Messages in this thread | | | Date | Wed, 11 Oct 2023 13:51:28 +0300 | From | Serge Semin <> | Subject | Re: [PATCH v3 6/6] dmaengine: dw-edma: eDMA: Add sync read before starting the DMA transfer in remote setup |
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On Wed, Oct 11, 2023 at 10:11:45AM +0200, Kory Maincent wrote: > The Linked list element and pointer are not stored in the same memory as > the eDMA controller register. If the doorbell register is toggled before > the full write of the linked list a race condition error can appears.
s/can appears/will occur
> In remote setup we can only use a readl to the memory to assured the full
s/assured/assure
> write has occurred. > > Fixes: 7e4b8a4fbe2c ("dmaengine: Add Synopsys eDMA IP version 0 support") > Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
-Serge(y)
> --- > > Changes in v2: > - New patch > --- > drivers/dma/dw-edma/dw-edma-v0-core.c | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/drivers/dma/dw-edma/dw-edma-v0-core.c b/drivers/dma/dw-edma/dw-edma-v0-core.c > index b38786f0ad79..6245b720fbfe 100644 > --- a/drivers/dma/dw-edma/dw-edma-v0-core.c > +++ b/drivers/dma/dw-edma/dw-edma-v0-core.c > @@ -346,6 +346,20 @@ static void dw_edma_v0_core_write_chunk(struct dw_edma_chunk *chunk) > dw_edma_v0_write_ll_link(chunk, i, control, chunk->ll_region.paddr); > } > > +static void dw_edma_v0_sync_ll_data(struct dw_edma_chunk *chunk) > +{ > + /* > + * In case of remote eDMA engine setup, the DW PCIe RP/EP internals > + * configuration registers and Application memory are normally accessed > + * over different buses. Ensure LL-data reaches the memory before the > + * doorbell register is toggled by issuing the dummy-read from the remote > + * LL memory in a hope that the posted MRd TLP will return only after the > + * last MWr TLP is completed > + */ > + if (!(chunk->chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL)) > + readl(chunk->ll_region.vaddr.io); > +} > + > static void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first) > { > struct dw_edma_chan *chan = chunk->chan; > @@ -412,6 +426,9 @@ static void dw_edma_v0_core_start(struct dw_edma_chunk *chunk, bool first) > SET_CH_32(dw, chan->dir, chan->id, llp.msb, > upper_32_bits(chunk->ll_region.paddr)); > } > + > + dw_edma_v0_sync_ll_data(chunk); > + > /* Doorbell */ > SET_RW_32(dw, chan->dir, doorbell, > FIELD_PREP(EDMA_V0_DOORBELL_CH_MASK, chan->id)); > > -- > 2.25.1 >
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