dmaengine: stm32-dma: fix sleeping function called from invalid context (409ffc4d) · Commits · 戴 / test

This patch fixes BUG: sleeping function called from invalid context in stm32_dma_disable_chan function. The goal of this function is to force channel disable if it has not been disabled by hardware. This consists in clearing STM32_DMA_SCR_EN bit and read it as 0 to ensure the channel is well disabled and the last transfer is over. In previous implementation, the waiting loop was based on a do...while (1) with a call to cond_resched to give the scheduler a chance to run a higher priority process. But in some conditions, stm32_dma_disable_chan can be called while preemption is disabled, on a stm32_dma_stop call for example. So cond_resched must not be used. To avoid this, use readl_relaxed_poll_timeout_atomic to poll STM32_DMA_SCR_EN bit cleared. Signed-off-by:

Amelie Delaunay <amelie.delaunay@st.com> Link: https://lore.kernel.org/r/20200129153628.29329-8-amelie.delaunay@st.com Signed-off-by:

Vinod Koul <vkoul@kernel.org>

drivers/dma/stm32-dma.c

+9 −18

Original line number	Diff line number	Diff line
		@@ -15,6 +15,7 @@
		#include <linux/dma-mapping.h>
		#include <linux/err.h>
		#include <linux/init.h>
		#include <linux/iopoll.h>
		#include <linux/jiffies.h>
		#include <linux/list.h>
		#include <linux/module.h>
		@@ -421,29 +422,19 @@ static void stm32_dma_irq_clear(struct stm32_dma_chan *chan, u32 flags)
		static int stm32_dma_disable_chan(struct stm32_dma_chan *chan)
		{
		struct stm32_dma_device *dmadev = stm32_dma_get_dev(chan);
		unsigned long timeout = jiffies + msecs_to_jiffies(5000);
		u32 dma_scr, id;
		u32 dma_scr, id, reg;

		id = chan->id;
		dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));
		reg = STM32_DMA_SCR(id);
		dma_scr = stm32_dma_read(dmadev, reg);

		if (dma_scr & STM32_DMA_SCR_EN) {
		dma_scr &= ~STM32_DMA_SCR_EN;
		stm32_dma_write(dmadev, STM32_DMA_SCR(id), dma_scr);

		do {
		dma_scr = stm32_dma_read(dmadev, STM32_DMA_SCR(id));
		dma_scr &= STM32_DMA_SCR_EN;
		if (!dma_scr)
		break;
		stm32_dma_write(dmadev, reg, dma_scr);

		if (time_after_eq(jiffies, timeout)) {
		dev_err(chan2dev(chan), "%s: timeout!\n",
		__func__);
		return -EBUSY;
		}
		cond_resched();
		} while (1);
		return readl_relaxed_poll_timeout_atomic(dmadev->base + reg,
		dma_scr, !(dma_scr & STM32_DMA_SCR_EN),
		10, 1000000);
		}

		return 0;

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