_data; >>       struct resource *res_mem; >>       struct uart_port *port; >>       u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */ >> @@ -733,6 +746,13 @@ static int meson_uart_probe(struct >> platform_device *pdev) >>       if (!port) >>           return -ENOMEM; >> +    private_data = devm_kzalloc(&pdev->dev, sizeof(struct >> meson_uart_data), GFP_KERNEL); >> +    if (!private_data) >> +        return -ENOMEM; >> + >> +    if ((bool)device_get_match_data(&pdev->dev)) >> +        private_data->has_xtal_div2 = true; > > It should be much cleaner to pass meson_uart_data to meson_uart_dt_match > .data, > and then you can retrieve device_get_match_data() and put the result into > port->private_data. > This will avoid a devm_kzalloc(). > > Then in meson_uart_change_speed() change the test to check for NULL > private_data: > if (private_data && private_data->has_xtal_div2) > >> + >>       ret = meson_uart_probe_clocks(pdev, port); >>       if (ret) >>           return ret; >> @@ -749,6 +769,7 @@ static int meson_uart_probe(struct platform_device >> *pdev) >>       port->x_char = 0; >>       port->ops = &meson_uart_ops; >>       port->fifosize = fifosize; >> +    port->private_data = private_data; >>       meson_ports[pdev->id] = port; >>       platform_set_drvdata(pdev, port); > > Neil > I will prepare the next version of the code as you requested. > .