On Tue, Nov 14, 2023 at 03:51:58PM +0100, Kory Maincent wrote:
> The Linked list element and pointer are not stored in the same memory as
> the HDMA controller register. If the doorbell register is toggled before
> the full write of the linked list a race condition error will occur.
> In remote setup we can only use a readl to the memory to assure the full
> write has occurred.
>
> Fixes: e74c39573d35 ("dmaengine: dw-edma: Add support for native HDMA")
> Reviewed-by: Serge Semin <fancer.lancer@xxxxxxxxx>
> Signed-off-by: Kory Maincent <kory.maincent@xxxxxxxxxxx>
Few nitpicks below. With those addressed,
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
> ---
>
> Changes in v2:
> - Move the sync read in a function.
> - Add commments
>
> Changes in v4:
> - Update git commit message.
> ---
> drivers/dma/dw-edma/dw-hdma-v0-core.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> index 04b0bcb6ded9..13b6aec6a6de 100644
> --- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
> +++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> @@ -222,6 +222,20 @@ static void dw_hdma_v0_core_write_chunk(struct dw_edma_chunk *chunk)
> dw_hdma_v0_write_ll_link(chunk, i, control, chunk->ll_region.paddr);
> }
>
> +static void dw_hdma_v0_sync_ll_data(struct dw_edma_chunk *chunk)
> +{
> + /*
> + * In case of remote HDMA engine setup, the DW PCIe RP/EP internals
s/internals/internal
> + * configuration registers and Application memory are normally accessed
s/Application/application
> + * 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
MRd TLP is not posted.
- Mani
> + * last MWr TLP is completed
> + */
> + if (!(chunk->chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL))
> + readl(chunk->ll_region.vaddr.io);
> +}
> +
> static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
> {
> struct dw_edma_chan *chan = chunk->chan;
> @@ -252,6 +266,9 @@ static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
> /* Set consumer cycle */
> SET_CH_32(dw, chan->dir, chan->id, cycle_sync,
> HDMA_V0_CONSUMER_CYCLE_STAT | HDMA_V0_CONSUMER_CYCLE_BIT);
> +
> + dw_hdma_v0_sync_ll_data(chunk);
> +
> /* Doorbell */
> SET_CH_32(dw, chan->dir, chan->id, doorbell, HDMA_V0_DOORBELL_START);
> }
>
> --
> 2.25.1
>
--
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