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Fri, 30 Jul 2021 02:16:36 +0000 Received: from [172.17.173.69] (172.20.187.6) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 30 Jul 2021 02:16:35 +0000 Subject: Re: [RFC 06/11] gpiolib: Add HTE support To: Kent Gibson CC: , , , , , , , , , References: <20210625235532.19575-1-dipenp@nvidia.com> <20210625235532.19575-7-dipenp@nvidia.com> <20210701142414.GB34285@sol> X-Nvconfidentiality: public From: Dipen Patel Message-ID: <5ed6ca9e-ee1e-23dd-5f2c-d674c74b3ea3@nvidia.com> Date: Thu, 29 Jul 2021 19:25:36 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210701142414.GB34285@sol> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [172.20.187.6] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL107.nvidia.com (172.20.187.13) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 7f7b0230-69da-4b1d-42ef-08d953000f42 X-MS-TrafficTypeDiagnostic: BN8PR12MB3220: X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:1148; 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X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Jul 2021 02:16:36.9762 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 7f7b0230-69da-4b1d-42ef-08d953000f42 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.112.34];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: CO1NAM11FT040.eop-nam11.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: BN8PR12MB3220 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/1/21 7:24 AM, Kent Gibson wrote: > On Fri, Jun 25, 2021 at 04:55:27PM -0700, Dipen Patel wrote: >> Some GPIO chip can provide hardware timestamp support on its GPIO lines >> , in order to support that additional functions needs to be added which >> can talk to both GPIO chip and HTE (hardware timestamping engine) >> subsystem. This patch introduces functions which gpio consumer can use >> to request hardware assisted timestamping. Below is the list of the APIs >> that are added in gpiolib subsystem. >> >> - gpiod_hw_timestamp_control - to enable/disable HTE on specified GPIO >> line. This API will return HTE specific descriptor for the specified >> GPIO line during the enable call, it will be stored as pointer in the >> gpio_desc structure as hw_ts_data. >> - gpiod_is_hw_timestamp_enabled - to query if HTE is enabled on >> specified GPIO line. >> - gpiod_get_hw_timestamp - to retrieve hardware timestamps. >> >> Signed-off-by: Dipen Patel >> --- >> drivers/gpio/gpiolib.c | 92 +++++++++++++++++++++++++++++++++++ >> drivers/gpio/gpiolib.h | 11 +++++ >> include/linux/gpio/consumer.h | 21 +++++++- >> include/linux/gpio/driver.h | 13 +++++ >> 4 files changed, 135 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c >> index 220a9d8dd4e3..335eaddfde98 100644 >> --- a/drivers/gpio/gpiolib.c >> +++ b/drivers/gpio/gpiolib.c >> @@ -2361,6 +2361,98 @@ int gpiod_direction_output(struct gpio_desc *desc, int value) >> } >> EXPORT_SYMBOL_GPL(gpiod_direction_output); >> >> +/** >> + * gpiod_hw_timestamp_control - set the hardware assisted timestamp control. >> + * @desc: GPIO to set >> + * @enable: Set true to enable the hardware timestamp, false otherwise. >> + * >> + * Certain GPIO chip can rely on hardware assisted timestamp engines which can >> + * record timestamp at the occurance of the configured events on selected GPIO >> + * lines. This is helper API to control such engine. >> + * >> + * Return 0 in case of success, else an error code. >> + */ >> +int gpiod_hw_timestamp_control(struct gpio_desc *desc, bool enable) >> +{ >> + struct gpio_chip *gc; >> + int ret = 0; >> + >> + VALIDATE_DESC(desc); >> + gc = desc->gdev->chip; >> + >> + if (!gc->timestamp_control) { >> + gpiod_warn(desc, >> + "%s: Hardware assisted ts not supported\n", >> + __func__); >> + return -ENOTSUPP; >> + } >> + >> + ret = gc->timestamp_control(gc, gpio_chip_hwgpio(desc), >> + &desc->hdesc, enable); >> + >> + if (ret) { >> + gpiod_warn(desc, >> + "%s: ts control operation failed\n", __func__); >> + return ret; >> + } >> + >> + if (!enable) >> + desc->hdesc = NULL; >> + >> + return ret; >> +} > Last I checked, pointer accesses are not guaranteed atomic, so how is > hdesc protected from concurrent access? > Here is it modified unprotected. > Below it is read unprotected. The assumption I made here was, gpiod_hw_timestamp_control will be called after client has made at least gpdio_request call. With that assumption, how two or more client/consumers call gpiod_hw_timestamp_control API with the same gpio_desc? I believe its not allowed as gpiod_request call will fail for the looser if there is a race and hence there will not be any race here in this API. Let me know your thoughts. > >> +EXPORT_SYMBOL_GPL(gpiod_hw_timestamp_control); >> + >> +/** >> + * gpiod_is_hw_timestamp_enabled - check if hardware assisted timestamp is >> + * enabled. >> + * @desc: GPIO to check >> + * >> + * Return true in case of success, false otherwise. >> + */ >> +bool gpiod_is_hw_timestamp_enabled(const struct gpio_desc *desc) >> +{ >> + if (!desc) >> + return false; >> + >> + return (desc->hdesc) ? true : false; >> +} >> +EXPORT_SYMBOL_GPL(gpiod_is_hw_timestamp_enabled); >> + >> +/** >> + * gpiod_get_hw_timestamp - Get hardware timestamp in nano seconds. >> + * @desc: GPIO to get the timestamp. >> + * @block: Set true to block until data is available. >> + * >> + * Return non-zero on success, else 0. >> + */ >> +u64 gpiod_get_hw_timestamp(struct gpio_desc *desc, bool block) >> +{ >> + struct gpio_chip *gc; >> + int ret = 0; >> + u64 ts; >> + >> + VALIDATE_DESC(desc); >> + gc = desc->gdev->chip; >> + >> + if (!gc->get_hw_timestamp) { >> + gpiod_warn(desc, >> + "%s: Hardware assisted ts not supported\n", >> + __func__); >> + return -ENOTSUPP; >> + } >> + > Can't return an error code here. Return value is u64, so this will look > like a valid ts. > > Just return 0 on error, as you do immediately below... yes, good catch. I forgot to clean that up. > >> + ret = gc->get_hw_timestamp(gc, block, desc->hdesc, &ts); >> + if (ret) { >> + gpiod_warn(desc, >> + "%s: get timestamp operation failed\n", __func__); >> + return 0; >> + } >> + >> + return ts; >> +} >> +EXPORT_SYMBOL_GPL(gpiod_get_hw_timestamp); >> + >> /** >> * gpiod_set_config - sets @config for a GPIO >> * @desc: descriptor of the GPIO for which to set the configuration >> diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h >> index 30bc3f80f83e..5393e1d90f61 100644 >> --- a/drivers/gpio/gpiolib.h >> +++ b/drivers/gpio/gpiolib.h >> @@ -15,6 +15,7 @@ >> #include >> #include >> #include >> +#include >> >> #define GPIOCHIP_NAME "gpiochip" >> >> @@ -117,6 +118,7 @@ struct gpio_desc { >> #define FLAG_EDGE_RISING 16 /* GPIO CDEV detects rising edge events */ >> #define FLAG_EDGE_FALLING 17 /* GPIO CDEV detects falling edge events */ >> #define FLAG_EVENT_CLOCK_REALTIME 18 /* GPIO CDEV reports REALTIME timestamps in events */ >> +#define FLAG_EVENT_CLOCK_HARDWARE 19 /* GPIO CDEV reports hardware timestamps in events */ >> >> /* Connection label */ >> const char *label; >> @@ -129,6 +131,15 @@ struct gpio_desc { >> /* debounce period in microseconds */ >> unsigned int debounce_period_us; >> #endif >> + /* >> + * Hardware timestamp engine related internal data structure. >> + * This gets set when the consumer calls gpiod_hw_timestamp_control to enable >> + * hardware timestamping on the specified GPIO line. The API calls into HTE >> + * subsystem, in turns HTE subsystem return the HTE descriptor for the GPIO >> + * line. The hdesc will be later used with gpiod_is_hw_timestamp_enabled >> + * and gpiod_get_hw_timestamp API calls. >> + */ >> + struct hte_ts_desc *hdesc; >> }; >> >> #define gpiod_not_found(desc) (IS_ERR(desc) && PTR_ERR(desc) == -ENOENT) >> diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h >> index c73b25bc9213..476ee04de7d0 100644 >> --- a/include/linux/gpio/consumer.h >> +++ b/include/linux/gpio/consumer.h >> @@ -112,6 +112,9 @@ int gpiod_get_direction(struct gpio_desc *desc); >> int gpiod_direction_input(struct gpio_desc *desc); >> int gpiod_direction_output(struct gpio_desc *desc, int value); >> int gpiod_direction_output_raw(struct gpio_desc *desc, int value); >> +int gpiod_hw_timestamp_control(struct gpio_desc *desc, bool enable); >> +bool gpiod_is_hw_timestamp_enabled(const struct gpio_desc *desc); >> +u64 gpiod_get_hw_timestamp(struct gpio_desc *desc, bool block); >> >> /* Value get/set from non-sleeping context */ >> int gpiod_get_value(const struct gpio_desc *desc); >> @@ -353,8 +356,22 @@ static inline int gpiod_direction_output_raw(struct gpio_desc *desc, int value) >> WARN_ON(desc); >> return -ENOSYS; >> } >> - >> - >> +static inline int gpiod_hw_timestamp_control(struct gpio_desc *desc, >> + bool enable) >> +{ >> + WARN_ON(desc); >> + return -ENOSYS; >> +} >> +static inline bool gpiod_is_hw_timestamp_enabled(const struct gpio_desc *desc) >> +{ >> + WARN_ON(desc); >> + return false; >> +} >> +static inline u64 gpiod_get_hw_timestamp(struct gpio_desc *desc, bool block) >> +{ >> + WARN_ON(desc); >> + return 0; >> +} >> static inline int gpiod_get_value(const struct gpio_desc *desc) >> { >> /* GPIO can never have been requested */ >> diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h >> index 3a268781fcec..f343e8f54b08 100644 >> --- a/include/linux/gpio/driver.h >> +++ b/include/linux/gpio/driver.h >> @@ -10,6 +10,7 @@ >> #include >> #include >> #include >> +#include /* For hardware timestamping */ >> >> struct gpio_desc; >> struct of_phandle_args; >> @@ -304,6 +305,10 @@ struct gpio_irq_chip { >> * @add_pin_ranges: optional routine to initialize pin ranges, to be used when >> * requires special mapping of the pins that provides GPIO functionality. >> * It is called after adding GPIO chip and before adding IRQ chip. >> + * @timestamp_control: Dependent on GPIO chip, an optional routine to >> + * enable/disable hardware assisted timestamp. >> + * @get_hw_timestamp: Retrieves hardware timestamp. The consumer can specify >> + * block parameter if it wishes to block till timestamp is available. >> * @base: identifies the first GPIO number handled by this chip; >> * or, if negative during registration, requests dynamic ID allocation. >> * DEPRECATION: providing anything non-negative and nailing the base >> @@ -396,6 +401,14 @@ struct gpio_chip { >> >> int (*add_pin_ranges)(struct gpio_chip *gc); >> >> + int (*timestamp_control)(struct gpio_chip *gc, >> + unsigned int offset, >> + struct hte_ts_desc **hdesc, >> + bool enable); >> + int (*get_hw_timestamp)(struct gpio_chip *gc, >> + bool block, >> + struct hte_ts_desc *hdesc, >> + u64 *ts); >> int base; >> u16 ngpio; >> const char *const *names; >> -- >> 2.17.1 >> > Cheers, > Kent.