On Thu, 2013-01-24 at 10:37 +0530, Viresh Kumar wrote: > On Wed, Jan 23, 2013 at 9:07 PM, Andy Shevchenko > <andriy.shevche...@linux.intel.com> wrote: > > diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c > > > static void dwc_scan_descriptors(struct dw_dma *dw, struct dw_dma_chan > > *dwc) > > { > > dma_addr_t llp; > > @@ -410,6 +441,8 @@ static void dwc_scan_descriptors(struct dw_dma *dw, > > struct dw_dma_chan *dwc) > > */ > > desc = dwc_first_active(dwc); > > > > + dwc_update_residue(dwc, desc); > > + > > if (dwc->tx_node_active != &desc->tx_list) { > > child = to_dw_desc(dwc->tx_node_active); > > Is there a point updating residue here? I don't have a very good knowledge of > nollp transfers but this is what i know... > > The above "if" will pass if we are still doing transfers and fail if > all transfers are done. > After the end of each LLI we receive an interrupt, where we queue next > LLI. Better > would be to initialize dwc->residue at dwc_dostart() with total > length, start decrementing > it with desc->len for every lli interrupt we get
It's mostly okay, but we have to handle few cases: - we have only first (master) descriptor - we have a chain of the descriptors: master + children - we have finished last transfer >From my point of view we can't fully get rid of dwc_update_residue(), but modify it a bit (drop away for loop). > and if call for > getting residue comes in > middle of transfer, simple return residue - dwc_get_sent(desc) without > updating residue > field... Where? In the tx_status to call something which returns dwc->residue - dwc_get_sent() ? > > > @@ -436,6 +469,9 @@ static void dwc_scan_descriptors(struct dw_dma *dw, > > struct dw_dma_chan *dwc) > > > > if (test_bit(DW_DMA_IS_SOFT_LLP, &dwc->flags)) { > > dev_vdbg(chan2dev(&dwc->chan), "%s: soft LLP mode\n", > > __func__); > > + > > + dwc_update_residue(dwc, dwc_first_active(dwc)); > > + > > same is applicable here too and so you can get rid of > dwc_update_residue() routine. Same thoughts as above are applicable to this. > > spin_unlock_irqrestore(&dwc->lock, flags); > > return; > > } > > @@ -444,6 +480,9 @@ static void dwc_scan_descriptors(struct dw_dma *dw, > > struct dw_dma_chan *dwc) > > (unsigned long long)llp); > > > > list_for_each_entry_safe(desc, _desc, &dwc->active_list, desc_node) > > { > > + /* initial residue value */ > > + dwc->residue = desc->total_len; > > + > > /* check first descriptors addr */ > > if (desc->txd.phys == llp) { > > spin_unlock_irqrestore(&dwc->lock, flags); > > @@ -453,16 +492,21 @@ static void dwc_scan_descriptors(struct dw_dma *dw, > > struct dw_dma_chan *dwc) > > /* check first descriptors llp */ > > if (desc->lli.llp == llp) { > > /* This one is currently in progress */ > > + dwc->residue -= dwc_get_sent(dwc); > > spin_unlock_irqrestore(&dwc->lock, flags); > > return; > > } > > > > - list_for_each_entry(child, &desc->tx_list, desc_node) > > + dwc->residue -= desc->len; > > + list_for_each_entry(child, &desc->tx_list, desc_node) { > > if (child->lli.llp == llp) { > > /* Currently in progress */ > > + dwc->residue -= dwc_get_sent(dwc); > > spin_unlock_irqrestore(&dwc->lock, flags); > > return; > > } > > + dwc->residue -= child->len; > > + } > > > > /* > > * No descriptors so far seem to be in progress, i.e. > > @@ -1058,6 +1102,7 @@ dwc_tx_status(struct dma_chan *chan, > > struct dma_tx_state *txstate) > > { > > struct dw_dma_chan *dwc = to_dw_dma_chan(chan); > > + unsigned long flags; > > enum dma_status ret; > > > > ret = dma_cookie_status(chan, cookie, txstate); > > @@ -1067,8 +1112,12 @@ dwc_tx_status(struct dma_chan *chan, > > ret = dma_cookie_status(chan, cookie, txstate); > > } > > > > + spin_lock_irqsave(&dwc->lock, flags); > > + > > why do you need locking here? What about the case when one CPU is getting an interrupt and runs scan_descriptors when the other, for example, in the middle of tx_status? So, I'm afraid the dma_set_residue(txstate, dwc->residue) is not atomic and we might end up with random numbers here. > > if (ret != DMA_SUCCESS) > > - dma_set_residue(txstate, dwc_first_active(dwc)->len); > > + dma_set_residue(txstate, dwc->residue); > > + > > + spin_unlock_irqrestore(&dwc->lock, flags); > > > > if (dwc->paused) > > return DMA_PAUSED; > > diff --git a/drivers/dma/dw_dmac_regs.h b/drivers/dma/dw_dmac_regs.h > > index 833b4cf..88dd8eb 100644 > > --- a/drivers/dma/dw_dmac_regs.h > > +++ b/drivers/dma/dw_dmac_regs.h > > @@ -203,6 +203,7 @@ struct dw_dma_chan { > > struct list_head active_list; > > struct list_head queue; > > struct list_head free_list; > > + u32 residue; > > struct dw_cyclic_desc *cdesc; > > > > unsigned int descs_allocated; -- Andy Shevchenko <andriy.shevche...@linux.intel.com> Intel Finland Oy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/