[PATCH v1] dmaengine: dw: Initialize channel before each transfer

[PATCH v1] dmaengine: dw: Initialize channel before each transfer

[Andy Shevchenko]

In some cases DMA can be used only with a consumer which does runtime power
management and on the platforms, that have DMA auto power gating logic
(see comments in the drivers/acpi/acpi_lpss.c), may result in DMA losing
its context. Simple mitigation of this issue is to initialize channel
each time the consumer initiates a transfer.

Fixes: cfdf5b6cc598 ("dw_dmac: add support for Lynxpoint DMA controllers")
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206403
Reported-by: Tsuchiya Yuto <kitakar@gmail.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/dma/dw/core.c | 12 ------------
 1 file changed, 12 deletions(-)

diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c
index 21cb2a58dbd2..a1b56f52db2f 100644
--- a/drivers/dma/dw/core.c
+++ b/drivers/dma/dw/core.c
@@ -118,16 +118,11 @@ static void dwc_initialize(struct dw_dma_chan *dwc)
 {
 	struct dw_dma *dw = to_dw_dma(dwc->chan.device);
 
-	if (test_bit(DW_DMA_IS_INITIALIZED, &dwc->flags))
-		return;
-
 	dw->initialize_chan(dwc);
 
 	/* Enable interrupts */
 	channel_set_bit(dw, MASK.XFER, dwc->mask);
 	channel_set_bit(dw, MASK.ERROR, dwc->mask);
-
-	set_bit(DW_DMA_IS_INITIALIZED, &dwc->flags);
 }
 
 /*----------------------------------------------------------------------*/
@@ -954,8 +949,6 @@ static void dwc_issue_pending(struct dma_chan *chan)
 
 void do_dw_dma_off(struct dw_dma *dw)
 {
-	unsigned int i;
-
 	dma_writel(dw, CFG, 0);
 
 	channel_clear_bit(dw, MASK.XFER, dw->all_chan_mask);
@@ -966,9 +959,6 @@ void do_dw_dma_off(struct dw_dma *dw)
 
 	while (dma_readl(dw, CFG) & DW_CFG_DMA_EN)
 		cpu_relax();
-
-	for (i = 0; i < dw->dma.chancnt; i++)
-		clear_bit(DW_DMA_IS_INITIALIZED, &dw->chan[i].flags);
 }
 
 void do_dw_dma_on(struct dw_dma *dw)
@@ -1032,8 +1022,6 @@ static void dwc_free_chan_resources(struct dma_chan *chan)
 	/* Clear custom channel configuration */
 	memset(&dwc->dws, 0, sizeof(struct dw_dma_slave));
 
-	clear_bit(DW_DMA_IS_INITIALIZED, &dwc->flags);
-
 	/* Disable interrupts */
 	channel_clear_bit(dw, MASK.XFER, dwc->mask);
 	channel_clear_bit(dw, MASK.BLOCK, dwc->mask);
-- 
2.27.0

Re: [PATCH v1] dmaengine: dw: Initialize channel before each transfer

[Viresh Kumar]

On 05-07-20, 14:56, Andy Shevchenko wrote:
> In some cases DMA can be used only with a consumer which does runtime power
> management and on the platforms, that have DMA auto power gating logic
> (see comments in the drivers/acpi/acpi_lpss.c), may result in DMA losing
> its context. Simple mitigation of this issue is to initialize channel
> each time the consumer initiates a transfer.
> 
> Fixes: cfdf5b6cc598 ("dw_dmac: add support for Lynxpoint DMA controllers")
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206403
> Reported-by: Tsuchiya Yuto <kitakar@gmail.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
>  drivers/dma/dw/core.c | 12 ------------
>  1 file changed, 12 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh

Re: [PATCH v1] dmaengine: dw: Initialize channel before each transfer

[Vinod Koul]

On 05-07-20, 14:56, Andy Shevchenko wrote:
> In some cases DMA can be used only with a consumer which does runtime power
> management and on the platforms, that have DMA auto power gating logic
> (see comments in the drivers/acpi/acpi_lpss.c), may result in DMA losing
> its context. Simple mitigation of this issue is to initialize channel
> each time the consumer initiates a transfer.

Applied, thanks

-- 
~Vinod