20.06.2019 11:38, Jon Hunter пишет: > > On 18/06/2019 12:50, Dmitry Osipenko wrote: >> Tegra's APB DMA engine updates words counter after each transferred burst >> of data, hence it can report transfer's residual with more fidelity which >> may be required in cases like audio playback. In particular this fixes >> audio stuttering during playback in a chromiuim web browser. The patch is >> based on the original work that was made by Ben Dooks. It was tested on >> Tegra20 and Tegra30 devices. >> >> Link: >> https://lore.kernel.org/lkml/20190424162348.23692-1-ben.do...@codethink.co.uk/ >> Inspired-by: Ben Dooks <ben.do...@codethink.co.uk> >> Signed-off-by: Dmitry Osipenko <dig...@gmail.com> >> --- >> >> Changelog: >> >> v2: Addressed review comments made by Jon Hunter to v1. We won't try >> to get words count if dma_desc is on free list as it will result >> in a NULL dereference because this case wasn't handled properly. >> >> The residual value is now updated properly, avoiding potential >> integer overflow by adding the "bytes" to the "bytes_transferred" >> instead of the subtraction. >> >> drivers/dma/tegra20-apb-dma.c | 33 ++++++++++++++++++++++++++------- >> 1 file changed, 26 insertions(+), 7 deletions(-) >> >> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c >> index 79e9593815f1..fed18bc46479 100644 >> --- a/drivers/dma/tegra20-apb-dma.c >> +++ b/drivers/dma/tegra20-apb-dma.c >> @@ -797,6 +797,28 @@ static int tegra_dma_terminate_all(struct dma_chan *dc) >> return 0; >> } >> >> +static unsigned int tegra_dma_sg_bytes_xferred(struct tegra_dma_channel >> *tdc, >> + struct tegra_dma_sg_req *sg_req) >> +{ >> + unsigned long status, wcount = 0; >> + >> + if (!list_is_first(&sg_req->node, &tdc->pending_sg_req)) >> + return 0; >> + >> + if (tdc->tdma->chip_data->support_separate_wcount_reg) >> + wcount = tdc_read(tdc, TEGRA_APBDMA_CHAN_WORD_TRANSFER); >> + >> + status = tdc_read(tdc, TEGRA_APBDMA_CHAN_STATUS); >> + >> + if (!tdc->tdma->chip_data->support_separate_wcount_reg) >> + wcount = status; >> + >> + if (status & TEGRA_APBDMA_STATUS_ISE_EOC) >> + return sg_req->req_len; >> + >> + return get_current_xferred_count(tdc, sg_req, wcount); >> +} >> + >> static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, >> dma_cookie_t cookie, struct dma_tx_state *txstate) >> { >> @@ -806,6 +828,7 @@ static enum dma_status tegra_dma_tx_status(struct >> dma_chan *dc, >> enum dma_status ret; >> unsigned long flags; >> unsigned int residual; >> + unsigned int bytes = 0; >> >> ret = dma_cookie_status(dc, cookie, txstate); >> if (ret == DMA_COMPLETE) >> @@ -825,6 +848,7 @@ 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) { >> + bytes = tegra_dma_sg_bytes_xferred(tdc, sg_req); >> ret = dma_desc->dma_status; >> goto found; >> } >> @@ -836,7 +860,7 @@ static enum dma_status tegra_dma_tx_status(struct >> dma_chan *dc, >> found: >> if (dma_desc && txstate) { >> residual = dma_desc->bytes_requested - >> - (dma_desc->bytes_transferred % >> + ((dma_desc->bytes_transferred + bytes) % >> dma_desc->bytes_requested); >> dma_set_residue(txstate, residual); >> } >> @@ -1441,12 +1465,7 @@ static int tegra_dma_probe(struct platform_device >> *pdev) >> BIT(DMA_SLAVE_BUSWIDTH_4_BYTES) | >> BIT(DMA_SLAVE_BUSWIDTH_8_BYTES); >> tdma->dma_dev.directions = BIT(DMA_DEV_TO_MEM) | BIT(DMA_MEM_TO_DEV); >> - /* >> - * XXX The hardware appears to support >> - * DMA_RESIDUE_GRANULARITY_BURST-level reporting, but it's >> - * only used by this driver during tegra_dma_terminate_all() >> - */ >> - tdma->dma_dev.residue_granularity = DMA_RESIDUE_GRANULARITY_SEGMENT; >> + tdma->dma_dev.residue_granularity = DMA_RESIDUE_GRANULARITY_BURST; >> tdma->dma_dev.device_config = tegra_dma_slave_config; >> tdma->dma_dev.device_terminate_all = tegra_dma_terminate_all; >> tdma->dma_dev.device_tx_status = tegra_dma_tx_status; >> > > Looks good to me. Thanks for fixing! > > Reviewed-by: Jon Hunter <jonath...@nvidia.com>
Thanks to you too for the review :)
