>From 8c0f4490d93b67326ff24f6ce1c7e925b08d96b3 Mon Sep 17 00:00:00 2001
From: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Date: Mon, 22 Nov 2010 11:32:48 +0200
Subject: [PATCH 1/2] OMAP: DMA: prevent races while setting M idle mode to nostandby
In a couple of OMAP errata cases, sDMA M idle mode must be
set temporarily to nostandby. If two DMA users were to do
that at the same time, a race condition would arise.
Prevent that by using a spin lock and counting up/down the
number of times nostandby is set/reset.
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
arch/arm/plat-omap/dma.c | 59 ++++++++++++++++++++++++++++++++++-----------
1 files changed, 44 insertions(+), 15 deletions(-)
diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c
index a863f55..6158c99 100644
--- a/arch/arm/plat-omap/dma.c
+++ b/arch/arm/plat-omap/dma.c
@@ -139,6 +139,9 @@ static spinlock_t dma_chan_lock;
static struct omap_dma_lch *dma_chan;
static void __iomem *omap_dma_base;
+static u32 midlemode_saved;
+static int midlemode_save_cnt;
+
static const u8 omap1_dma_irq[OMAP1_LOGICAL_DMA_CH_COUNT] = {
INT_DMA_CH0_6, INT_DMA_CH1_7, INT_DMA_CH2_8, INT_DMA_CH3,
INT_DMA_CH4, INT_DMA_CH5, INT_1610_DMA_CH6, INT_1610_DMA_CH7,
@@ -1016,6 +1019,41 @@ void omap_start_dma(int lch)
}
EXPORT_SYMBOL(omap_start_dma);
+static void midlemode_nostandby(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&dma_chan_lock, flags);
+ if (!midlemode_save_cnt) {
+ u32 l;
+
+ midlemode_saved = dma_read(OCP_SYSCONFIG);
+ l = midlemode_saved;
+ l &= ~DMA_SYSCONFIG_MIDLEMODE_MASK;
+ l |= DMA_SYSCONFIG_MIDLEMODE(DMA_IDLEMODE_NO_IDLE);
+ dma_write(l, OCP_SYSCONFIG);
+ }
+ midlemode_save_cnt += 1;
+ spin_unlock_irqrestore(&dma_chan_lock, flags);
+}
+
+static void midlemode_restore(void)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&dma_chan_lock, flags);
+ midlemode_save_cnt -= 1;
+ if (!midlemode_save_cnt) {
+ u32 l;
+
+ l = dma_read(OCP_SYSCONFIG);
+ l &= ~DMA_SYSCONFIG_MIDLEMODE_MASK;
+ l |= midlemode_saved & DMA_SYSCONFIG_MIDLEMODE_MASK;
+ dma_write(l, OCP_SYSCONFIG);
+ }
+ spin_unlock_irqrestore(&dma_chan_lock, flags);
+}
+
void omap_stop_dma(int lch)
{
u32 l;
@@ -1028,16 +1066,10 @@ void omap_stop_dma(int lch)
/* OMAP3 Errata i541: sDMA FIFO draining does not finish */
if (cpu_is_omap34xx() && (l & OMAP_DMA_CCR_SEL_SRC_DST_SYNC)) {
int i = 0;
- u32 sys_cf;
/* Configure No-Standby */
- l = dma_read(OCP_SYSCONFIG);
- sys_cf = l;
- l &= ~DMA_SYSCONFIG_MIDLEMODE_MASK;
- l |= DMA_SYSCONFIG_MIDLEMODE(DMA_IDLEMODE_NO_IDLE);
- dma_write(l , OCP_SYSCONFIG);
+ midlemode_nostandby();
- l = dma_read(CCR(lch));
l &= ~OMAP_DMA_CCR_EN;
dma_write(l, CCR(lch));
@@ -1053,7 +1085,7 @@ void omap_stop_dma(int lch)
printk(KERN_ERR "DMA drain did not complete on "
"lch %d\n", lch);
/* Restore OCP_SYSCONFIG */
- dma_write(sys_cf, OCP_SYSCONFIG);
+ midlemode_restore();
} else {
l &= ~OMAP_DMA_CCR_EN;
dma_write(l, CCR(lch));
@@ -1711,7 +1743,6 @@ int omap_stop_dma_chain_transfers(int chain_id)
{
int *channels;
u32 l, i;
- u32 sys_cf;
/* Check for input params */
if (unlikely((chain_id < 0 || chain_id >= dma_lch_count))) {
@@ -1730,11 +1761,9 @@ int omap_stop_dma_chain_transfers(int chain_id)
* DMA Errata:
* Special programming model needed to disable DMA before end of block
*/
- sys_cf = dma_read(OCP_SYSCONFIG);
- l = sys_cf;
- /* Middle mode reg set no Standby */
- l &= ~((1 << 12)|(1 << 13));
- dma_write(l, OCP_SYSCONFIG);
+
+ /* M idle mode reg set no Standby */
+ midlemode_nostandby();
for (i = 0; i < dma_linked_lch[chain_id].no_of_lchs_linked; i++) {
@@ -1754,7 +1783,7 @@ int omap_stop_dma_chain_transfers(int chain_id)
OMAP_DMA_CHAIN_QINIT(chain_id);
/* Errata - put in the old value */
- dma_write(sys_cf, OCP_SYSCONFIG);
+ midlemode_restore();
return 0;
}
--
1.7.0.4
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