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Message-ID: <20130705064449.GC10947@intel.com>
Date: Fri, 5 Jul 2013 12:14:49 +0530
From: Vinod Koul <vinod.koul@...el.com>
To: Xiang Wang <wangxfdu@...il.com>
Cc: Dan Williams <djbw@...com>, linux-kernel@...r.kernel.org,
cxie4@...vell.com, Xiang Wang <wangx@...vell.com>
Subject: Re: [PATCH V2] dma: mmp_pdma: support for getting residual bytes
On Tue, Jun 18, 2013 at 04:41:20PM +0800, Xiang Wang wrote:
> From: Xiang Wang <wangx@...vell.com>
>
> In some of our drivers (e.g. UART) we may stop a running DMA
> before it finishes. So we need APIs to know how many bytes
> have been transferred.
>
> Signed-off-by: Xiang Wang <wangx@...vell.com>
> ---
> drivers/dma/mmp_pdma.c | 88 +++++++++++++++++++++++++++++++++++++++++++----
> 1 files changed, 80 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/dma/mmp_pdma.c b/drivers/dma/mmp_pdma.c
> index c26699f..57cd047 100644
> --- a/drivers/dma/mmp_pdma.c
> +++ b/drivers/dma/mmp_pdma.c
> @@ -104,7 +104,8 @@ struct mmp_pdma_chan {
> spinlock_t desc_lock; /* Descriptor list lock */
> struct list_head chain_pending; /* Link descriptors queue for pending */
> struct list_head chain_running; /* Link descriptors queue for running */
> - bool idle; /* channel statue machine */
> + enum dma_status status; /* channel status machine */
> + u32 bytes_residue;
>
> struct dma_pool *desc_pool; /* Descriptors pool */
> };
> @@ -270,7 +271,7 @@ static void start_pending_queue(struct mmp_pdma_chan *chan)
> struct mmp_pdma_desc_sw *desc;
>
> /* still in running, irq will start the pending list */
> - if (!chan->idle) {
> + if (chan->status == DMA_IN_PROGRESS) {
> dev_dbg(chan->dev, "DMA controller still busy\n");
> return;
> }
> @@ -307,7 +308,64 @@ static void start_pending_queue(struct mmp_pdma_chan *chan)
> */
> set_desc(chan->phy, desc->async_tx.phys);
> enable_chan(chan->phy);
> - chan->idle = false;
> + chan->status = DMA_IN_PROGRESS;
> + chan->bytes_residue = 0;
> +}
> +
> +/*
> + * Get the number of pending bytes. Should be called with desc_lock held
> + * because we are accessing desc list.
> + */
> +static u32 mmp_pdma_get_bytes_residue(struct mmp_pdma_chan *chan)
> +{
> + u32 reg, orig_pos, cur_pos, ddadr, residue = 0;
> + bool running_desc_found = false;
> + struct mmp_pdma_desc_sw *desc_sw;
> +
> + /*
> + * When a phy channel is unavailable, maybe it has been freed, return
> + * last stored value for safe.
> + */
> + if (!chan->phy)
> + return chan->bytes_residue;
> +
> + reg = (chan->phy->idx << 4) + DDADR;
> + ddadr = readl_relaxed(chan->phy->base + reg);
> +
> + /* iterate over all descriptors to sum up the number of pending bytes */
and why?
Residue does not mean sum of all pending bytes across all descriptors submitted
You need to find the residue of current descriptor only and return
> + list_for_each_entry(desc_sw, &chan->chain_running, node) {
> + /* for the case of a running descriptor */
> + if (desc_sw->desc.ddadr == ddadr && !running_desc_found) {
> + switch (chan->dir) {
> + case DMA_DEV_TO_MEM:
> + case DMA_MEM_TO_MEM:
> + reg = (chan->phy->idx << 4) + DTADR;
> + cur_pos = readl_relaxed(chan->phy->base + reg);
> + orig_pos = desc_sw->desc.dtadr;
> + break;
> +
> + case DMA_MEM_TO_DEV:
> + reg = (chan->phy->idx << 4) + DSADR;
> + cur_pos = readl_relaxed(chan->phy->base + reg);
> + orig_pos = desc_sw->desc.dsadr;
> + break;
> +
> + default:
> + cur_pos = 0;
> + orig_pos = 0;
This makes no sense...
> + }
> + residue = (u32)(desc_sw->desc.dcmd & DCMD_LENGTH)
> + + orig_pos - cur_pos;
> + running_desc_found = true;
> + continue;
> + }
> +
> + /* for the case of following un-started descriptors*/
> + if (running_desc_found)
> + residue += (u32)(desc_sw->desc.dcmd & DCMD_LENGTH);
> + }
> +
> + return residue;
> }
>
>
> @@ -381,7 +439,7 @@ static int mmp_pdma_alloc_chan_resources(struct dma_chan *dchan)
> chan->phy->vchan = NULL;
> chan->phy = NULL;
> }
> - chan->idle = true;
> + chan->status = DMA_SUCCESS;
> chan->dev_addr = 0;
> return 1;
> }
> @@ -409,7 +467,7 @@ static void mmp_pdma_free_chan_resources(struct dma_chan *dchan)
>
> dma_pool_destroy(chan->desc_pool);
> chan->desc_pool = NULL;
> - chan->idle = true;
> + chan->status = DMA_SUCCESS;
> chan->dev_addr = 0;
> if (chan->phy) {
> chan->phy->vchan = NULL;
> @@ -588,9 +646,16 @@ static int mmp_pdma_control(struct dma_chan *dchan, enum dma_ctrl_cmd cmd,
> spin_lock_irqsave(&chan->desc_lock, flags);
> mmp_pdma_free_desc_list(chan, &chan->chain_pending);
> mmp_pdma_free_desc_list(chan, &chan->chain_running);
> + chan->bytes_residue = 0;
> spin_unlock_irqrestore(&chan->desc_lock, flags);
> - chan->idle = true;
> + chan->status = DMA_SUCCESS;
> break;
> +
> + case DMA_PAUSE:
> + disable_chan(chan->phy);
> + chan->status = DMA_PAUSED;
> + break;
this should be a separate patch
--
~Vinod
--
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