linux-kernel - [PATCH 5.7 095/244] dmaengine: dw: Initialize channel before each transfer

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Date:   Mon, 20 Jul 2020 17:36:06 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Tsuchiya Yuto <kitakar@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vinod Koul <vkoul@...nel.org>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.7 095/244] dmaengine: dw: Initialize channel before each transfer

From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

[ Upstream commit 99ba8b9b0d9780e9937eb1d488d120e9e5c2533d ]

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")
Reported-by: Tsuchiya Yuto <kitakar@...il.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Acked-by: Viresh Kumar <viresh.kumar@...aro.org>
BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=206403
Link: https://lore.kernel.org/r/20200705115620.51929-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 21cb2a58dbd29..a1b56f52db2f2 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);
-- 
2.25.1