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SubjectRe: [PATCH 09/15] dmaengine: img-mdc: Handle early status read
On 22-07-18, 23:20, Andreas Färber wrote:
> From: Damien Horsley <damien.horsley@imgtec.com>
>
> It is possible that mdc_tx_status may be called before the first
> node has been read from memory.
>
> In this case, the residue value stored in the register is undefined.
> Return the transfer size instead.
>
> Signed-off-by: Damien Horsley <damien.horsley@imgtec.com>
> Signed-off-by: Andreas Färber <afaerber@suse.de>
> ---
> drivers/dma/img-mdc-dma.c | 40 ++++++++++++++++++++++++----------------
> 1 file changed, 24 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/dma/img-mdc-dma.c b/drivers/dma/img-mdc-dma.c
> index 25cec9c243e1..0f2f0f52d83a 100644
> --- a/drivers/dma/img-mdc-dma.c
> +++ b/drivers/dma/img-mdc-dma.c
> @@ -621,25 +621,33 @@ static enum dma_status mdc_tx_status(struct dma_chan *chan,
> (MDC_CMDS_PROCESSED_CMDS_DONE_MASK + 1);
>
> /*
> - * If the command loaded event hasn't been processed yet, then
> - * the difference above includes an extra command.
> + * If the first node has not yet been read from memory,
> + * the residue register value is undefined

so is this the case when transfer is not started ?

> */
> - if (!mdesc->cmd_loaded)
> - cmds--;
> - else
> - cmds += mdesc->list_cmds_done;
> -
> - bytes = mdesc->list_xfer_size;
> - ldesc = mdesc->list;
> - for (i = 0; i < cmds; i++) {
> - bytes -= ldesc->xfer_size + 1;
> - ldesc = ldesc->next_desc;
> - }
> - if (ldesc) {
> - if (residue != MDC_TRANSFER_SIZE_MASK)
> - bytes -= ldesc->xfer_size - residue;
> + if (!mdesc->cmd_loaded && !cmds) {
> + bytes = mdesc->list_xfer_size;
> + } else {
> + /*
> + * If the command loaded event hasn't been processed yet, then
> + * the difference above includes an extra command.
> + */
> + if (!mdesc->cmd_loaded)
> + cmds--;
> else
> + cmds += mdesc->list_cmds_done;
> +
> + bytes = mdesc->list_xfer_size;
> + ldesc = mdesc->list;
> + for (i = 0; i < cmds; i++) {
> bytes -= ldesc->xfer_size + 1;
> + ldesc = ldesc->next_desc;
> + }
> + if (ldesc) {
> + if (residue != MDC_TRANSFER_SIZE_MASK)
> + bytes -= ldesc->xfer_size - residue;
> + else
> + bytes -= ldesc->xfer_size + 1;
> + }
> }
> }
> spin_unlock_irqrestore(&mchan->vc.lock, flags);
> --
> 2.16.4

--
~Vinod

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