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 B9E1FC77B73 for ; Mon, 5 Jun 2023 06:16:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229590AbjFEGPT (ORCPT ); Mon, 5 Jun 2023 02:15:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42026 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229459AbjFEGPR (ORCPT ); Mon, 5 Jun 2023 02:15:17 -0400 Received: from muru.com (muru.com [72.249.23.125]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 038D6DB; Sun, 4 Jun 2023 23:15:13 -0700 (PDT) Received: from localhost (localhost [127.0.0.1]) by muru.com (Postfix) with ESMTPS id 0E00A80C1; Mon, 5 Jun 2023 06:15:13 +0000 (UTC) Date: Mon, 5 Jun 2023 09:15:11 +0300 From: Tony Lindgren To: John Ogness Cc: Chen-Yu Tsai , Greg Kroah-Hartman , Jiri Slaby , Andy Shevchenko , Dhruva Gole , Ilpo =?utf-8?B?SsOkcnZpbmVu?= , Johan Hovold , Sebastian Andrzej Siewior , Vignesh Raghavendra , linux-omap@vger.kernel.org, Andy Shevchenko , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, =?utf-8?B?TsOtY29sYXMgRi4gUi4gQS4=?= Prado , AngeloGioacchino Del Regno , linux-mediatek@lists.infradead.org Subject: Re: [PATCH v12 1/1] serial: core: Start managing serial controllers to enable runtime PM Message-ID: <20230605061511.GW14287@atomide.com> References: <20230525113034.46880-1-tony@atomide.com> <20230602083335.GA181647@google.com> <87a5xii33r.fsf@jogness.linutronix.de> <20230603054139.GR14287@atomide.com> <20230603063533.GS14287@atomide.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230603063533.GS14287@atomide.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Tony Lindgren [230603 06:35]: > * Tony Lindgren [230603 05:41]: > > I don't think 8250_mtk needs to do register access before and after the > > serial port registration, but if it does, then adding custom read/write > > functions can be done that do not rely on initialized port like > > serial_out(). > > Oh but mtk8250_runtime_suspend() calls serial_in(up, MTK_UART_DEBUG0), so > yeah if that gets called before registration is complete it causes a NULL > pointer exception. If the serial_ctrl and serial_port devices do runtime > suspend before port registration completes, things will fail. > > Sounds like doing pm_runtime_resume_and_get() in mtk8250_probe() might > fix the issue. Still seems that adding a custom read function for > mtk8250_runtime_suspend() to use instead of calling serial_in() should > not be needed. Looking at this again, if serial8250_register_8250_port() fails, then mtk8250_runtime_suspend() would again try to access uninitialized port. Here's a better untested version of the patch to try. Regards, Tony 8< --------------------------- diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c --- a/drivers/tty/serial/8250/8250_mtk.c +++ b/drivers/tty/serial/8250/8250_mtk.c @@ -57,6 +57,8 @@ #define MTK_UART_XON1 40 /* I/O: Xon character 1 */ #define MTK_UART_XOFF1 42 /* I/O: Xoff character 1 */ +#define MTK_UART_REGSHIFT 2 + #ifdef CONFIG_SERIAL_8250_DMA enum dma_rx_status { DMA_RX_START = 0, @@ -69,6 +71,7 @@ struct mtk8250_data { int line; unsigned int rx_pos; unsigned int clk_count; + void __iomem *membase; struct clk *uart_clk; struct clk *bus_clk; struct uart_8250_dma *dma; @@ -187,6 +190,17 @@ static void mtk8250_dma_enable(struct uart_8250_port *up) } #endif +/* Read and write for register access before and after port registration */ +static u32 __maybe_unused mtk8250_read(struct mtk8250_data *data, u32 reg) +{ + return readl(data->membase + (reg << MTK_UART_REGSHIFT)); +} + +static void mtk8250_write(struct mtk8250_data *data, u32 reg, u32 val) +{ + writel(val, data->membase + (reg << MTK_UART_REGSHIFT)); +} + static int mtk8250_startup(struct uart_port *port) { #ifdef CONFIG_SERIAL_8250_DMA @@ -425,11 +439,10 @@ mtk8250_set_termios(struct uart_port *port, struct ktermios *termios, static int __maybe_unused mtk8250_runtime_suspend(struct device *dev) { struct mtk8250_data *data = dev_get_drvdata(dev); - struct uart_8250_port *up = serial8250_get_port(data->line); /* wait until UART in idle status */ while - (serial_in(up, MTK_UART_DEBUG0)); + (mtk8250_read(data, MTK_UART_DEBUG0)); if (data->clk_count == 0U) { dev_dbg(dev, "%s clock count is 0\n", __func__); @@ -553,6 +566,7 @@ static int mtk8250_probe(struct platform_device *pdev) if (!data) return -ENOMEM; + data->membase = uart.port.membase; data->clk_count = 0; if (pdev->dev.of_node) { @@ -570,7 +584,7 @@ static int mtk8250_probe(struct platform_device *pdev) uart.port.flags = UPF_BOOT_AUTOCONF | UPF_FIXED_PORT; uart.port.dev = &pdev->dev; uart.port.iotype = UPIO_MEM32; - uart.port.regshift = 2; + uart.port.regshift = MTK_UART_REGSHIFT; uart.port.private_data = data; uart.port.shutdown = mtk8250_shutdown; uart.port.startup = mtk8250_startup; @@ -581,27 +595,30 @@ static int mtk8250_probe(struct platform_device *pdev) uart.dma = data->dma; #endif - /* Disable Rate Fix function */ - writel(0x0, uart.port.membase + - (MTK_UART_RATE_FIX << uart.port.regshift)); - platform_set_drvdata(pdev, data); pm_runtime_enable(&pdev->dev); - err = mtk8250_runtime_resume(&pdev->dev); + err = pm_runtime_resume_and_get(&pdev->dev); if (err) goto err_pm_disable; + /* Disable Rate Fix function */ + mtk8250_write(data, 0, MTK_UART_RATE_FIX); + data->line = serial8250_register_8250_port(&uart); if (data->line < 0) { err = data->line; - goto err_pm_disable; + goto err_pm_put; } data->rx_wakeup_irq = platform_get_irq_optional(pdev, 1); + pm_runtime_put_sync(&pdev->dev); + return 0; +err_pm_put: + pm_runtime_put_sync(&pdev->dev); err_pm_disable: pm_runtime_disable(&pdev->dev); @@ -694,7 +711,7 @@ static int __init early_mtk8250_setup(struct earlycon_device *device, return -ENODEV; device->port.iotype = UPIO_MEM32; - device->port.regshift = 2; + device->port.regshift = MTK_UART_REGSHIFT; return early_serial8250_setup(device, NULL); }