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Date: Sat, 21 Sep 2019 19:02:30 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Fabrice Gasnier <fabrice.gasnier@...com>
Cc: <linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <mcoquelin.stm32@...il.com>,
<alexandre.torgue@...com>, <linux-iio@...r.kernel.org>,
<lars@...afoo.de>, <knaack.h@....de>, <pmeerw@...erw.net>,
<linux-stm32@...md-mailman.stormreply.com>
Subject: Re: [PATCH v2 2/2] iio: adc: stm32-adc: fix a race when using
several adcs with dma and irq
On Tue, 17 Sep 2019 14:38:16 +0200
Fabrice Gasnier <fabrice.gasnier@...com> wrote:
> End of conversion may be handled by using IRQ or DMA. There may be a
> race when two conversions complete at the same time on several ADCs.
> EOC can be read as 'set' for several ADCs, with:
> - an ADC configured to use IRQs. EOCIE bit is set. The handler is normally
> called in this case.
> - an ADC configured to use DMA. EOCIE bit isn't set. EOC triggers the DMA
> request instead. It's then automatically cleared by DMA read. But the
> handler gets called due to status bit is temporarily set (IRQ triggered
> by the other ADC).
> So both EOC status bit in CSR and EOCIE control bit must be checked
> before invoking the interrupt handler (e.g. call ISR only for
> IRQ-enabled ADCs).
>
> Fixes: 2763ea0585c9 ("iio: adc: stm32: add optional dma support")
>
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@...com>
Both applied to the fixes-togreg branch of iio.git and marked for
stable.
Thanks,
Jonathan
> ---
> Changes in v2:
> - Keep registers definitions as a whole block to ease readability (add
> a precursor patch to move them to header file)
> ---
> drivers/iio/adc/stm32-adc-core.c | 43 +++++++++++++++++++++++++++++++++++++---
> drivers/iio/adc/stm32-adc-core.h | 1 +
> 2 files changed, 41 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c
> index 84ac326..93a096a 100644
> --- a/drivers/iio/adc/stm32-adc-core.c
> +++ b/drivers/iio/adc/stm32-adc-core.c
> @@ -44,6 +44,8 @@
> * @eoc1: adc1 end of conversion flag in @csr
> * @eoc2: adc2 end of conversion flag in @csr
> * @eoc3: adc3 end of conversion flag in @csr
> + * @ier: interrupt enable register offset for each adc
> + * @eocie_msk: end of conversion interrupt enable mask in @ier
> */
> struct stm32_adc_common_regs {
> u32 csr;
> @@ -51,6 +53,8 @@ struct stm32_adc_common_regs {
> u32 eoc1_msk;
> u32 eoc2_msk;
> u32 eoc3_msk;
> + u32 ier;
> + u32 eocie_msk;
> };
>
> struct stm32_adc_priv;
> @@ -276,6 +280,8 @@ static const struct stm32_adc_common_regs stm32f4_adc_common_regs = {
> .eoc1_msk = STM32F4_EOC1,
> .eoc2_msk = STM32F4_EOC2,
> .eoc3_msk = STM32F4_EOC3,
> + .ier = STM32F4_ADC_CR1,
> + .eocie_msk = STM32F4_EOCIE,
> };
>
> /* STM32H7 common registers definitions */
> @@ -284,8 +290,24 @@ static const struct stm32_adc_common_regs stm32h7_adc_common_regs = {
> .ccr = STM32H7_ADC_CCR,
> .eoc1_msk = STM32H7_EOC_MST,
> .eoc2_msk = STM32H7_EOC_SLV,
> + .ier = STM32H7_ADC_IER,
> + .eocie_msk = STM32H7_EOCIE,
> };
>
> +static const unsigned int stm32_adc_offset[STM32_ADC_MAX_ADCS] = {
> + 0, STM32_ADC_OFFSET, STM32_ADC_OFFSET * 2,
> +};
> +
> +static unsigned int stm32_adc_eoc_enabled(struct stm32_adc_priv *priv,
> + unsigned int adc)
> +{
> + u32 ier, offset = stm32_adc_offset[adc];
> +
> + ier = readl_relaxed(priv->common.base + offset + priv->cfg->regs->ier);
> +
> + return ier & priv->cfg->regs->eocie_msk;
> +}
> +
> /* ADC common interrupt for all instances */
> static void stm32_adc_irq_handler(struct irq_desc *desc)
> {
> @@ -296,13 +318,28 @@ static void stm32_adc_irq_handler(struct irq_desc *desc)
> chained_irq_enter(chip, desc);
> status = readl_relaxed(priv->common.base + priv->cfg->regs->csr);
>
> - if (status & priv->cfg->regs->eoc1_msk)
> + /*
> + * End of conversion may be handled by using IRQ or DMA. There may be a
> + * race here when two conversions complete at the same time on several
> + * ADCs. EOC may be read 'set' for several ADCs, with:
> + * - an ADC configured to use DMA (EOC triggers the DMA request, and
> + * is then automatically cleared by DR read in hardware)
> + * - an ADC configured to use IRQs (EOCIE bit is set. The handler must
> + * be called in this case)
> + * So both EOC status bit in CSR and EOCIE control bit must be checked
> + * before invoking the interrupt handler (e.g. call ISR only for
> + * IRQ-enabled ADCs).
> + */
> + if (status & priv->cfg->regs->eoc1_msk &&
> + stm32_adc_eoc_enabled(priv, 0))
> generic_handle_irq(irq_find_mapping(priv->domain, 0));
>
> - if (status & priv->cfg->regs->eoc2_msk)
> + if (status & priv->cfg->regs->eoc2_msk &&
> + stm32_adc_eoc_enabled(priv, 1))
> generic_handle_irq(irq_find_mapping(priv->domain, 1));
>
> - if (status & priv->cfg->regs->eoc3_msk)
> + if (status & priv->cfg->regs->eoc3_msk &&
> + stm32_adc_eoc_enabled(priv, 2))
> generic_handle_irq(irq_find_mapping(priv->domain, 2));
>
> chained_irq_exit(chip, desc);
> diff --git a/drivers/iio/adc/stm32-adc-core.h b/drivers/iio/adc/stm32-adc-core.h
> index 94aa2d2..2579d51 100644
> --- a/drivers/iio/adc/stm32-adc-core.h
> +++ b/drivers/iio/adc/stm32-adc-core.h
> @@ -25,6 +25,7 @@
> * --------------------------------------------------------
> */
> #define STM32_ADC_MAX_ADCS 3
> +#define STM32_ADC_OFFSET 0x100
> #define STM32_ADCX_COMN_OFFSET 0x300
>
> /* STM32F4 - Registers for each ADC instance */
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