Re: [PATCH v3] dma: add driver for R-Car HPB-DMAC

[Sergei Shtylyov]

Hello.

On 09/14/2013 10:33 PM, Guennadi Liakhovetski wrote:

> > From: Max Filippov <max.filippov@xxxxxxxxxxxxxxxxxx>

> > Add support for HPB-DMAC found in Renesas R-Car SoCs, using 'shdma-base' DMA
> > driver framework.

> > Based on the original patch by Phil Edworthy <phil.edworthy@xxxxxxxxxxx>.

> > Signed-off-by: Max Filippov <max.filippov@xxxxxxxxxxxxxxxxxx>
> > [Sergei: removed useless #include, sorted #include's, fixed HPB_DMA_TCR_MAX,
> > fixed formats and removed line breaks in the dev_dbg() calls, rephrased and
> > added IRQ # to the shdma_request_irq() failure message, added MODULE_AUTHOR(),
> > removed '__init'/'__exit' annotations from the probe()/remove() methods, removed
> > '__initdata' annotation from 'hpb_dmae_driver', fixed guard macro name in the
> > header file, fixed #define ASYNCRSTR_ASRST20, added #define ASYNCRSTR_ASRST24,
> > added the necessary runtime PM calls to the probe() and remove() methods,
> > handled errors returned by dma_async_device_register(), beautified comments
> > and #define's.]
> > Signed-off-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>

> > ---

> [snip]

> > Index: slave-dma/drivers/dma/sh/rcar-hpbdma.c
> > ===================================================================
> > --- /dev/null
> > +++ slave-dma/drivers/dma/sh/rcar-hpbdma.c
> > @@ -0,0 +1,655 @@

> [snip]

> > +static int hpb_dmae_chan_probe(struct hpb_dmae_device *hpbdev, int id)
> > +{
> > +	struct shdma_dev *sdev = &hpbdev->shdma_dev;
> > +	struct platform_device *pdev =
> > +		to_platform_device(hpbdev->shdma_dev.dma_dev.dev);
> > +	struct hpb_dmae_chan *new_hpb_chan;
> > +	struct shdma_chan *schan;
> > +
> > +	/* Alloc channel */
> > +	new_hpb_chan = devm_kzalloc(&pdev->dev,
> > +				    sizeof(struct hpb_dmae_chan), GFP_KERNEL);
> > +	if (!new_hpb_chan) {
> > +		dev_err(hpbdev->shdma_dev.dma_dev.dev,
> > +			"No free memory for allocating DMA channels!\n");
> > +		return -ENOMEM;
> > +	}
> > +
> > +	schan = &new_hpb_chan->shdma_chan;

> A suggestion for an incremental patch - you might want to initialise the
> max_xfer_len field like

> 	schan->max_xfer_len = 64 * 1024 * 1024 - 1;

   IIRC, the HPB-DMAC's maximum transfer length is 16 MiB, without -1. You 
probably mixed it with LBSC-DMAC which is indeed capable of 64 MiB.

> because if it isn't initialised your max transfer length will be 4k,
> which will hurt your performance. I think you should get a better
> throughput after that

   OK, note taken. We'll look into it.

WBR, Sergei

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