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 X-Spam-Level: X-Spam-Status: No, score=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 526CEC11F6A for ; Thu, 1 Jul 2021 14:24:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 39138613C3 for ; Thu, 1 Jul 2021 14:24:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233977AbhGAO1L (ORCPT ); Thu, 1 Jul 2021 10:27:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60458 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233950AbhGAO1L (ORCPT ); Thu, 1 Jul 2021 10:27:11 -0400 Received: from mail-pj1-x1033.google.com (mail-pj1-x1033.google.com [IPv6:2607:f8b0:4864:20::1033]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF536C061762; Thu, 1 Jul 2021 07:24:40 -0700 (PDT) Received: by mail-pj1-x1033.google.com with SMTP id in17-20020a17090b4391b0290170ba0ec7fcso6732887pjb.4; Thu, 01 Jul 2021 07:24:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=mW1av2xdS1y2jG3ZVCe9a+vSXQ1T1E+gfBtuwxq5unk=; b=nvfJR6qQdw1paCfrrtoYPSZdPb8p2EjkJxnL4srGXcI6juBkHU6iUXG5h458hRWEIv 21lfzIuboj+UfJaHB2XKPmSay/KTTdCgHXKogF8/ChqCJw4YEt3JfcsyivGs+CGaLePz Gcj6NsTpOHJBZmHFMWtOymA8Wa7MSvn+8aG/8Eq6NXKxbjljMXGp4df0bcCRmYX3fO4K zV5x9ax1Wq0JoEbPOjxIkjCbxOivNEd727bhdiY6qXpHH/G0WrhL8A/4LpsTSUXuPfsz 18KFP2ABfTLduVpF2HPj5eiEhqVjWAvo14BcciV6S4kPqzd1pKC+jKhqDcfWL8IfTzul Lfkg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=mW1av2xdS1y2jG3ZVCe9a+vSXQ1T1E+gfBtuwxq5unk=; b=HvZR/OpuDGMwGeH3hHSFAQQhp4lVKzdLvWk7wC1gXQH2yu5lYbk/ZVO7cp8WbBoxSB +ADPVzocQWhH3fogetl8fVgT1wMVDGLy2z/2HvkhX/U59d/F4lFQDvNxQ4m3f2aJ0xzX gIKRJY0eN0zcAzTzcGfBGX4f0GcJ0VEKzqKDeOBKVlga0uMpZdvSe6L3xrz4CV3YnOQT rdamfHiFTQVpRQVvpZ2yq7KDk6TwHHJHrtxnRB9vJqFDkbzDzKNZQ2tk1BephzeP390W o4CdFF38ORaV7aFc1yStAmy8oWhZd+2YD/Dr0LZRuU7h2f57tNQReSojM2HhCGcxdam7 9nQQ== X-Gm-Message-State: AOAM533hhhOxSXF4cLeCFbX1nUEFHGHXZL/3LBlX8xSDO1bqSYmvpVKh ctBTxFDT67wGBIfkMSqEJCM= X-Google-Smtp-Source: ABdhPJwN8TK5iwZB8PkGLcVbcZBrAQy2hxo1r4BcZKhVigrizTzGD6K+OZwq5uWYe/dzjVShDlT/qg== X-Received: by 2002:a17:90a:3ccf:: with SMTP id k15mr28417657pjd.226.1625149480366; Thu, 01 Jul 2021 07:24:40 -0700 (PDT) Received: from sol (106-69-174-4.dyn.iinet.net.au. [106.69.174.4]) by smtp.gmail.com with ESMTPSA id t3sm204251pfl.44.2021.07.01.07.24.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 01 Jul 2021 07:24:39 -0700 (PDT) Date: Thu, 1 Jul 2021 22:24:33 +0800 From: Kent Gibson To: Dipen Patel Cc: thierry.reding@gmail.com, jonathanh@nvidia.com, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, linux-gpio@vger.kernel.org, linus.walleij@linaro.org, bgolaszewski@baylibre.com, devicetree@vger.kernel.org, linux-doc@vger.kernel.org, robh+dt@kernel.org Subject: Re: [RFC 08/11] gpiolib: cdev: Add hardware timestamp clock type Message-ID: <20210701142433.GC34285@sol> References: <20210625235532.19575-1-dipenp@nvidia.com> <20210625235532.19575-9-dipenp@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210625235532.19575-9-dipenp@nvidia.com> Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Fri, Jun 25, 2021 at 04:55:29PM -0700, Dipen Patel wrote: > This patch adds new clock type for the GPIO controller which can > timestamp gpio lines using hardware means. To expose such > functionalities to the userspace, code has been added in this patch > where during line create call, it checks for new clock type and if > requested, calls hardware timestamp related API from gpiolib.c. > During line change event, it retrieves timestamp in nano seconds by > calling gpiod_get_hw_timestamp API from gpiolib.c. At the line release, > it disables this functionality by calling gpiod_hw_timestamp_control. > > Signed-off-by: Dipen Patel > --- > drivers/gpio/gpiolib-cdev.c | 65 +++++++++++++++++++++++++++++++++++-- > include/uapi/linux/gpio.h | 1 + > 2 files changed, 64 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c > index 1631727bf0da..9f98c727e937 100644 > --- a/drivers/gpio/gpiolib-cdev.c > +++ b/drivers/gpio/gpiolib-cdev.c > @@ -518,6 +518,7 @@ struct linereq { > GPIO_V2_LINE_DRIVE_FLAGS | \ > GPIO_V2_LINE_EDGE_FLAGS | \ > GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME | \ > + GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE | \ > GPIO_V2_LINE_BIAS_FLAGS) > > static void linereq_put_event(struct linereq *lr, > @@ -540,9 +541,20 @@ static void linereq_put_event(struct linereq *lr, > > static u64 line_event_timestamp(struct line *line) > { > + bool block; > + > if (test_bit(FLAG_EVENT_CLOCK_REALTIME, &line->desc->flags)) > return ktime_get_real_ns(); > > + if (test_bit(FLAG_EVENT_CLOCK_HARDWARE, &line->desc->flags)) { > + if (irq_count()) > + block = false; > + else > + block = true; > + > + return gpiod_get_hw_timestamp(line->desc, block); > + } > + Use in_task() instead of block? > return ktime_get_ns(); > } > > @@ -828,6 +840,7 @@ static int edge_detector_setup(struct line *line, > return ret; > > line->irq = irq; > + > return 0; > } > Remove gratuitous whitespace changes. If you dislike the formatting then suggest it in a separate patch. > @@ -891,7 +904,6 @@ static int gpio_v2_line_flags_validate(u64 flags) > /* Return an error if an unknown flag is set */ > if (flags & ~GPIO_V2_LINE_VALID_FLAGS) > return -EINVAL; > - > /* > * Do not allow both INPUT and OUTPUT flags to be set as they are > * contradictory. > @@ -900,6 +912,14 @@ static int gpio_v2_line_flags_validate(u64 flags) > (flags & GPIO_V2_LINE_FLAG_OUTPUT)) > return -EINVAL; > Same here. > + /* > + * Do not mix with any other clocks if hardware assisted timestamp is > + * asked. > + */ > + if ((flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME) && > + (flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE)) > + return -EINVAL; > + The comment is very hw timestamp centric. It should just be something along the lines of "only allow one event clock source". > /* Edge detection requires explicit input. */ > if ((flags & GPIO_V2_LINE_EDGE_FLAGS) && > !(flags & GPIO_V2_LINE_FLAG_INPUT)) > @@ -992,6 +1012,8 @@ static void gpio_v2_line_config_flags_to_desc_flags(u64 flags, > > assign_bit(FLAG_EVENT_CLOCK_REALTIME, flagsp, > flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME); > + assign_bit(FLAG_EVENT_CLOCK_HARDWARE, flagsp, > + flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE); > } > > static long linereq_get_values(struct linereq *lr, void __user *ip) > @@ -1139,6 +1161,18 @@ static long linereq_set_config_unlocked(struct linereq *lr, > int val = gpio_v2_line_config_output_value(lc, i); > > edge_detector_stop(&lr->lines[i]); > + > + /* > + * Assuming line was input before and hardware > + * assisted timestamp only timestamps the input > + * lines. > + */ > + if (gpiod_is_hw_timestamp_enabled(desc)) { > + ret = gpiod_hw_timestamp_control(desc, false); > + if (ret) > + return ret; > + } > + So if you fail to disable the hw timestamp then you fail the set_config? Does that make sense? It should be impossible to fail, as per the preceding edge_detector_stop(), or any failure in this context is irrelevant and so can be ignored. > ret = gpiod_direction_output(desc, val); > if (ret) > return ret; > @@ -1152,6 +1186,13 @@ static long linereq_set_config_unlocked(struct linereq *lr, > polarity_change); > if (ret) > return ret; > + > + /* Check if new config sets hardware assisted clock */ > + if (flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE) { > + ret = gpiod_hw_timestamp_control(desc, true); > + if (ret) > + return ret; > + } > } > The error code here can come from the pinctrl timestamp_control(), so it should be sanitised before being returned to userspace. > blocking_notifier_call_chain(&desc->gdev->notifier, > @@ -1281,8 +1322,12 @@ static void linereq_free(struct linereq *lr) > > for (i = 0; i < lr->num_lines; i++) { > edge_detector_stop(&lr->lines[i]); > - if (lr->lines[i].desc) > + if (lr->lines[i].desc) { > + if (gpiod_is_hw_timestamp_enabled(lr->lines[i].desc)) > + gpiod_hw_timestamp_control(lr->lines[i].desc, > + false); > gpiod_free(lr->lines[i].desc); > + } Potential race on gpiod_is_hw_timestamp_enabled() and the call to gpiod_hw_timestamp_control()? Why not put the gpiod_is_hw_timestamp_enabled() check inside gpiod_hw_timestamp_control()? And the gpiod_hw_timestamp_control() call should be moved inside gpiod_free(), or more correctly gpiod_free_commit(). i.e. whenever you free the gpio you release any associated hw timestamp. > } > kfifo_free(&lr->events); > kfree(lr->label); > @@ -1409,6 +1454,15 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip) > flags & GPIO_V2_LINE_EDGE_FLAGS); > if (ret) > goto out_free_linereq; > + > + /* > + * Check if hardware assisted timestamp is requested > + */ > + if (flags & GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE) { > + ret = gpiod_hw_timestamp_control(desc, true); > + if (ret) > + goto out_free_linereq; > + } > } > Comment can fit on one line, and probably isn't even necessary - the code is clear enough. > blocking_notifier_call_chain(&desc->gdev->notifier, > @@ -1956,8 +2010,15 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc, > if (test_bit(FLAG_EDGE_FALLING, &desc->flags)) > info->flags |= GPIO_V2_LINE_FLAG_EDGE_FALLING; > > + /* > + * Practically it is possible that user will want both the real time > + * and hardware timestamps on GPIO events, for now however lets just > + * work with either clocks > + */ > if (test_bit(FLAG_EVENT_CLOCK_REALTIME, &desc->flags)) > info->flags |= GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME; > + else if (test_bit(FLAG_EVENT_CLOCK_HARDWARE, &desc->flags)) > + info->flags |= GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE; > If there is any need or intent to support multiple clock sources then avoid creeping API changes and add it now. Either way, drop the comment. > debounce_period_us = READ_ONCE(desc->debounce_period_us); > if (debounce_period_us) { > diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h > index eaaea3d8e6b4..d360545b4c21 100644 > --- a/include/uapi/linux/gpio.h > +++ b/include/uapi/linux/gpio.h > @@ -80,6 +80,7 @@ enum gpio_v2_line_flag { > GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN = _BITULL(9), > GPIO_V2_LINE_FLAG_BIAS_DISABLED = _BITULL(10), > GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME = _BITULL(11), > + GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE = _BITULL(12), > }; > > /** > -- > 2.17.1 > Cheers, Kent.