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dmaengine: tegra-apb: Improve DMA synchronization

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Boot CPU0 always handles DMA interrupts and under some rare circumstances
it could stuck in uninterruptible state for a significant time (like in a
case of KASAN + NFS root). In this case sibling CPU, which waits for DMA
transfer completion, will get a DMA transfer timeout. In order to handle
this rare condition, interrupt status needs to be polled until interrupt
is handled.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20200319212321.3297-2-digetx@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
This commit is contained in:
Dmitry Osipenko 2020-03-20 00:23:21 +03:00 committed by Vinod Koul
parent 6de88ea4ff
commit 6697255f23
1 changed files with 25 additions and 0 deletions
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25
drivers/dma/tegra20-apb-dma.c
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@ -24,6 +24,7 @@
#include <linux/pm_runtime.h>
#include <linux/reset.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include "dmaengine.h"
@ -202,6 +203,8 @@ struct tegra_dma_channel {
unsigned int slave_id;
struct dma_slave_config dma_sconfig;
struct tegra_dma_channel_regs channel_reg;
struct wait_queue_head wq;
};
/* tegra_dma: Tegra DMA specific information */
@ -680,6 +683,7 @@ static irqreturn_t tegra_dma_isr(int irq, void *dev_id)
tdc_write(tdc, TEGRA_APBDMA_CHAN_STATUS, status);
tdc->isr_handler(tdc, false);
tasklet_schedule(&tdc->tasklet);
wake_up_all(&tdc->wq);
spin_unlock(&tdc->lock);
return IRQ_HANDLED;
}
@ -785,6 +789,7 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
tegra_dma_resume(tdc);
pm_runtime_put(tdc->tdma->dev);
wake_up_all(&tdc->wq);
skip_dma_stop:
tegra_dma_abort_all(tdc);
@ -800,10 +805,29 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
return 0;
}
static bool tegra_dma_eoc_interrupt_deasserted(struct tegra_dma_channel *tdc)
{
unsigned long flags;
u32 status;
spin_lock_irqsave(&tdc->lock, flags);
status = tdc_read(tdc, TEGRA_APBDMA_CHAN_STATUS);
spin_unlock_irqrestore(&tdc->lock, flags);
return !(status & TEGRA_APBDMA_STATUS_ISE_EOC);
}
static void tegra_dma_synchronize(struct dma_chan *dc)
{
struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
/*
* CPU, which handles interrupt, could be busy in
* uninterruptible state, in this case sibling CPU
* should wait until interrupt is handled.
*/
wait_event(tdc->wq, tegra_dma_eoc_interrupt_deasserted(tdc));
tasklet_kill(&tdc->tasklet);
}
@ -1498,6 +1522,7 @@ static int tegra_dma_probe(struct platform_device *pdev)
tasklet_init(&tdc->tasklet, tegra_dma_tasklet,
(unsigned long)tdc);
spin_lock_init(&tdc->lock);
init_waitqueue_head(&tdc->wq);
INIT_LIST_HEAD(&tdc->pending_sg_req);
INIT_LIST_HEAD(&tdc->free_sg_req);