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Subject[PATCH v2 4/5] dmaengine: plx-dma: Implement hardware initialization and cleanup
Allocate DMA coherent memory for the ring of DMA descriptors and
program the appropriate hardware registers.

A tasklet is created which is triggered on an interrupt to process
all the finished requests. Additionally, any remaining descriptors
are aborted when the hardware is removed or the resources freed.

Use an RCU pointer to synchronize PCI device unbind.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
drivers/dma/plx_dma.c | 344 +++++++++++++++++++++++++++++++++++++++++-
1 file changed, 343 insertions(+), 1 deletion(-)

diff --git a/drivers/dma/plx_dma.c b/drivers/dma/plx_dma.c
index 54e13cb92d51..d3c2319e2fad 100644
--- a/drivers/dma/plx_dma.c
+++ b/drivers/dma/plx_dma.c
@@ -18,13 +18,103 @@ MODULE_VERSION("0.1");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Logan Gunthorpe");

+#define PLX_REG_DESC_RING_ADDR 0x214
+#define PLX_REG_DESC_RING_ADDR_HI 0x218
+#define PLX_REG_DESC_RING_NEXT_ADDR 0x21C
+#define PLX_REG_DESC_RING_COUNT 0x220
+#define PLX_REG_DESC_RING_LAST_ADDR 0x224
+#define PLX_REG_DESC_RING_LAST_SIZE 0x228
+#define PLX_REG_PREF_LIMIT 0x234
+#define PLX_REG_CTRL 0x238
+#define PLX_REG_CTRL2 0x23A
+#define PLX_REG_INTR_CTRL 0x23C
+#define PLX_REG_INTR_STATUS 0x23E
+
+#define PLX_REG_PREF_LIMIT_PREF_FOUR 8
+
+#define PLX_REG_CTRL_GRACEFUL_PAUSE BIT(0)
+#define PLX_REG_CTRL_ABORT BIT(1)
+#define PLX_REG_CTRL_WRITE_BACK_EN BIT(2)
+#define PLX_REG_CTRL_START BIT(3)
+#define PLX_REG_CTRL_RING_STOP_MODE BIT(4)
+#define PLX_REG_CTRL_DESC_MODE_BLOCK (0 << 5)
+#define PLX_REG_CTRL_DESC_MODE_ON_CHIP (1 << 5)
+#define PLX_REG_CTRL_DESC_MODE_OFF_CHIP (2 << 5)
+#define PLX_REG_CTRL_DESC_INVALID BIT(8)
+#define PLX_REG_CTRL_GRACEFUL_PAUSE_DONE BIT(9)
+#define PLX_REG_CTRL_ABORT_DONE BIT(10)
+#define PLX_REG_CTRL_IMM_PAUSE_DONE BIT(12)
+#define PLX_REG_CTRL_IN_PROGRESS BIT(30)
+
+#define PLX_REG_CTRL_RESET_VAL (PLX_REG_CTRL_DESC_INVALID | \
+ PLX_REG_CTRL_GRACEFUL_PAUSE_DONE | \
+ PLX_REG_CTRL_ABORT_DONE | \
+ PLX_REG_CTRL_IMM_PAUSE_DONE)
+
+#define PLX_REG_CTRL_START_VAL (PLX_REG_CTRL_WRITE_BACK_EN | \
+ PLX_REG_CTRL_DESC_MODE_OFF_CHIP | \
+ PLX_REG_CTRL_START | \
+ PLX_REG_CTRL_RESET_VAL)
+
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_64B 0
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_128B 1
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_256B 2
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_512B 3
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_1KB 4
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_2KB 5
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_4B 7
+
+#define PLX_REG_INTR_CRTL_ERROR_EN BIT(0)
+#define PLX_REG_INTR_CRTL_INV_DESC_EN BIT(1)
+#define PLX_REG_INTR_CRTL_ABORT_DONE_EN BIT(3)
+#define PLX_REG_INTR_CRTL_PAUSE_DONE_EN BIT(4)
+#define PLX_REG_INTR_CRTL_IMM_PAUSE_DONE_EN BIT(5)
+
+#define PLX_REG_INTR_STATUS_ERROR BIT(0)
+#define PLX_REG_INTR_STATUS_INV_DESC BIT(1)
+#define PLX_REG_INTR_STATUS_DESC_DONE BIT(2)
+#define PLX_REG_INTR_CRTL_ABORT_DONE BIT(3)
+
+struct plx_dma_hw_std_desc {
+ __le32 flags_and_size;
+ __le16 dst_addr_hi;
+ __le16 src_addr_hi;
+ __le32 dst_addr_lo;
+ __le32 src_addr_lo;
+};
+
+#define PLX_DESC_SIZE_MASK 0x7ffffff
+#define PLX_DESC_FLAG_VALID BIT(31)
+#define PLX_DESC_FLAG_INT_WHEN_DONE BIT(30)
+
+#define PLX_DESC_WB_SUCCESS BIT(30)
+#define PLX_DESC_WB_RD_FAIL BIT(29)
+#define PLX_DESC_WB_WR_FAIL BIT(28)
+
+#define PLX_DMA_RING_COUNT 2048
+
+struct plx_dma_desc {
+ struct dma_async_tx_descriptor txd;
+ struct plx_dma_hw_std_desc *hw;
+ u32 orig_size;
+};
+
struct plx_dma_dev {
struct dma_device dma_dev;
struct dma_chan dma_chan;
+ struct pci_dev __rcu *pdev;
void __iomem *bar;

struct kref ref;
struct work_struct release_work;
+ struct tasklet_struct desc_task;
+
+ spinlock_t ring_lock;
+ bool ring_active;
+ int head;
+ int tail;
+ struct plx_dma_hw_std_desc *hw_ring;
+ struct plx_dma_desc **desc_ring;
};

static struct plx_dma_dev *chan_to_plx_dma_dev(struct dma_chan *c)
@@ -32,6 +122,146 @@ static struct plx_dma_dev *chan_to_plx_dma_dev(struct dma_chan *c)
return container_of(c, struct plx_dma_dev, dma_chan);
}

+static struct plx_dma_desc *plx_dma_get_desc(struct plx_dma_dev *plxdev, int i)
+{
+ return plxdev->desc_ring[i & (PLX_DMA_RING_COUNT - 1)];
+}
+
+static void plx_dma_process_desc(struct plx_dma_dev *plxdev)
+{
+ struct dmaengine_result res;
+ struct plx_dma_desc *desc;
+ u32 flags;
+
+ spin_lock_bh(&plxdev->ring_lock);
+
+ while (plxdev->tail != plxdev->head) {
+ desc = plx_dma_get_desc(plxdev, plxdev->tail);
+
+ flags = le32_to_cpu(READ_ONCE(desc->hw->flags_and_size));
+
+ if (flags & PLX_DESC_FLAG_VALID)
+ break;
+
+ res.residue = desc->orig_size - (flags & PLX_DESC_SIZE_MASK);
+
+ if (flags & PLX_DESC_WB_SUCCESS)
+ res.result = DMA_TRANS_NOERROR;
+ else if (flags & PLX_DESC_WB_WR_FAIL)
+ res.result = DMA_TRANS_WRITE_FAILED;
+ else
+ res.result = DMA_TRANS_READ_FAILED;
+
+ dma_cookie_complete(&desc->txd);
+ dma_descriptor_unmap(&desc->txd);
+ dmaengine_desc_get_callback_invoke(&desc->txd, &res);
+ desc->txd.callback = NULL;
+ desc->txd.callback_result = NULL;
+
+ plxdev->tail++;
+ }
+
+ spin_unlock_bh(&plxdev->ring_lock);
+}
+
+static void plx_dma_abort_desc(struct plx_dma_dev *plxdev)
+{
+ struct dmaengine_result res;
+ struct plx_dma_desc *desc;
+
+ plx_dma_process_desc(plxdev);
+
+ spin_lock_bh(&plxdev->ring_lock);
+
+ while (plxdev->tail != plxdev->head) {
+ desc = plx_dma_get_desc(plxdev, plxdev->tail);
+
+ res.residue = desc->orig_size;
+ res.result = DMA_TRANS_ABORTED;
+
+ dma_cookie_complete(&desc->txd);
+ dma_descriptor_unmap(&desc->txd);
+ dmaengine_desc_get_callback_invoke(&desc->txd, &res);
+ desc->txd.callback = NULL;
+ desc->txd.callback_result = NULL;
+
+ plxdev->tail++;
+ }
+
+ spin_unlock_bh(&plxdev->ring_lock);
+}
+
+static void __plx_dma_stop(struct plx_dma_dev *plxdev)
+{
+ unsigned long timeout = jiffies + msecs_to_jiffies(1000);
+ u32 val;
+
+ val = readl(plxdev->bar + PLX_REG_CTRL);
+ if (!(val & ~PLX_REG_CTRL_GRACEFUL_PAUSE))
+ return;
+
+ writel(PLX_REG_CTRL_RESET_VAL | PLX_REG_CTRL_GRACEFUL_PAUSE,
+ plxdev->bar + PLX_REG_CTRL);
+
+ while (!time_after(jiffies, timeout)) {
+ val = readl(plxdev->bar + PLX_REG_CTRL);
+ if (val & PLX_REG_CTRL_GRACEFUL_PAUSE_DONE)
+ break;
+
+ cpu_relax();
+ }
+
+ if (!(val & PLX_REG_CTRL_GRACEFUL_PAUSE_DONE))
+ dev_err(plxdev->dma_dev.dev,
+ "Timeout waiting for graceful pause!\n");
+
+ writel(PLX_REG_CTRL_RESET_VAL | PLX_REG_CTRL_GRACEFUL_PAUSE,
+ plxdev->bar + PLX_REG_CTRL);
+
+ writel(0, plxdev->bar + PLX_REG_DESC_RING_COUNT);
+ writel(0, plxdev->bar + PLX_REG_DESC_RING_ADDR);
+ writel(0, plxdev->bar + PLX_REG_DESC_RING_ADDR_HI);
+ writel(0, plxdev->bar + PLX_REG_DESC_RING_NEXT_ADDR);
+}
+
+static void plx_dma_stop(struct plx_dma_dev *plxdev)
+{
+ rcu_read_lock();
+ if (!rcu_dereference(plxdev->pdev)) {
+ rcu_read_unlock();
+ return;
+ }
+
+ __plx_dma_stop(plxdev);
+
+ rcu_read_unlock();
+}
+
+static void plx_dma_desc_task(unsigned long data)
+{
+ struct plx_dma_dev *plxdev = (void *)data;
+
+ plx_dma_process_desc(plxdev);
+}
+
+static irqreturn_t plx_dma_isr(int irq, void *devid)
+{
+ struct plx_dma_dev *plxdev = devid;
+ u32 status;
+
+ status = readw(plxdev->bar + PLX_REG_INTR_STATUS);
+
+ if (!status)
+ return IRQ_NONE;
+
+ if (status & PLX_REG_INTR_STATUS_DESC_DONE && plxdev->ring_active)
+ tasklet_schedule(&plxdev->desc_task);
+
+ writew(status, plxdev->bar + PLX_REG_INTR_STATUS);
+
+ return IRQ_HANDLED;
+}
+
static void plx_dma_release_work(struct work_struct *work)
{
struct plx_dma_dev *plxdev = container_of(work, struct plx_dma_dev,
@@ -61,18 +291,109 @@ static void plx_dma_put(struct plx_dma_dev *plxdev)
kref_put(&plxdev->ref, plx_dma_release);
}

+static int plx_dma_alloc_desc(struct plx_dma_dev *plxdev)
+{
+ struct plx_dma_desc *desc;
+ int i;
+
+ plxdev->desc_ring = kcalloc(PLX_DMA_RING_COUNT,
+ sizeof(*plxdev->desc_ring), GFP_KERNEL);
+ if (!plxdev->desc_ring)
+ return -ENOMEM;
+
+ for (i = 0; i < PLX_DMA_RING_COUNT; i++) {
+ desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+ if (!desc)
+ goto free_and_exit;
+
+ dma_async_tx_descriptor_init(&desc->txd, &plxdev->dma_chan);
+ desc->hw = &plxdev->hw_ring[i];
+ plxdev->desc_ring[i] = desc;
+ }
+
+ return 0;
+
+free_and_exit:
+ for (i = 0; i < PLX_DMA_RING_COUNT; i++)
+ kfree(plxdev->desc_ring[i]);
+ kfree(plxdev->desc_ring);
+ return -ENOMEM;
+}
+
static int plx_dma_alloc_chan_resources(struct dma_chan *chan)
{
struct plx_dma_dev *plxdev = chan_to_plx_dma_dev(chan);
+ size_t ring_sz = PLX_DMA_RING_COUNT * sizeof(*plxdev->hw_ring);
+ dma_addr_t dma_addr;
+ int rc;
+
+ rcu_read_lock();
+ if (!rcu_dereference(plxdev->pdev)) {
+ rcu_read_unlock();
+ return -ENODEV;
+ }

kref_get(&plxdev->ref);

- return 0;
+ writel(PLX_REG_CTRL_RESET_VAL, plxdev->bar + PLX_REG_CTRL);
+
+ plxdev->hw_ring = dmam_alloc_coherent(plxdev->dma_dev.dev, ring_sz,
+ &dma_addr, GFP_KERNEL);
+ if (!plxdev->hw_ring) {
+ rcu_read_unlock();
+ return -ENOMEM;
+ }
+
+ plxdev->head = plxdev->tail = 0;
+
+ rc = plx_dma_alloc_desc(plxdev);
+ if (rc) {
+ plx_dma_put(plxdev);
+ rcu_read_unlock();
+ return rc;
+ }
+
+ writel(lower_32_bits(dma_addr), plxdev->bar + PLX_REG_DESC_RING_ADDR);
+ writel(upper_32_bits(dma_addr),
+ plxdev->bar + PLX_REG_DESC_RING_ADDR_HI);
+ writel(lower_32_bits(dma_addr),
+ plxdev->bar + PLX_REG_DESC_RING_NEXT_ADDR);
+ writel(PLX_DMA_RING_COUNT, plxdev->bar + PLX_REG_DESC_RING_COUNT);
+ writel(PLX_REG_PREF_LIMIT_PREF_FOUR, plxdev->bar + PLX_REG_PREF_LIMIT);
+
+ plxdev->ring_active = true;
+
+ rcu_read_unlock();
+
+ return PLX_DMA_RING_COUNT;
}

static void plx_dma_free_chan_resources(struct dma_chan *chan)
{
struct plx_dma_dev *plxdev = chan_to_plx_dma_dev(chan);
+ struct pci_dev *pdev;
+ int i;
+
+ spin_lock_bh(&plxdev->ring_lock);
+ plxdev->ring_active = false;
+ spin_unlock_bh(&plxdev->ring_lock);
+
+ plx_dma_stop(plxdev);
+
+ rcu_read_lock();
+ pdev = rcu_dereference(plxdev->pdev);
+ if (pdev)
+ synchronize_irq(pci_irq_vector(pdev, 0));
+ rcu_read_unlock();
+
+ tasklet_kill(&plxdev->desc_task);
+
+ plx_dma_abort_desc(plxdev);
+
+ for (i = 0; i < PLX_DMA_RING_COUNT; i++)
+ kfree(plxdev->desc_ring[i]);
+
+ kfree(plxdev->desc_ring);

plx_dma_put(plxdev);
}
@@ -88,9 +409,20 @@ static int plx_dma_create(struct pci_dev *pdev)
if (!plxdev)
return -ENOMEM;

+ rc = request_irq(pci_irq_vector(pdev, 0), plx_dma_isr, 0,
+ KBUILD_MODNAME, plxdev);
+ if (rc) {
+ kfree(plxdev);
+ return rc;
+ }
+
kref_init(&plxdev->ref);
INIT_WORK(&plxdev->release_work, plx_dma_release_work);
+ spin_lock_init(&plxdev->ring_lock);
+ tasklet_init(&plxdev->desc_task, plx_dma_desc_task,
+ (unsigned long)plxdev);

+ RCU_INIT_POINTER(plxdev->pdev, pdev);
plxdev->bar = pcim_iomap_table(pdev)[0];

dma = &plxdev->dma_dev;
@@ -169,6 +501,16 @@ static void plx_dma_remove(struct pci_dev *pdev)

free_irq(pci_irq_vector(pdev, 0), plxdev);

+ rcu_assign_pointer(plxdev->pdev, NULL);
+ synchronize_rcu();
+
+ spin_lock_bh(&plxdev->ring_lock);
+ plxdev->ring_active = false;
+ spin_unlock_bh(&plxdev->ring_lock);
+
+ __plx_dma_stop(plxdev);
+ plx_dma_abort_desc(plxdev);
+
plxdev->bar = NULL;
plx_dma_put(plxdev);

--
2.20.1
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