From: Wolfram Sang <wsa+renesas@sang-engineering.com> To: linux-i2c@vger.kernel.org Cc: linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Peter Rosin <peda@axentia.se>, Stefan Lengfeld <contact@stefanchrist.eu>, linux-omap@vger.kernel.org, linux-tegra@vger.kernel.org, Linus Walleij <linus.walleij@linaro.org>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Wolfram Sang <wsa+renesas@sang-engineering.com> Subject: [PATCH 01/12] i2c: remove use of in_atomic() Date: Wed, 3 Apr 2019 14:40:08 +0200 [thread overview] Message-ID: <20190403124019.8947-2-wsa+renesas@sang-engineering.com> (raw) In-Reply-To: <20190403124019.8947-1-wsa+renesas@sang-engineering.com> Commit cea443a81c9c ("i2c: Support i2c_transfer in atomic contexts") added in_atomic() to the I2C core. However, the use of in_atomic() outside of core kernel code is discouraged and was already[1] when this code was added in early 2008. The above commit was a preparation for commit b7a3670131c7 ("i2c-pxa: Add polling transfer"). Its commit message says explicitly it was added "for cases where I2C transactions have to occur at times interrup[t]s are disabled". So, the intention was 'disabled interrupts'. This matches the use cases for atomic I2C transfers I have seen so far: very late communication (mostly to a PMIC) to powerdown or reboot the system. For those cases, interrupts are disabled then. It doesn't seem that in_atomic() adds value. After a discussion with Peter Zijlstra[2], we came up with a better set of conditionals to match the use case. The I2C core will soon gain an extra callback into bus drivers especially for atomic transfers to make them more generic. The code deciding which transfer to use (atomic/non-atomic) should mimic the behaviour which locking to use (trylock/lock). This is why we add a helper for it. [1] https://lwn.net/Articles/274695/ [2] http://patchwork.ozlabs.org/patch/1067437/ Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> --- drivers/i2c/i2c-core-base.c | 2 +- drivers/i2c/i2c-core.h | 10 ++++++++++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index 38af18645133..f8502064cd6b 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -1946,7 +1946,7 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) * one (discarding status on the second message) or errno * (discarding status on the first one). */ - if (in_atomic() || irqs_disabled()) { + if (i2c_in_atomic_xfer_mode()) { ret = i2c_trylock_bus(adap, I2C_LOCK_SEGMENT); if (!ret) /* I2C activity is ongoing. */ diff --git a/drivers/i2c/i2c-core.h b/drivers/i2c/i2c-core.h index 37576f50fe20..9d8526415b26 100644 --- a/drivers/i2c/i2c-core.h +++ b/drivers/i2c/i2c-core.h @@ -29,6 +29,16 @@ extern int __i2c_first_dynamic_bus_num; int i2c_check_7bit_addr_validity_strict(unsigned short addr); +/* + * We only allow atomic transfers for very late communication, e.g. to send + * the powerdown command to a PMIC. Atomic transfers are a corner case and not + * for generic use! + */ +static inline bool i2c_in_atomic_xfer_mode(void) +{ + return system_state > SYSTEM_RUNNING && irqs_disabled(); +} + #ifdef CONFIG_ACPI const struct acpi_device_id * i2c_acpi_match_device(const struct acpi_device_id *matches, -- 2.11.0
WARNING: multiple messages have this Message-ID (diff)
From: Wolfram Sang <wsa+renesas@sang-engineering.com> To: linux-i2c@vger.kernel.org Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Linus Walleij <linus.walleij@linaro.org>, linux-kernel@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Wolfram Sang <wsa+renesas@sang-engineering.com>, linux-tegra@vger.kernel.org, Stefan Lengfeld <contact@stefanchrist.eu>, linux-omap@vger.kernel.org, Peter Rosin <peda@axentia.se>, linux-arm-kernel@lists.infradead.org Subject: [PATCH 01/12] i2c: remove use of in_atomic() Date: Wed, 3 Apr 2019 14:40:08 +0200 [thread overview] Message-ID: <20190403124019.8947-2-wsa+renesas@sang-engineering.com> (raw) In-Reply-To: <20190403124019.8947-1-wsa+renesas@sang-engineering.com> Commit cea443a81c9c ("i2c: Support i2c_transfer in atomic contexts") added in_atomic() to the I2C core. However, the use of in_atomic() outside of core kernel code is discouraged and was already[1] when this code was added in early 2008. The above commit was a preparation for commit b7a3670131c7 ("i2c-pxa: Add polling transfer"). Its commit message says explicitly it was added "for cases where I2C transactions have to occur at times interrup[t]s are disabled". So, the intention was 'disabled interrupts'. This matches the use cases for atomic I2C transfers I have seen so far: very late communication (mostly to a PMIC) to powerdown or reboot the system. For those cases, interrupts are disabled then. It doesn't seem that in_atomic() adds value. After a discussion with Peter Zijlstra[2], we came up with a better set of conditionals to match the use case. The I2C core will soon gain an extra callback into bus drivers especially for atomic transfers to make them more generic. The code deciding which transfer to use (atomic/non-atomic) should mimic the behaviour which locking to use (trylock/lock). This is why we add a helper for it. [1] https://lwn.net/Articles/274695/ [2] http://patchwork.ozlabs.org/patch/1067437/ Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com> --- drivers/i2c/i2c-core-base.c | 2 +- drivers/i2c/i2c-core.h | 10 ++++++++++ 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index 38af18645133..f8502064cd6b 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -1946,7 +1946,7 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) * one (discarding status on the second message) or errno * (discarding status on the first one). */ - if (in_atomic() || irqs_disabled()) { + if (i2c_in_atomic_xfer_mode()) { ret = i2c_trylock_bus(adap, I2C_LOCK_SEGMENT); if (!ret) /* I2C activity is ongoing. */ diff --git a/drivers/i2c/i2c-core.h b/drivers/i2c/i2c-core.h index 37576f50fe20..9d8526415b26 100644 --- a/drivers/i2c/i2c-core.h +++ b/drivers/i2c/i2c-core.h @@ -29,6 +29,16 @@ extern int __i2c_first_dynamic_bus_num; int i2c_check_7bit_addr_validity_strict(unsigned short addr); +/* + * We only allow atomic transfers for very late communication, e.g. to send + * the powerdown command to a PMIC. Atomic transfers are a corner case and not + * for generic use! + */ +static inline bool i2c_in_atomic_xfer_mode(void) +{ + return system_state > SYSTEM_RUNNING && irqs_disabled(); +} + #ifdef CONFIG_ACPI const struct acpi_device_id * i2c_acpi_match_device(const struct acpi_device_id *matches, -- 2.11.0 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2019-04-03 12:40 UTC|newest] Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-04-03 12:40 [PATCH 00/12] i2c: core: introduce atomic transfers Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang [this message] 2019-04-03 12:40 ` [PATCH 01/12] i2c: remove use of in_atomic() Wolfram Sang 2019-04-15 12:40 ` Andy Shevchenko 2019-04-15 12:40 ` Andy Shevchenko 2019-04-15 21:55 ` Stefan Lengfeld 2019-04-15 21:55 ` Stefan Lengfeld 2019-04-15 21:55 ` Stefan Lengfeld 2019-04-16 10:48 ` Wolfram Sang 2019-04-16 10:48 ` Wolfram Sang 2019-04-03 12:40 ` [PATCH 02/12] i2c: core: use I2C locking behaviour also for SMBUS Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-15 12:39 ` Andy Shevchenko 2019-04-15 12:39 ` Andy Shevchenko 2019-04-15 12:39 ` Andy Shevchenko 2019-04-03 12:40 ` [PATCH 03/12] i2c: core: introduce callbacks for atomic transfers Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-15 12:39 ` Andy Shevchenko 2019-04-15 12:39 ` Andy Shevchenko 2019-04-15 21:57 ` Stefan Lengfeld 2019-04-15 21:57 ` Stefan Lengfeld 2019-04-03 12:40 ` [PATCH 04/12] i2c: mux: populate the new *_atomic callbacks Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-03 15:17 ` Peter Rosin 2019-04-03 15:17 ` Peter Rosin 2019-04-03 15:17 ` Peter Rosin 2019-04-15 12:04 ` Wolfram Sang 2019-04-15 12:04 ` Wolfram Sang 2019-04-15 12:04 ` Wolfram Sang 2019-04-15 12:44 ` Andy Shevchenko 2019-04-15 12:44 ` Andy Shevchenko 2019-04-03 12:40 ` [PATCH 05/12] i2c: demux: handle the new atomic callbacks Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-15 12:37 ` Andy Shevchenko 2019-04-15 12:37 ` Andy Shevchenko 2019-04-03 12:40 ` [PATCH 06/12] i2c: omap: Add the master_xfer_irqless hook Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-15 22:05 ` Stefan Lengfeld 2019-04-15 22:05 ` Stefan Lengfeld 2019-04-16 10:52 ` Wolfram Sang 2019-04-16 10:52 ` Wolfram Sang 2019-04-03 12:40 ` [PATCH 07/12] i2c: tegra-bpmp: convert to use new atomic callbacks Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-03 12:40 ` [PATCH 08/12] i2c: ocores: refactor setup for polling Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-05 15:09 ` Peter Korsgaard 2019-04-05 15:09 ` Peter Korsgaard 2019-04-05 19:00 ` Andrew Lunn 2019-04-05 19:00 ` Andrew Lunn 2019-04-03 12:40 ` [PATCH 09/12] i2c: ocores: enable atomic xfers Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-05 19:20 ` Andrew Lunn 2019-04-05 19:20 ` Andrew Lunn 2019-04-03 12:40 ` [PATCH 10/12] i2c: stu300: use xfer_atomic callback to bail out early Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-04 15:38 ` Linus Walleij 2019-04-04 15:38 ` Linus Walleij 2019-04-03 12:40 ` [PATCH 11/12] i2c: algo: bit: add flag to whitelist atomic transfers Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-03 12:40 ` [PATCH 12/12] i2c: gpio: flag atomic capability if possible Wolfram Sang 2019-04-03 12:40 ` Wolfram Sang 2019-04-04 15:40 ` Linus Walleij 2019-04-04 15:40 ` Linus Walleij 2019-04-15 12:38 ` Andy Shevchenko 2019-04-15 12:38 ` Andy Shevchenko 2019-04-03 13:15 ` [PATCH 00/12] i2c: core: introduce atomic transfers Andy Shevchenko 2019-04-03 13:15 ` Andy Shevchenko 2019-04-15 12:06 ` Wolfram Sang 2019-04-15 12:06 ` Wolfram Sang 2019-04-15 12:35 ` Andy Shevchenko 2019-04-15 12:35 ` Andy Shevchenko 2019-04-15 12:48 ` Andy Shevchenko 2019-04-15 12:48 ` Andy Shevchenko 2019-04-15 12:50 ` Wolfram Sang 2019-04-15 12:50 ` Wolfram Sang 2019-04-15 12:10 ` Wolfram Sang 2019-04-15 12:10 ` Wolfram Sang
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