> -----Original Message----- > From: Adrian Hunter [mailto:adrian.hunter@xxxxxxxxx] > Sent: Tuesday, November 30, 2010 6:54 PM > To: Tony Lindgren > Cc: Adrian Hunter; Manjunatha GK; Santosh Shilimkar; linux-omap Mailing > List > Subject: [PATCH 1/2] OMAP: DMA: prevent races while setting M idle mode to > nostandby > > 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> Acked-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx> > --- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
