| Message ID | 1441905466-17459-2-git-send-email-robert.jarzmik@free.fr (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Sep 10, 2015 at 07:17:46PM +0200, Robert Jarzmik wrote: > A very tiny temporal window exists in the residue calculation where : > - upon entering residue calculation, the transfer is ongoing > - when reading the current transfer pointer, it just changed to > the "finisher/linker" descriptor > > In this case, the he residue returned is thw whole transfer length > instead of 0. Fix it. Two many typos here :(
Vinod Koul <vinod.koul@intel.com> writes: > On Thu, Sep 10, 2015 at 07:17:46PM +0200, Robert Jarzmik wrote: >> A very tiny temporal window exists in the residue calculation where : >> - upon entering residue calculation, the transfer is ongoing >> - when reading the current transfer pointer, it just changed to >> the "finisher/linker" descriptor >> >> In this case, the he residue returned is thw whole transfer length >> instead of 0. Fix it. > Two many typos here :( Ah sorry for that, I'll resend a v2 today. Cheers.
diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c index 5647c1579c44..bf064277518e 100644 --- a/drivers/dma/pxa_dma.c +++ b/drivers/dma/pxa_dma.c @@ -1186,6 +1186,16 @@ static unsigned int pxad_residue(struct pxad_chan *chan, else curr = phy_readl_relaxed(chan->phy, DTADR); + /* + * curr has to be actually read before checking descriptor + * completion, so that a curr inside a status updater + * descriptor implies the following test returns true, and + * preventing reordering of curr load and the test. + */ + rmb(); + if (is_desc_completed(vd)) + goto out; + for (i = 0; i < sw_desc->nb_desc - 1; i++) { hw_desc = sw_desc->hw_desc[i]; if (sw_desc->hw_desc[0]->dcmd & PXA_DCMD_INCSRCADDR)
A very tiny temporal window exists in the residue calculation where : - upon entering residue calculation, the transfer is ongoing - when reading the current transfer pointer, it just changed to the "finisher/linker" descriptor In this case, the he residue returned is thw whole transfer length instead of 0. Fix it. This appears almost in one extreme case, where the driver is used by older clients which inquire for residue in interrupt context, such as the xmsc91x ethernet driver, in a tight loop : interrupt_handler() dmaengine_submit() do { dmaengine_tx_status() } while (residue > 0 || status != DMA_ERROR) Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> --- drivers/dma/pxa_dma.c | 10 ++++++++++ 1 file changed, 10 insertions(+)