From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from bh-25.webhostbox.net ([208.91.199.152]:58688 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751130AbcE0NtJ (ORCPT ); Fri, 27 May 2016 09:49:09 -0400 Subject: Re: [RFC PATCH 1/3] watchdog: Add Meson GXBB Watchdog Driver To: Neil Armstrong , Wim Van Sebroeck References: <1464249112-13658-1-git-send-email-narmstrong@baylibre.com> <1464249112-13658-2-git-send-email-narmstrong@baylibre.com> <57470026.3000501@roeck-us.net> <57480470.4000708@baylibre.com> Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-watchdog@vger.kernel.org From: Guenter Roeck Message-ID: <57485045.70707@roeck-us.net> Date: Fri, 27 May 2016 06:48:53 -0700 MIME-Version: 1.0 In-Reply-To: <57480470.4000708@baylibre.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-watchdog-owner@vger.kernel.org List-Id: linux-watchdog@vger.kernel.org On 05/27/2016 01:25 AM, Neil Armstrong wrote: [ ... ] >>> + data->wdt_dev.max_hw_heartbeat_ms = GXBB_WDT_TCNT_SETUP_MASK; >>> + data->wdt_dev.min_hw_heartbeat_ms = 1; >> >> Does the device require a minimum time between heartbeats ? >> Just asking, because you violate it yourself below. >> >> If you want to set the minimum timeout, that would be min_timeout. > > Ok, these values are not very clear actually. > Hmmm .. yes, reading the description again, it doesn't really describe well what it is doing. Essentially, min_hw_heartbeat_ms is enforced by the watchdog core, and should be used if a watchdog hardware can not tolerate short intervals between heartbeats. min_timeout is the minimum timeout value configurable from user space. >>> + data->wdt_dev.timeout = DEFAULT_TIMEOUT; >>> + watchdog_set_drvdata(&data->wdt_dev, data); >>> + >>> + watchdog_init_timeout(&data->wdt_dev, DEFAULT_TIMEOUT, &pdev->dev); >>> + >> >> DEFAULT_TIMEOUT is unnecessary here. Since the default timeout is already set, >> it makes the call useless. >> >>> + ret = watchdog_register_device(&data->wdt_dev); >>> + if (ret) >>> + return ret; >>> + >>> + /* Setup with 1ms timebase */ >>> + writel(((clk_get_rate(data->clk) / 1000) & GXBB_WDT_CTRL_DIV_MASK) | >>> + GXBB_WDT_CTRL_EE_RESET | >>> + GXBB_WDT_CTRL_CLK_EN | >>> + GXBB_WDT_CTRL_CLKDIV_EN, >>> + data->reg_base + GXBB_WDT_CTRL_REG); >>> + meson_gxbb_wdt_set_timeout(&data->wdt_dev, data->wdt_dev.timeout); >> >> set_timeout already calls the ping function. Also, the functions should be called >> prior to watchdog registration to avoid race conditions. >> >>> + meson_gxbb_wdt_ping(&data->wdt_dev); >> >> This is unusual. If the watchdog can be already running, it might make sense >> to tell the core about it (set WDOG_HW_RUNNING in the status field), so it >> can send heartbeats until user space opens the device. > > Yes, since meson_gxbb_wdt_set_timeout() already ping, this is useless. > Not only that - if the watchdog _is_ already running at boot time, you should really set WDOG_HW_RUNNING to let the watchdog core know. You status function would come handy there. if (meson_gxbb_wdt_status(data)) // note the changed parameter set_bit(WDOG_HW_RUNNING, &data->wdt_dev.status); Thanks, Guenter