diff options
author | Laxman Dewangan <ldewangan@nvidia.com> | 2012-01-09 21:05:11 +0100 |
---|---|---|
committer | Olof Johansson <olof@lixom.net> | 2012-02-07 03:24:59 +0100 |
commit | cb3732d0dc9df198c889a26210b6b27bc51a1c4a (patch) | |
tree | b95a5a952d14897c093d09af778dcafa39cf756e /arch/arm/mach-tegra | |
parent | ARM: tegra: emc: device tree support (diff) | |
download | linux-cb3732d0dc9df198c889a26210b6b27bc51a1c4a.tar.xz linux-cb3732d0dc9df198c889a26210b6b27bc51a1c4a.zip |
ARM: tegra: Pause DMA when reading transfer count
In order to read an accurate channel transfer count
from the APB DMA engine, the DMA controller must be
paused first.
Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>
Acked-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
Diffstat (limited to 'arch/arm/mach-tegra')
-rw-r--r-- | arch/arm/mach-tegra/dma.c | 116 |
1 files changed, 74 insertions, 42 deletions
diff --git a/arch/arm/mach-tegra/dma.c b/arch/arm/mach-tegra/dma.c index 122e46770d93..998c55ddca42 100644 --- a/arch/arm/mach-tegra/dma.c +++ b/arch/arm/mach-tegra/dma.c @@ -135,6 +135,7 @@ struct tegra_dma_channel { static bool tegra_dma_initialized; static DEFINE_MUTEX(tegra_dma_lock); +static DEFINE_SPINLOCK(enable_lock); static DECLARE_BITMAP(channel_usage, NV_DMA_MAX_CHANNELS); static struct tegra_dma_channel dma_channels[NV_DMA_MAX_CHANNELS]; @@ -200,18 +201,82 @@ static int tegra_dma_cancel(struct tegra_dma_channel *ch) return 0; } +static unsigned int get_channel_status(struct tegra_dma_channel *ch, + struct tegra_dma_req *req, bool is_stop_dma) +{ + void __iomem *addr = IO_ADDRESS(TEGRA_APB_DMA_BASE); + unsigned int status; + + if (is_stop_dma) { + /* + * STOP the DMA and get the transfer count. + * Getting the transfer count is tricky. + * - Globally disable DMA on all channels + * - Read the channel's status register to know the number + * of pending bytes to be transfered. + * - Stop the dma channel + * - Globally re-enable DMA to resume other transfers + */ + spin_lock(&enable_lock); + writel(0, addr + APB_DMA_GEN); + udelay(20); + status = readl(ch->addr + APB_DMA_CHAN_STA); + tegra_dma_stop(ch); + writel(GEN_ENABLE, addr + APB_DMA_GEN); + spin_unlock(&enable_lock); + if (status & STA_ISE_EOC) { + pr_err("Got Dma Int here clearing"); + writel(status, ch->addr + APB_DMA_CHAN_STA); + } + req->status = TEGRA_DMA_REQ_ERROR_ABORTED; + } else { + status = readl(ch->addr + APB_DMA_CHAN_STA); + } + return status; +} + +/* should be called with the channel lock held */ +static unsigned int dma_active_count(struct tegra_dma_channel *ch, + struct tegra_dma_req *req, unsigned int status) +{ + unsigned int to_transfer; + unsigned int req_transfer_count; + unsigned int bytes_transferred; + + to_transfer = ((status & STA_COUNT_MASK) >> STA_COUNT_SHIFT) + 1; + req_transfer_count = ch->req_transfer_count + 1; + bytes_transferred = req_transfer_count; + if (status & STA_BUSY) + bytes_transferred -= to_transfer; + /* + * In continuous transfer mode, DMA only tracks the count of the + * half DMA buffer. So, if the DMA already finished half the DMA + * then add the half buffer to the completed count. + */ + if (ch->mode & TEGRA_DMA_MODE_CONTINOUS) { + if (req->buffer_status == TEGRA_DMA_REQ_BUF_STATUS_HALF_FULL) + bytes_transferred += req_transfer_count; + if (status & STA_ISE_EOC) + bytes_transferred += req_transfer_count; + } + bytes_transferred *= 4; + return bytes_transferred; +} + int tegra_dma_dequeue_req(struct tegra_dma_channel *ch, struct tegra_dma_req *_req) { - unsigned int csr; unsigned int status; struct tegra_dma_req *req = NULL; int found = 0; unsigned long irq_flags; - int to_transfer; - int req_transfer_count; + int stop = 0; spin_lock_irqsave(&ch->lock, irq_flags); + + if (list_entry(ch->list.next, struct tegra_dma_req, node) == _req) + stop = 1; + list_for_each_entry(req, &ch->list, node) { if (req == _req) { list_del(&req->node); @@ -224,47 +289,12 @@ int tegra_dma_dequeue_req(struct tegra_dma_channel *ch, return 0; } - /* STOP the DMA and get the transfer count. - * Getting the transfer count is tricky. - * - Change the source selector to invalid to stop the DMA from - * FIFO to memory. - * - Read the status register to know the number of pending - * bytes to be transferred. - * - Finally stop or program the DMA to the next buffer in the - * list. - */ - csr = readl(ch->addr + APB_DMA_CHAN_CSR); - csr &= ~CSR_REQ_SEL_MASK; - csr |= CSR_REQ_SEL_INVALID; - writel(csr, ch->addr + APB_DMA_CHAN_CSR); - - /* Get the transfer count */ - status = readl(ch->addr + APB_DMA_CHAN_STA); - to_transfer = (status & STA_COUNT_MASK) >> STA_COUNT_SHIFT; - req_transfer_count = ch->req_transfer_count; - req_transfer_count += 1; - to_transfer += 1; + if (!stop) + goto skip_stop_dma; - req->bytes_transferred = req_transfer_count; + status = get_channel_status(ch, req, true); + req->bytes_transferred = dma_active_count(ch, req, status); - if (status & STA_BUSY) - req->bytes_transferred -= to_transfer; - - /* In continuous transfer mode, DMA only tracks the count of the - * half DMA buffer. So, if the DMA already finished half the DMA - * then add the half buffer to the completed count. - * - * FIXME: There can be a race here. What if the req to - * dequue happens at the same time as the DMA just moved to - * the new buffer and SW didn't yet received the interrupt? - */ - if (ch->mode & TEGRA_DMA_MODE_CONTINOUS) - if (req->buffer_status == TEGRA_DMA_REQ_BUF_STATUS_HALF_FULL) - req->bytes_transferred += req_transfer_count; - - req->bytes_transferred *= 4; - - tegra_dma_stop(ch); if (!list_empty(&ch->list)) { /* if the list is not empty, queue the next request */ struct tegra_dma_req *next_req; @@ -272,6 +302,8 @@ int tegra_dma_dequeue_req(struct tegra_dma_channel *ch, typeof(*next_req), node); tegra_dma_update_hw(ch, next_req); } + +skip_stop_dma: req->status = -TEGRA_DMA_REQ_ERROR_ABORTED; spin_unlock_irqrestore(&ch->lock, irq_flags); |