linux-kernel - Re: [PATCH v2 1/2] dmaengine: dw-edma: Fix unmasking STOP and ABORT interrupts for HDMA

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Message-ID: <by7uqtmnx4jjxigbm3lrpp2b3eqcrq3byqrrmexmkkigtjxdir@o7ahdlhpgzjl>
Date: Wed, 7 Aug 2024 01:56:26 +0300
From: Serge Semin <fancer.lancer@...il.com>
To: Mrinmay Sarkar <quic_msarkar@...cinc.com>
Cc: manivannan.sadhasivam@...aro.org, vkoul@...nel.org, 
	quic_shazhuss@...cinc.com, quic_nitegupt@...cinc.com, quic_ramkri@...cinc.com, 
	quic_nayiluri@...cinc.com, quic_krichai@...cinc.com, quic_vbadigan@...cinc.com, 
	stable@...r.kernel.org, Cai Huoqing <cai.huoqing@...ux.dev>, dmaengine@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dmaengine: dw-edma: Fix unmasking STOP and ABORT
 interrupts for HDMA

On Mon, Aug 05, 2024 at 07:30:14PM +0530, Mrinmay Sarkar wrote:
> 
> On 8/2/2024 5:12 AM, Serge Semin wrote:
> > On Tue, Jul 23, 2024 at 06:49:31PM +0530, Mrinmay Sarkar wrote:
> > > The current logic is enabling both STOP_INT_MASK and ABORT_INT_MASK
> > > bit. This is apparently masking those particular interrupts rather than
> > > unmasking the same. If the interrupts are masked, they would never get
> > > triggered.
> > > 
> > > So fix the issue by unmasking the STOP and ABORT interrupts properly.
> > > 
> > > Fixes: e74c39573d35 ("dmaengine: dw-edma: Add support for native HDMA")
> > > cc: stable@...r.kernel.org
> > > Signed-off-by: Mrinmay Sarkar <quic_msarkar@...cinc.com>
> > > ---
> > >   drivers/dma/dw-edma/dw-hdma-v0-core.c | 9 +++++----
> > >   1 file changed, 5 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/dma/dw-edma/dw-hdma-v0-core.c b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> > > index 10e8f07..fa89b3a 100644
> > > --- a/drivers/dma/dw-edma/dw-hdma-v0-core.c
> > > +++ b/drivers/dma/dw-edma/dw-hdma-v0-core.c
> > > @@ -247,10 +247,11 @@ static void dw_hdma_v0_core_start(struct dw_edma_chunk *chunk, bool first)
> > >   	if (first) {
> > >   		/* Enable engine */
> > >   		SET_CH_32(dw, chan->dir, chan->id, ch_en, BIT(0));
> > > -		/* Interrupt enable&unmask - done, abort */
> > > -		tmp = GET_CH_32(dw, chan->dir, chan->id, int_setup) |
> > > -		      HDMA_V0_STOP_INT_MASK | HDMA_V0_ABORT_INT_MASK |
> > > -		      HDMA_V0_LOCAL_STOP_INT_EN | HDMA_V0_LOCAL_ABORT_INT_EN;
> > Just curious, if all the interrupts were actually masked, how has this
> > been even working?.. In other words if it affected both local and
> > remote interrupts, then the HDMA driver has never actually worked,
> > right?
> 

> Agreed, it should not work as interrupts were masked.
> 
> But as we are enabling LIE/RIE bits (LWIE/RWIE) that eventually enabling
> watermark
> interrupt in HDMA case and somehow on device I could see interrupt was
> generating with watermark and stop bit set and it was working.
> Since we were not clearing watermark interrupt, it was also causing storm of
> interrupt.

Is it possible that the HDMA_V0_STOP_INT_MASK and
HDMA_V0_ABORT_INT_MASK masks affect the local IRQs only? If so than
that shall explain why for instance Kory hasn't met the problem. 

Based on the "Interrupts and Error Handling" figures of the DW EDMA
databook the DMA_READ_INT_MASK_OFF/DMA_WRITE_INT_MASK_OFF CSRs mask of
the IRQ delivered via the edma_int[] wire. Meanwhile the IMWr TLPs
generation depend on the RIE/LLRAIE flags state only.

> 
> > > +		/* Interrupt unmask - STOP, ABORT */
> > > +		tmp = GET_CH_32(dw, chan->dir, chan->id, int_setup) &
> > > +		      ~HDMA_V0_STOP_INT_MASK & ~HDMA_V0_ABORT_INT_MASK;
> > Please convert this to:
> > +		/* Interrupt unmask - stop, abort */
> > +		tmp = GET_CH_32(dw, chan->dir, chan->id, int_setup);
> > +		tmp &= ~(HDMA_V0_STOP_INT_MASK | HDMA_V0_ABORT_INT_MASK);
> > 
> > -Serge(y)
> 
> Sure. Will do

Thanks.

-Serge(y)

> 
> Thanks,
> Mrinmay
> 
> > > +		/* Interrupt enable - STOP, ABORT */
> > > +		tmp |= HDMA_V0_LOCAL_STOP_INT_EN | HDMA_V0_LOCAL_ABORT_INT_EN;
> > >   		if (!(dw->chip->flags & DW_EDMA_CHIP_LOCAL))
> > >   			tmp |= HDMA_V0_REMOTE_STOP_INT_EN | HDMA_V0_REMOTE_ABORT_INT_EN;
> > >   		SET_CH_32(dw, chan->dir, chan->id, int_setup, tmp);
> > > -- 
> > > 2.7.4
> > >