linux-kernel - Re: [PATCH v1] dmaengine: tegra-apb: Error out if DMA_PREP

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Date:   Thu, 30 May 2019 20:32:17 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Vinod Koul <vkoul@...nel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Ben Dooks <ben.dooks@...ethink.co.uk>
Cc:     dmaengine@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] dmaengine: tegra-apb: Error out if DMA_PREP_INTERRUPT
 flag is unset

30.05.2019 15:01, Jon Hunter пишет:
> 
> On 29/05/2019 22:43, Dmitry Osipenko wrote:
>> Apparently driver was never tested with DMA_PREP_INTERRUPT flag being
>> unset since it completely disables interrupt handling instead of skipping
>> the callbacks invocations, hence putting channel into unusable state.
>>
>> The flag is always set by all of kernel drivers that use APB DMA, so let's
>> error out in otherwise case for consistency. It won't be difficult to
>> support that case properly if ever will be needed.
>>
>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>> ---
>>  drivers/dma/tegra20-apb-dma.c | 12 ++++++++++--
>>  1 file changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
>> index cf462b1abc0b..2c84a660ba36 100644
>> --- a/drivers/dma/tegra20-apb-dma.c
>> +++ b/drivers/dma/tegra20-apb-dma.c
>> @@ -988,8 +988,12 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_slave_sg(
>>  		csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
>>  	}
>>  
>> -	if (flags & DMA_PREP_INTERRUPT)
>> +	if (flags & DMA_PREP_INTERRUPT) {
>>  		csr |= TEGRA_APBDMA_CSR_IE_EOC;
>> +	} else {
>> +		WARN_ON_ONCE(1);
>> +		return NULL;
>> +	}
>>  
>>  	apb_seq |= TEGRA_APBDMA_APBSEQ_WRAP_WORD_1;
>>  
>> @@ -1131,8 +1135,12 @@ static struct dma_async_tx_descriptor *tegra_dma_prep_dma_cyclic(
>>  		csr |= tdc->slave_id << TEGRA_APBDMA_CSR_REQ_SEL_SHIFT;
>>  	}
>>  
>> -	if (flags & DMA_PREP_INTERRUPT)
>> +	if (flags & DMA_PREP_INTERRUPT) {
>>  		csr |= TEGRA_APBDMA_CSR_IE_EOC;
>> +	} else {
>> +		WARN_ON_ONCE(1);
>> +		return NULL;
>> +	}
>>  
>>  	apb_seq |= TEGRA_APBDMA_APBSEQ_WRAP_WORD_1;
> 
> Looks good to me.
> 
> Acked-by: Jon Hunter <jonathanh@...dia.com>
> 
> Cheers
> Jon
> 

Thanks