Re: [PATCH V3 2/6] dmaengine: change the flags of request_irq()

[Huang Shijie <b32955@freescale.com>]

Hi:

> Shawn Guo writes:
>> On Wed, Mar 30, 2011 at 11:03:02AM +0200, Lothar Waßmann wrote:
>>> Hi,
>>>
>>> Huang Shijie writes:
>>>> The GPMI may have many DMA channels, such as the imx23 has
>>>> four DMA channels. All these DMA channels share the same interrupt.
>>>> So change the flags from '0' to IRQF_SHARED, else there will be
>>>> an EBUSY error returns.
>>>>
>>>> Signed-off-by: Huang Shijie<b32955@freescale.com>
>>>> ---
>>>>   drivers/dma/mxs-dma.c |    2 +-
>>>>   1 files changed, 1 insertions(+), 1 deletions(-)
>>>>
>>>> diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
>>>> index 88aad4f..0ee5b52 100644
>>>> --- a/drivers/dma/mxs-dma.c
>>>> +++ b/drivers/dma/mxs-dma.c
>>>> @@ -328,7 +328,7 @@ static int mxs_dma_alloc_chan_resources(struct dma_chan *chan)
>>>>   	memset(mxs_chan->ccw, 0, PAGE_SIZE);
>>>>
>>>>   	ret = request_irq(mxs_chan->chan_irq, mxs_dma_int_handler,
>>>> -				0, "mxs-dma", mxs_dma);
>>>> +				IRQF_SHARED, "mxs-dma", mxs_dma);
>>>>   	if (ret)
>>>>   		goto err_irq;
>>>>
>>> IMO this is wrong. The interrupt is requested with all the same
>>> parameters for each DMA channel. So, actually it is not a shared IRQ,
>> The parameter mxs_chan->chan_irq is different for each channel, except
>> gpmi which has 4 channels sharing one irq.
>>
> That's what I mean. The other interrupts won't need the IRQF_SHARED
> flag anyway.
>
Ok. I will add a GPMI-INTERRUPT check in the mxs_dma_alloc_chan_resources().
>>> but an IRQ with the same handler registered multiple times, which is
>>> just nonsense.
>>>
>>> Instead of declaring it as shared, it would be more sensible to only
>>> register it for the first channel. Otherwise the handler will be
>>> called multiple times in case of an interrupt with only the first
>>> invocation doing all the work and the subsequent invocations just
>>> returning without doing anything.
>>>
>> -- 
>> Regards,
>> Shawn
>>
> Lothar Waßmann
Huang Shijie