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Wysocki" References: <1579854369-7972-1-git-send-email-fabrice.gasnier@st.com> <20200202153354.3dae5863@archlinux> From: Fabrice Gasnier Message-ID: Date: Wed, 12 Feb 2020 15:02:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20200202153354.3dae5863@archlinux> Content-Language: en-US X-Originating-IP: [10.75.127.45] X-ClientProxiedBy: SFHDAG6NODE2.st.com (10.75.127.17) To SFHDAG5NODE3.st.com (10.75.127.15) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.572 definitions=2020-02-12_07:2020-02-11, 2020-02-12 signatures=0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200212_060248_178354_6D278E70 X-CRM114-Status: GOOD ( 21.66 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ulf.hansson@linaro.org, lars@metafoo.de, olivier.moysan@st.com, alexandre.torgue@st.com, linux-pm@vger.kernel.org, linux-iio@vger.kernel.org, pmeerw@pmeerw.net, khilman@kernel.org, linux-kernel@vger.kernel.org, mcoquelin.stm32@gmail.com, knaack.h@gmx.de, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2/2/20 4:33 PM, Jonathan Cameron wrote: > On Fri, 24 Jan 2020 09:26:09 +0100 > Fabrice Gasnier wrote: > >> When the ADC is runtime suspended and starting a conversion, the stm32-adc >> driver calls pm_runtime_get_sync() that gets cascaded to the parent >> (e.g. runtime resume of stm32-adc-core driver). This also kicks the >> autosuspend delay (e.g. 2s) of the parent. >> Once the ADC is active, calling pm_runtime_get_sync() again (upon a new >> capture) won't kick the autosuspend delay for the parent (stm32-adc-core >> driver) as already active. >> >> Currently, this makes the stm32-adc-core driver go in suspend state >> every 2s when doing slow polling. As an example, doing a capture, e.g. >> cat in_voltageY_raw at a 0.2s rate, the auto suspend delay for the parent >> isn't refreshed. Once it expires, the parent immediately falls into >> runtime suspended state, in between two captures, as soon as the child >> driver falls into runtime suspend state: >> - e.g. after 2s, + child calls pm_runtime_put_autosuspend() + 100ms >> autosuspend delay of the child. >> - stm32-adc-core switches off regulators, clocks and so on. >> - They get switched on back again 100ms later in this example (at 2.2s). >> >> So, add an explicit call to pm_runtime_mark_last_busy() for the parent >> driver (stm32-adc-core), synchronously with the child driver (stm32-adc), >> to avoid this. >> >> Fixes: 9bdbb1139ca1 ("iio: adc: stm32-adc: add power management support") >> >> Signed-off-by: Fabrice Gasnier > > Hi Fabrice, > > Whilst this will clearly work, it seems like a somewhat adhoc solution. > Power management specialists (cc'd): Is this what we should be doing, or > have Fabrice and I both missed something that we should be doing here? Hi all, PM specialists, As per my understanding, pm_runtime_mark_last_busy() doesn't cascade to the parent device: - in pm_runtime.h: static inline void pm_runtime_mark_last_busy(struct device *dev) { WRITE_ONCE(dev->power.last_busy, ktime_get_mono_fast_ns()); } STM32 ADC driver uses a model with an autosupsend delay for - a parent driver to handle common resources, registers etc. - child drivers for each ADC. So the question is on how to fix the behavior I described: 1: Child activity with "short" autosuspend_delay 2: Parent activity with "longer" autosuspend_delay _ _ _ _ _ _ _ _ 1: _| |___| |___| |___| |___| |_..._| |___| |___| |_... v v v v v v v v v v ... v v v v v v | | | | | +- pm_runtime_mark_last_busy() | | | +- pm_runtime_put_autosuspend() v | | | | +--- pm_runtime_get_sync() | v | | | +---> expires after autosuspend_delay | | | | | v v v _______________________________________ ___... 2: _| ... |___| Glitches on parent dev near autosuspend_delay ^ - does the child driver needs to "kick" parent driver with pm_runtime_mark_last_busy(), as proposed in current patch ? - or is it something that should be done by PM runtime core routines ? e.g. make pm_runtime_mark_last_busy() recursive or something else ? Please advise Best regards, Fabrice > > Thanks, > > Jonathan > >> --- >> drivers/iio/adc/stm32-adc.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c >> index 3b291d7..670157e 100644 >> --- a/drivers/iio/adc/stm32-adc.c >> +++ b/drivers/iio/adc/stm32-adc.c >> @@ -1157,6 +1157,7 @@ static int stm32_adc_single_conv(struct iio_dev *indio_dev, >> >> stm32_adc_conv_irq_disable(adc); >> >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> >> @@ -1278,6 +1279,7 @@ static int stm32_adc_update_scan_mode(struct iio_dev *indio_dev, >> adc->num_conv = bitmap_weight(scan_mask, indio_dev->masklength); >> >> ret = stm32_adc_conf_scan_seq(indio_dev, scan_mask); >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> >> @@ -1329,6 +1331,7 @@ static int stm32_adc_debugfs_reg_access(struct iio_dev *indio_dev, >> else >> *readval = stm32_adc_readl(adc, reg); >> >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> >> @@ -1451,6 +1454,7 @@ static int __stm32_adc_buffer_postenable(struct iio_dev *indio_dev) >> err_clr_trig: >> stm32_adc_set_trig(indio_dev, NULL); >> err_pm_put: >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> >> @@ -1487,6 +1491,7 @@ static void __stm32_adc_buffer_predisable(struct iio_dev *indio_dev) >> if (stm32_adc_set_trig(indio_dev, NULL)) >> dev_err(&indio_dev->dev, "Can't clear trigger\n"); >> >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> } >> @@ -1874,6 +1879,7 @@ static int stm32_adc_probe(struct platform_device *pdev) >> goto err_hw_stop; >> } >> >> + pm_runtime_mark_last_busy(dev->parent); >> pm_runtime_mark_last_busy(dev); >> pm_runtime_put_autosuspend(dev); >> > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel