On Thu, Jan 10, 2013 at 02:07:05PM -0500, Matt Porter wrote:
> Implement device_channel_caps().
>
> EDMA has a finite set of PaRAM slots available for linking
> a multi-segment SG transfer. In order to prevent any one
> channel from consuming all PaRAM slots to fulfill a large SG
> transfer, the driver reports a static per-channel max number
> of SG segments it will handle.
>
> The maximum size of SG segment is limited by the slave config
> maxburst and addr_width for the channel in question. These values
> are used from the current channel config to calculate and return
> the max segment length cap.
>
> Signed-off-by: Matt Porter <mporter@xxxxxx>
> ---
> drivers/dma/edma.c | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
> index 82c8672..fc4b9db 100644
> --- a/drivers/dma/edma.c
> +++ b/drivers/dma/edma.c
> @@ -70,6 +70,7 @@ struct edma_chan {
> bool alloced;
> int slot[EDMA_MAX_SLOTS];
> struct dma_slave_config cfg;
> + struct dmaengine_chan_caps caps;
> };
>
> struct edma_cc {
> @@ -462,6 +463,28 @@ static void edma_issue_pending(struct dma_chan *chan)
> spin_unlock_irqrestore(&echan->vchan.lock, flags);
> }
>
> +static struct dmaengine_chan_caps
> +*edma_get_channel_caps(struct dma_chan *chan, enum dma_transfer_direction dir)
> +{
> + struct edma_chan *echan;
> + enum dma_slave_buswidth width = 0;
> + u32 burst = 0;
> +
> + if (chan) {
I think this check is redundant.
> + echan = to_edma_chan(chan);
> + if (dir == DMA_MEM_TO_DEV) {
> + width = echan->cfg.dst_addr_width;
> + burst = echan->cfg.dst_maxburst;
Per you API example burst and width is not set yet, so this doesn't make sense
> + } else if (dir == DMA_DEV_TO_MEM) {
> + width = echan->cfg.src_addr_width;
> + burst = echan->cfg.src_maxburst;
> + }
> + echan->caps.seg_len = (SZ_64K - 1) * width * burst;
Also the defination of API is max, above computation doesn't make sense to me!
--
~Vinod
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