[PATCH 5/5] dmaengine: pxa_dma: add support for legacy transition

Robert Jarzmik
2015-03-21T22:58:14Z

In order to achieve smooth transition of pxa drivers from old legacy dma
handling to new dmaengine, introduce a function to "hide" dma physical
channels from dmaengine.

This is temporary situation where pxa dma will be handled in 2 places :
- arch/arm/plat-pxa/dma.c
- drivers/dma/pxa_dma.c

The resources, ie. dma channels, will be controlled by pxa_dma. The
legacy code will request or release a channel with
pxad_toggle_reserved_channel().

This is not very pretty, but it ensures both legacy and dmaengine
consumers can live in the same kernel until the conversion is done.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
---
drivers/dma/pxa_dma.c | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)

diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c
index aec3e71..9b8ca68 100644
--- a/drivers/dma/pxa_dma.c
+++ b/drivers/dma/pxa_dma.c
@@ -417,6 +417,15 @@ static inline void pxad_init_debugfs(struct pxad_device *pdev) {}
static inline void pxad_cleanup_debugfs(struct pxad_device *pdev) {}
#endif

+/*
+ * In the transition phase where legacy pxa handling is done at the same time as
+ * mmp_dma, the DMA physical channel split between the 2 DMA providers is done
+ * through legacy_reserved. Legacy code reserves DMA channels by settings
+ * corresponding bits in legacy_reserved.
+ */
+static u32 legacy_reserved;
+static u32 legacy_unavailable;
+
static struct pxad_phy *lookup_phy(struct pxad_chan *pchan)
{
int prio, i;
@@ -437,10 +446,14 @@ static struct pxad_phy *lookup_phy(struct pxad_chan *pchan)
for (i = 0; i < pdev->nr_chans; i++) {
if (prio != (i & 0xf) >> 2)
continue;
+ if ((i < 32) && (legacy_reserved & BIT(i)))
+ continue;
phy = &pdev->phys[i];
if (!phy->vchan) {
phy->vchan = pchan;
found = phy;
+ if (i < 32)
+ legacy_unavailable |= BIT(i);
goto out_unlock;
}
}
@@ -458,6 +471,7 @@ static void pxad_free_phy(struct pxad_chan *chan)
struct pxad_device *pdev = to_pxad_dev(chan->vc.chan.device);
unsigned long flags;
u32 reg;
+ int i;

chan_dbg(chan, "freeing\n");
if (!chan->phy)
@@ -468,6 +482,9 @@ static void pxad_free_phy(struct pxad_chan *chan)
writel_relaxed(0, chan->phy->base + reg);

spin_lock_irqsave(&pdev->phy_lock, flags);
+ for (i = 0; i < 32; i++)
+ if (chan->phy == &pdev->phys[i])
+ legacy_unavailable &= ~BIT(i);
chan->phy->vchan = NULL;
chan->phy = NULL;
spin_unlock_irqrestore(&pdev->phy_lock, flags);
@@ -689,6 +706,8 @@ static irqreturn_t pxad_int_handler(int irq, void *dev_id)
i = __ffs(dint);
dint &= (dint - 1);
phy = &pdev->phys[i];
+ if ((i < 32) && (legacy_reserved & BIT(i)))
+ continue;
if (pxad_chan_handler(irq, phy) == IRQ_HANDLED)
ret = IRQ_HANDLED;
}
@@ -1440,6 +1459,15 @@ bool pxad_filter_fn(struct dma_chan *chan, void *param)
}
EXPORT_SYMBOL_GPL(pxad_filter_fn);

+int pxad_toggle_reserved_channel(int legacy_channel)
+{
+ if (legacy_unavailable & (BIT(legacy_channel)))
+ return -EBUSY;
+ legacy_reserved ^= BIT(legacy_channel);
+ return 0;
+}
+EXPORT_SYMBOL_GPL(pxad_toggle_reserved_channel);
+
module_platform_driver(pxad_driver);

MODULE_DESCRIPTION("Marvell PXA Peripheral DMA Driver");
--
2.1.4