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

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Message-ID: <b7fd3fac-77e4-7aad-e97a-c210aeb53773@quicinc.com>
Date: Wed, 7 Aug 2024 22:49:42 +0530
From: Mrinmay Sarkar <quic_msarkar@...cinc.com>
To: Serge Semin <fancer.lancer@...il.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 8/7/2024 4:26 AM, Serge Semin wrote:
> 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.
Ideally HDMA_V0_STOP_INT_MASK and HDMA_V0_ABORT_INT_MASK masks affect
both local and remote IRQs.

As per DW HDMA "Interrupts and Error Handling" figure 
HDMA_INT_SETUP_OFF_[WR|
RD] mask of the IRQ delivered via the edma_int[] wire.
And IMWr TLPs generation depend on 3 flags i.e HDMA_INT_SETUP_OFF_[WR|
RD].RSIE flag for stop IMWr, RWIE flag for watermark IMWr and 
HDMA_INT_SETUP_OFF_[WR|R
D].RAIE flag for abort IMWr generation.

Thanks,
Mrinmay
>>>> +		/* 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
>>>>