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For HDMA, place watermarks at descriptor ends, > > > before link entries, and every four entries when a descriptor exceeds the > > > usable ring capacity or another issued descriptor follows. A later patch > > > handles these watermarks as progress events. > > > > > > Four entries is an empirically chosen coalescing interval. > > > > > > Signed-off-by: Koichiro Den > > > --- > > > Changes in v2: > > > - Fix the zero-based interval so the first watermark is on the fourth > > > entry, not the fifth. > > > - Revise the commit message and source comments. > > > > > > drivers/dma/dw-edma/dw-edma-core.c | 8 +++++++- > > > drivers/dma/dw-edma/dw-edma-core.h | 2 ++ > > > drivers/dma/dw-edma/dw-edma-v0-core.c | 10 ++++++++++ > > > drivers/dma/dw-edma/dw-hdma-v0-core.c | 28 +++++++++++++++++++++++++++ > > > 4 files changed, 47 insertions(+), 1 deletion(-) > > > > > > diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c > > > index a9f25a65294e..78d1bb6302fb 100644 > > > --- a/drivers/dma/dw-edma/dw-edma-core.c > > > +++ b/drivers/dma/dw-edma/dw-edma-core.c > > > @@ -98,6 +98,12 @@ static u32 dw_edma_core_get_free_num(struct dw_edma_chan *chan) > > > chan->ll_max; > > > } > > > > > > +static bool dw_edma_core_enable_ll_irq(struct dw_edma_desc *desc, u32 i, > > > + u32 free) > > > +{ > > > + return desc->chan->dw->core->ll_irq(desc, i, free); > > > +} > > > + > > > static void dw_edma_core_ll_start(struct dw_edma_desc *desc) > > > { > > > struct dw_edma_chan *chan = desc->chan; > > > @@ -120,7 +126,7 @@ static void dw_edma_core_ll_start(struct dw_edma_desc *desc) > > > > > > dw_edma_core_ll_data(chan, &desc->burst[i], > > > chan->ll_head, chan->cb, > > > - i == desc->nburst - 1 || free == 1); > > > + dw_edma_core_enable_ll_irq(desc, i, free)); > > > > > > chan->ll_head++; > > > > > > diff --git a/drivers/dma/dw-edma/dw-edma-core.h b/drivers/dma/dw-edma/dw-edma-core.h > > > index f2c2d5af1fff..8ed37e8a12cb 100644 > > > --- a/drivers/dma/dw-edma/dw-edma-core.h > > > +++ b/drivers/dma/dw-edma/dw-edma-core.h > > > @@ -162,6 +162,8 @@ struct dw_edma_core_ops { > > > void (*ll_link)(struct dw_edma_chan *chan, u32 idx, bool cb, u64 addr); > > > void (*ll_clear)(struct dw_edma_chan *chan, u32 idx); > > > int (*ll_cur_idx)(struct dw_edma_chan *chan); > > > + /* Called with chan->vc.lock held. */ > > > + bool (*ll_irq)(struct dw_edma_desc *desc, u32 i, u32 free); > > > void (*ch_doorbell)(struct dw_edma_chan *chan); > > > void (*ch_enable)(struct dw_edma_chan *chan); > > > void (*ch_config)(struct dw_edma_chan *chan); > > > diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c > > > index c31fff095b4f..62141aa32e50 100644 > > > --- a/drivers/dma/dw-edma/dw-edma-v0-core.c > > > +++ b/drivers/dma/dw-edma/dw-edma-v0-core.c > > > @@ -649,6 +649,15 @@ static int dw_edma_v0_core_ll_cur_idx(struct dw_edma_chan *chan) > > > return (val - base) / EDMA_LL_SZ; > > > } > > > > > > +static bool dw_edma_v0_core_ll_irq(struct dw_edma_desc *desc, u32 i, u32 free) > > > +{ > > > + /* > > > + * eDMA reports LL interrupts through DONE. Keep them at > > > + * descriptor ends, plus the last free slot to refill the ring. > > > + */ > > > + return i == desc->nburst - 1 || free == 1; > > > +} > > > + > > > /* eDMA debugfs callbacks */ > > > static void dw_edma_v0_core_debugfs_on(struct dw_edma *dw) > > > { > > > @@ -685,6 +694,7 @@ static const struct dw_edma_core_ops dw_edma_v0_core = { > > > .ll_link = dw_edma_v0_core_ll_link, > > > .ll_clear = dw_edma_v0_core_ll_clear, > > > .ll_cur_idx = dw_edma_v0_core_ll_cur_idx, > > > + .ll_irq = dw_edma_v0_core_ll_irq, > > > .ch_doorbell = dw_edma_v0_core_ch_doorbell, > > > .ch_enable = dw_edma_v0_core_ch_enable, > > > .ch_config = dw_edma_v0_core_ch_config, > > > diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c > > > index b2d35f0b7b6d..fb651a83f0f3 100644 > > > --- a/drivers/dma/dw-edma/dw-hdma-v0-core.c > > > +++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c > > > @@ -13,6 +13,9 @@ > > > #include "dw-hdma-v0-regs.h" > > > #include "dw-hdma-v0-debugfs.h" > > > > > > +/* Empirically chosen watermark interval. */ > > > +#define HDMA_V0_WATERMARK_INTERVAL 4 > > > + > > > enum dw_hdma_control { > > > DW_HDMA_V0_CB = BIT(0), > > > DW_HDMA_V0_TCB = BIT(1), > > > @@ -417,6 +420,30 @@ static int dw_hdma_v0_core_ll_cur_idx(struct dw_edma_chan *chan) > > > return (val - base) / EDMA_LL_SZ; > > > } > > > > > > +static bool dw_hdma_v0_core_ll_irq(struct dw_edma_desc *desc, u32 i, u32 free) > > > +{ > > > + struct dw_edma_chan *chan = desc->chan; > > > + bool needs_progress; > > > + > > > + /* > > > + * Always place a watermark at a descriptor end and before the link > > > + * element. The first reports descriptor progress; the second provides > > > + * one progress point per ring lap. > > > + */ > > > + if (i == desc->nburst - 1 || chan->ll_head == chan->ll_max - 1) > > > + return true; > > > + > > > + /* > > > + * Use periodic watermarks when a descriptor exceeds the usable ring or > > > + * when more issued work follows it. > > > + */ > > > + needs_progress = desc->nburst > chan->ll_max - 1 || > > > + !list_is_last(&desc->vd.node, &chan->vc.desc_issued); > > > + > > > + return needs_progress && > > > + (chan->ll_head + 1) % HDMA_V0_WATERMARK_INTERVAL == 0; > > > > This is not good layer design. edma/hdma supposed just do action to operate > > register, less software logic. > > Indeed, thanks for pointing that out. > > > > > Can we move this code to core layer? introduce an 'interval' for difference > > backend. > > > > eDMA: interval is number description. > > hDMA: interval is HDMA_V0_WATERMARK_INTERVAL > > Sorry, by "eDMA: interval is number description", do you mean using desc->nburst > as the "interval", so eDMA keeps one interrupt at the end of each descriptor? Yes, of cource, you also can periodic interval check eDMA if want. Frank > > > > > So core layer can use unified logic to handle for both eDMA and hDMA? > > I'll move as much of the software policy as possible into the common core. I > think even the periodic interval and descriptor-end placement can be shared. > I'll rework this part and verify it with performance tests. > > Thanks for the review and suggestion. Much appreciated. > Koichiro > > > > > Frank > > > > > +} > > > + > > > /* HDMA debugfs callbacks */ > > > static void dw_hdma_v0_core_debugfs_on(struct dw_edma *dw) > > > { > > > @@ -441,6 +468,7 @@ static const struct dw_edma_core_ops dw_hdma_v0_core = { > > > .ll_link = dw_hdma_v0_core_ll_link, > > > .ll_clear = dw_hdma_v0_core_ll_clear, > > > .ll_cur_idx = dw_hdma_v0_core_ll_cur_idx, > > > + .ll_irq = dw_hdma_v0_core_ll_irq, > > > .ch_doorbell = dw_hdma_v0_core_ch_doorbell, > > > .ch_enable = dw_hdma_v0_core_ch_enable, > > > .ch_config = dw_hdma_v0_core_ch_config, > > > -- > > > 2.51.0 > > >