[PATCH V4 04/14] DMA: PL330: Add DMA_CYCLIC capability

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Mon, Jul 25, 2011 at 07:31:45PM +0900, Boojin Kim wrote:
> > On Mon, Jul 25, 2011 at 10:28:22AM +0900, Boojin Kim wrote:
> > > +static void pl330_tasklet_cyclic(unsigned long data)
> > > +{
> > > +	struct dma_pl330_chan *pch = (struct dma_pl330_chan *)data;
> > > +	struct dma_pl330_desc *desc, *_dt;
> > > +	unsigned long flags;
> > > +	LIST_HEAD(list);
> > > +
> > > +	spin_lock_irqsave(&pch->lock, flags);
> > ...
> > > +			callback = desc->txd.callback;
> > > +			if (callback)
> > > +				callback(desc->txd.callback_param);
> >
> > On this again - what if the callback wants to terminate the DMA activity
> > because there's no more audio data to be sent/received from the device?
> 
> Do you mean what is happened if the callback() is called after channel is
> terminated ?
> Or What is happened if Callback() calls 'dma_release_channel()' to terminate
> DMA?

No.  I mean what if the callback wants to call dmaengine_terminate_all().

> > > +	if (!pch->cyclic_task) {
> > > +		pch->cyclic_task =
> > > +			kmalloc(sizeof(struct tasklet_struct), GFP_KERNEL);
> > > +		tasklet_init(pch->cyclic_task,
> > > +			pl330_tasklet_cyclic, (unsigned int)pch);
> >
> > Here you allocate memory for the cyclic task.  Above you set this pointer
> > to NULL.  That sounds like a memory leak to me.  Why are you kmallocing
> > this memory - why can't it be part of the dma_pl330_chan structure?  It's
> > only 28 bytes.
> 
> It's my mistake. I should have been free of the memory.
> 
> And the reason why I use kmalloc for 'cyclic_task' is following.
> This memory size for 'cyclic_tasklet' is the 896 bytes ( = the number of
> channel * sizeof(struct tasklet_struct)= 32*28) for each DMAC. And This
> memory size is increased according to the number of DMAC.
> And Samsung has the DMAC that is dedicated for Mem-to-Mem operation. If I
> make 'cyclic_task' be part of dma_pl330_chan, this DMAC that is dedicated
> for Mem-to-Mem operation should hold unused data.
> So, I think it's loss that all dma channels hold own 'cyclic_task'.

Could you re-use the tasklet that already exists?