diff options
| -rw-r--r-- | drivers/dma/bcm2835-dma.c | 92 |
1 files changed, 31 insertions, 61 deletions
diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c index 7beec403c2c9..ec8a291d62ba 100644 --- a/drivers/dma/bcm2835-dma.c +++ b/drivers/dma/bcm2835-dma.c @@ -2,9 +2,6 @@ /* * BCM2835 DMA engine support * - * This driver only supports cyclic DMA transfers - * as needed for the I2S module. - * * Author: Florian Meier <florian.meier@koalo.de> * Copyright 2013 * @@ -42,7 +39,6 @@ struct bcm2835_dmadev { struct dma_device ddev; - spinlock_t lock; void __iomem *base; struct device_dma_parameters dma_parms; }; @@ -64,7 +60,6 @@ struct bcm2835_cb_entry { struct bcm2835_chan { struct virt_dma_chan vc; - struct list_head node; struct dma_slave_config cfg; unsigned int dreq; @@ -405,39 +400,32 @@ static void bcm2835_dma_fill_cb_chain_with_sg( } } -static int bcm2835_dma_abort(void __iomem *chan_base) +static void bcm2835_dma_abort(struct bcm2835_chan *c) { - unsigned long cs; + void __iomem *chan_base = c->chan_base; long int timeout = 10000; - cs = readl(chan_base + BCM2835_DMA_CS); - if (!(cs & BCM2835_DMA_ACTIVE)) - return 0; + /* + * A zero control block address means the channel is idle. + * (The ACTIVE flag in the CS register is not a reliable indicator.) + */ + if (!readl(chan_base + BCM2835_DMA_ADDR)) + return; /* Write 0 to the active bit - Pause the DMA */ writel(0, chan_base + BCM2835_DMA_CS); /* Wait for any current AXI transfer to complete */ - while ((cs & BCM2835_DMA_ISPAUSED) && --timeout) { + while ((readl(chan_base + BCM2835_DMA_CS) & + BCM2835_DMA_WAITING_FOR_WRITES) && --timeout) cpu_relax(); - cs = readl(chan_base + BCM2835_DMA_CS); - } - /* We'll un-pause when we set of our next DMA */ + /* Peripheral might be stuck and fail to signal AXI write responses */ if (!timeout) - return -ETIMEDOUT; - - if (!(cs & BCM2835_DMA_ACTIVE)) - return 0; + dev_err(c->vc.chan.device->dev, + "failed to complete outstanding writes\n"); - /* Terminate the control block chain */ - writel(0, chan_base + BCM2835_DMA_NEXTCB); - - /* Abort the whole DMA */ - writel(BCM2835_DMA_ABORT | BCM2835_DMA_ACTIVE, - chan_base + BCM2835_DMA_CS); - - return 0; + writel(BCM2835_DMA_RESET, chan_base + BCM2835_DMA_CS); } static void bcm2835_dma_start_desc(struct bcm2835_chan *c) @@ -475,8 +463,15 @@ static irqreturn_t bcm2835_dma_callback(int irq, void *data) spin_lock_irqsave(&c->vc.lock, flags); - /* Acknowledge interrupt */ - writel(BCM2835_DMA_INT, c->chan_base + BCM2835_DMA_CS); + /* + * Clear the INT flag to receive further interrupts. Keep the channel + * active in case the descriptor is cyclic or in case the client has + * already terminated the descriptor and issued a new one. (May happen + * if this IRQ handler is threaded.) If the channel is finished, it + * will remain idle despite the ACTIVE flag being set. + */ + writel(BCM2835_DMA_INT | BCM2835_DMA_ACTIVE, + c->chan_base + BCM2835_DMA_CS); d = c->desc; @@ -484,11 +479,7 @@ static irqreturn_t bcm2835_dma_callback(int irq, void *data) if (d->cyclic) { /* call the cyclic callback */ vchan_cyclic_callback(&d->vd); - - /* Keep the DMA engine running */ - writel(BCM2835_DMA_ACTIVE, - c->chan_base + BCM2835_DMA_CS); - } else { + } else if (!readl(c->chan_base + BCM2835_DMA_ADDR)) { vchan_cookie_complete(&c->desc->vd); bcm2835_dma_start_desc(c); } @@ -506,8 +497,12 @@ static int bcm2835_dma_alloc_chan_resources(struct dma_chan *chan) dev_dbg(dev, "Allocating DMA channel %d\n", c->ch); + /* + * Control blocks are 256 bit in length and must start at a 256 bit + * (32 byte) aligned address (BCM2835 ARM Peripherals, sec. 4.2.1.1). + */ c->cb_pool = dma_pool_create(dev_name(dev), dev, - sizeof(struct bcm2835_dma_cb), 0, 0); + sizeof(struct bcm2835_dma_cb), 32, 0); if (!c->cb_pool) { dev_err(dev, "unable to allocate descriptor pool\n"); return -ENOMEM; @@ -776,39 +771,16 @@ static int bcm2835_dma_slave_config(struct dma_chan *chan, static int bcm2835_dma_terminate_all(struct dma_chan *chan) { struct bcm2835_chan *c = to_bcm2835_dma_chan(chan); - struct bcm2835_dmadev *d = to_bcm2835_dma_dev(c->vc.chan.device); unsigned long flags; - int timeout = 10000; LIST_HEAD(head); spin_lock_irqsave(&c->vc.lock, flags); - /* Prevent this channel being scheduled */ - spin_lock(&d->lock); - list_del_init(&c->node); - spin_unlock(&d->lock); - - /* - * Stop DMA activity: we assume the callback will not be called - * after bcm_dma_abort() returns (even if it does, it will see - * c->desc is NULL and exit.) - */ + /* stop DMA activity */ if (c->desc) { vchan_terminate_vdesc(&c->desc->vd); c->desc = NULL; - bcm2835_dma_abort(c->chan_base); - - /* Wait for stopping */ - while (--timeout) { - if (!(readl(c->chan_base + BCM2835_DMA_CS) & - BCM2835_DMA_ACTIVE)) - break; - - cpu_relax(); - } - - if (!timeout) - dev_err(d->ddev.dev, "DMA transfer could not be terminated\n"); + bcm2835_dma_abort(c); } vchan_get_all_descriptors(&c->vc, &head); @@ -836,7 +808,6 @@ static int bcm2835_dma_chan_init(struct bcm2835_dmadev *d, int chan_id, c->vc.desc_free = bcm2835_dma_desc_free; vchan_init(&c->vc, &d->ddev); - INIT_LIST_HEAD(&c->node); c->chan_base = BCM2835_DMA_CHANIO(d->base, chan_id); c->ch = chan_id; @@ -939,7 +910,6 @@ static int bcm2835_dma_probe(struct platform_device *pdev) od->ddev.residue_granularity = DMA_RESIDUE_GRANULARITY_BURST; od->ddev.dev = &pdev->dev; INIT_LIST_HEAD(&od->ddev.channels); - spin_lock_init(&od->lock); platform_set_drvdata(pdev, od); |