Hi Andy, andriy.shevchenko@xxxxxxxxxxxxxxx wrote on Thu, 10 Mar 2022 19:50:09 +0200: > +Cc: Ilpo who is currently doing adjoining stuff. > > Ilpo, this one affects Intel Bay Trail and Cherry Trail platforms. > Not sure if it's in scope of your interest right now, but it might > be useful to see how DMA <--> 8250 UART functioning. > > On Thu, Mar 10, 2022 at 04:57:53PM +0100, Miquel Raynal wrote: > > As investigated by Phil Edworthy <phil.edworthy@xxxxxxxxxxx> on RZN1 a > > Email can be dropped as you put it below, just (full) name is enough. Sure. > I'm wondering if Phil or anybody else who possess the hardware can > test / tested this. I have a board with an RZN1 SoC but I don't have exactly the same setup as Phil (I only have one port with DMA working, while he used two as a loopback device). I tried to reproduce the error with no luck so far. I however verified that there was apparently no performance hit whatsoever due to this change. IIRC Phil does not have the hardware anymore. > > while ago, pausing a partial transfer only causes data to be written to > > memory that is a multiple of the memory width setting. Such a situation > > can happen eg. because of a char timeout interrupt on a UART. In this > > case, the current ->terminate_all() implementation does not always flush > > the remaining data as it should. > > > > In order to workaround this, a solutions is to resume and then pause > > again the transfer before termination. The resume call in practice > > actually flushes the remaining data. > > Perhaps Fixes tag? I don't know exactly what hardware can suffer from this, hence I decided not to add a Fixes tag given the fact that it was only observed on RZN1 (which was until now not yet supported upstream). > > Reported-by: Phil Edworthy <phil.edworthy@xxxxxxxxxxx> > > Suggested-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> > > Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx> > > --- > > drivers/dma/dw/core.c | 4 ++++ > > 1 file changed, 4 insertions(+) > > > > diff --git a/drivers/dma/dw/core.c b/drivers/dma/dw/core.c > > index 7ab83fe601ed..2f6183177ba5 100644 > > --- a/drivers/dma/dw/core.c > > +++ b/drivers/dma/dw/core.c > > @@ -862,6 +862,10 @@ static int dwc_terminate_all(struct dma_chan *chan) > > > > clear_bit(DW_DMA_IS_SOFT_LLP, &dwc->flags); > > > > + /* Ensure the last byte(s) are drained before disabling the channel */ > > + if (test_bit(DW_DMA_IS_PAUSED, &dwc->flags)) > > + dwc_chan_resume(dwc, true); > > + > > dwc_chan_pause(dwc, true); > > > > dwc_chan_disable(dw, dwc); > > -- > > 2.27.0 > > > Thanks, Miquèl
