Re: [PATCH 7/8] dmaengine: tegra20-apb-dma: Only calculate residue if txstate exists.
From: Jon Hunter <jonathanh@nvidia.com>
Date: 2016-06-08 09:00:55
Also in:
linux-arm-kernel, linux-tegra, lkml
Subsystem:
dma generic offload engine subsystem, tegra dma drivers, the rest · Maintainers:
Vinod Koul, Laxman Dewangan, Jon Hunter, Linus Torvalds
Hi Peter, On 07/06/16 18:38, Peter Griffin wrote:
quoted hunk ↗ jump to hunk
There is no point calculating the residue if there is no txstate to store the value. Signed-off-by: Peter Griffin <peter.griffin@linaro.org> --- drivers/dma/tegra20-apb-dma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c index 01e316f..7f4af8c 100644 --- a/drivers/dma/tegra20-apb-dma.c +++ b/drivers/dma/tegra20-apb-dma.c@@ -814,7 +814,7 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, unsigned int residual; ret = dma_cookie_status(dc, cookie, txstate); - if (ret == DMA_COMPLETE) + if (ret == DMA_COMPLETE || !txstate) return ret;
Thanks for reporting this. I agree that we should not do this, however, looking at the code for Tegra, I am wondering if this could change the actual state that is returned. Looking at dma_cookie_status() it will call dma_async_is_complete() which will return either DMA_COMPLETE or DMA_IN_PROGRESS. It could be possible that the actual state for the DMA transfer in the tegra driver is DMA_ERROR, so I am wondering if we should do something like the following ...
diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index 01e316f73559..45edab7418d0 100644
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c@@ -822,13 +822,8 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, /* Check on wait_ack desc status */ list_for_each_entry(dma_desc, &tdc->free_dma_desc, node) { if (dma_desc->txd.cookie == cookie) { - residual = dma_desc->bytes_requested - - (dma_desc->bytes_transferred % - dma_desc->bytes_requested); - dma_set_residue(txstate, residual); ret = dma_desc->dma_status; - spin_unlock_irqrestore(&tdc->lock, flags); - return ret; + goto found; } }
@@ -836,17 +831,23 @@ 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) { - residual = dma_desc->bytes_requested - - (dma_desc->bytes_transferred % - dma_desc->bytes_requested); - dma_set_residue(txstate, residual); ret = dma_desc->dma_status; - spin_unlock_irqrestore(&tdc->lock, flags); - return ret; + goto found; } } - dev_dbg(tdc2dev(tdc), "cookie %d does not found\n", cookie); + dev_warn(tdc2dev(tdc), "cookie %d not found\n", cookie); + spin_unlock_irqrestore(&tdc->lock, flags); + return ret; + +found: + if (txstate) { + residual = dma_desc->bytes_requested - + (dma_desc->bytes_transferred % + dma_desc->bytes_requested); + dma_set_residue(txstate, residual); + } + spin_unlock_irqrestore(&tdc->lock, flags); return ret; }
Cheers Jon -- nvpublic