On 05/06/2014 03:22 PM, Christopher Freeman wrote: > Get word-level granularity from hardware for calculating > the transfer count remaining. > diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c > +static int tegra_dma_wcount_in_bytes(struct dma_chan *dc) A lot of the code in this function is identical to the code in tegra_dma_terminate_all() which does the same thing. Can this be pulled out into a shared utility function? > + tegra_dma_pause(tdc, true); Is this continual pausing/resuming of the DMA operation going to negatively affect performance? > + /* in case of interrupt, handle it and don't read wcount reg */ > + status = tdc_read(tdc, TEGRA_APBDMA_CHAN_STATUS); > + if (status & TEGRA_APBDMA_STATUS_ISE_EOC) { > + tdc_write(tdc, TEGRA_APBDMA_CHAN_STATUS, status); > + dev_info(tdc2dev(tdc), "%s():handling isr\n", __func__); If you swap the order of patches 1 and 2, then you can just add that line as dev_dbg() from the start, and you won't need to change it in the next patch. > + tdc->isr_handler(tdc, false); > + tegra_dma_resume(tdc); > + return 0; Why resume and return here? Shouldn't those last 2 lines be removed, so the code can simply continue through the balance of the function and return the actual status. tegra_dma_terminate_all() does that. > @@ -812,9 +851,22 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, > list_for_each_entry(sg_req, &tdc->pending_sg_req, node) { > dma_desc = sg_req->dma_desc; > if (dma_desc->txd.cookie == cookie) { > + hw_byte_count = tegra_dma_wcount_in_bytes(dc); > + > + if (!list_empty(&tdc->pending_sg_req)) Since this code is inside a loop that iterates over tha list, I don't think the list can ever be empty. > + first_entry = > + list_first_entry(&tdc->pending_sg_req, > + typeof(*first_entry), node); > + > residual = dma_desc->bytes_requested - > (dma_desc->bytes_transferred % > dma_desc->bytes_requested); > + > + /* hw byte count only applies to current transaction */ > + if (first_entry && > + first_entry->dma_desc->txd.cookie == cookie) > + residual -= hw_byte_count; > + > dma_set_residue(txstate, residual); Why not re-order the added code so that all the new code is added in one place, and the hw_byte_count value is only calculated if it's used, i.e.: residual = ...; first_entry = ...; if (sg_reg == first_entry) { hw_byte_count = ...; residual -= hw_byte_count; } -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html