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Subject: Re: [PATCH] iio: adc: stm32: fix sleep inside atomic section when
 using DMA
To:     Fabrice Gasnier <fabrice.gasnier@st.com>, jic23@kernel.org
Cc:     lars@metafoo.de, alexandre.torgue@st.com,
        linux-iio@vger.kernel.org, pmeerw@pmeerw.net,
        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
References: <1553604244-10922-1-git-send-email-fabrice.gasnier@st.com>
From:   Mukesh Ojha <mojha@codeaurora.org>
Message-ID: <647777da-8077-6390-9778-08bef3d13074@codeaurora.org>
Date:   Wed, 27 Mar 2019 18:21:56 +0530
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On 3/26/2019 6:14 PM, Fabrice Gasnier wrote:
> Enabling CONFIG_DEBUG_ATOMIC_SLEEP=y triggers this BUG message:
> BUG: sleeping function called from invalid context at kernel/irq/chip.c...
>
> Call stack is as follows:
> - __might_sleep
> - handle_nested_irq          <-- Expects threaded irq
> - iio_trigger_poll_chained
> - stm32_adc_dma_buffer_done
> - vchan_complete
> - tasklet_action_common
> - tasklet_action
> - __do_softirq               <-- DMA completion raises a tasklet
> - irq_exit
> - __handle_domain_irq        <-- DMA IRQ
> - gic_handle_irq
>
> IIO expects threaded interrupt context when calling:
> - iio_trigger_poll_chained()
> Or it expects interrupt context when calling:
> - iio_trigger_poll()
>
> This patch triggers an IRQ upon stm32_adc_dma_buffer_done() DMA callback
> call, so the IIO trigger poll API gets called from IRQ context.
>
> Fixes: 2763ea0585c9 ("iio: adc: stm32: add optional dma support")
>
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>

Reviewed-by: Mukesh Ojha <mojha@codeaurora.org>

-Mukesh


> ---
>   drivers/iio/adc/Kconfig     |  1 +
>   drivers/iio/adc/stm32-adc.c | 32 ++++++++++++++++++++++++++++++--
>   2 files changed, 31 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 76db6e5..059407a 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -775,6 +775,7 @@ config STM32_ADC_CORE
>   	select MFD_STM32_TIMERS
>   	select IIO_STM32_TIMER_TRIGGER
>   	select IIO_TRIGGERED_BUFFER
> +	select IRQ_WORK
>   	help
>   	  Select this option to enable the core driver for STMicroelectronics
>   	  STM32 analog-to-digital converter (ADC).
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index 205e169..1aa3189 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -20,6 +20,7 @@
>   #include <linux/interrupt.h>
>   #include <linux/io.h>
>   #include <linux/iopoll.h>
> +#include <linux/irq_work.h>
>   #include <linux/module.h>
>   #include <linux/platform_device.h>
>   #include <linux/pm_runtime.h>
> @@ -297,6 +298,7 @@ struct stm32_adc_cfg {
>    * @smpr_val:		sampling time settings (e.g. smpr1 / smpr2)
>    * @cal:		optional calibration data on some devices
>    * @chan_name:		channel name array
> + * @work:		irq work used to call trigger poll routine
>    */
>   struct stm32_adc {
>   	struct stm32_adc_common	*common;
> @@ -320,6 +322,7 @@ struct stm32_adc {
>   	u32			smpr_val[2];
>   	struct stm32_adc_calib	cal;
>   	char			chan_name[STM32_ADC_CH_MAX][STM32_ADC_CH_SZ];
> +	struct irq_work		work;
>   };
>   
>   struct stm32_adc_diff_channel {
> @@ -1473,11 +1476,32 @@ static unsigned int stm32_adc_dma_residue(struct stm32_adc *adc)
>   	return 0;
>   }
>   
> +static void stm32_adc_dma_irq_work(struct irq_work *work)
> +{
> +	struct stm32_adc *adc = container_of(work, struct stm32_adc, work);
> +	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
> +
> +	/*
> +	 * iio_trigger_poll calls generic_handle_irq(). So, it requires hard
> +	 * irq context, and cannot be called directly from dma callback,
> +	 * dma cb has to schedule this work instead.
> +	 */
> +	iio_trigger_poll(indio_dev->trig);
> +}
> +
>   static void stm32_adc_dma_buffer_done(void *data)
>   {
>   	struct iio_dev *indio_dev = data;
> +	struct stm32_adc *adc = iio_priv(indio_dev);
>   
> -	iio_trigger_poll_chained(indio_dev->trig);
> +	/*
> +	 * Invoques iio_trigger_poll() from hard irq context: We can't
> +	 * call iio_trigger_poll() nor iio_trigger_poll_chained()
> +	 * directly from DMA callback (under tasklet e.g. softirq).
> +	 * They require respectively HW IRQ and threaded IRQ context
> +	 * as it might sleep.
> +	 */
> +	irq_work_queue(&adc->work);
>   }
>   
>   static int stm32_adc_dma_start(struct iio_dev *indio_dev)
> @@ -1585,8 +1609,10 @@ static void __stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
>   	if (!adc->dma_chan)
>   		stm32_adc_conv_irq_disable(adc);
>   
> -	if (adc->dma_chan)
> +	if (adc->dma_chan) {
>   		dmaengine_terminate_all(adc->dma_chan);
> +		irq_work_sync(&adc->work);
> +	}
>   
>   	if (stm32_adc_set_trig(indio_dev, NULL))
>   		dev_err(&indio_dev->dev, "Can't clear trigger\n");
> @@ -1872,6 +1898,8 @@ static int stm32_adc_dma_request(struct iio_dev *indio_dev)
>   	if (ret)
>   		goto err_free;
>   
> +	init_irq_work(&adc->work, stm32_adc_dma_irq_work);
> +
>   	return 0;
>   
>   err_free: