Re: [PATCH v2 1/8] spi: imx: Fix DMA transfer

[Anton Bondarenko]

On 08.10.2015 11:19, Robin Gong wrote:
> On Thu, Oct 01, 2015 at 12:02:41AM +0000, Bondarenko, Anton wrote:
> > > > @@ -201,9 +202,8 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
> > > >   {
> > > >   	struct spi_imx_data *spi_imx = spi_master_get_devdata(master);
> > > >
> > > > -	if (spi_imx->dma_is_inited
> > > > -	    && transfer->len > spi_imx->rx_wml * sizeof(u32)
> > > > -	    && transfer->len > spi_imx->tx_wml * sizeof(u32))
> > > > +	if (spi_imx->dma_is_inited &&
> > > > +	    (transfer->len > spi_imx->wml * sizeof(u32)))
> > > Add Sascha in the loop. I don't think "* sizeof(u32)", since even 1 byte data
> > > will consume one position of 32bit FIFO Thus if here
> > > spi_imx->wml = spi_imx_get_fifosize(spi_imx) / 2 = 32, the threshold value
> > > which judge DMA mode used or not should be 32 not 32 * 4.
> > > Of course, it will not cause any function break since both DMA and PIO can work
> > > ,but I think we'd better correct it.
> > I agree, in case of 1 byte SPI word we do not need to multiply by 4.
> > But for 16 bit and 32 bit SPI words it's necessary. This part is
> > addressed in patch 3.
> > I could remove "* sizeof(u32)" for now.
> I still think don't need *sizeof(u32) even for 16bit and 32bit, whatever bits
> used as one spi word(<32bits), one spi word consume one position of SPI FIFO
> (32bit).
Will be removed in V3 for this patch.
> > > >   		return true;
> > > >   	return false;
> > > >   }

Regards,
Anton
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