Hi Shimoda-san
On Fri, 27 Jan 2012, Shimoda, Yoshihiro wrote:
> Hello Guennadi-san,
>
> 2012/01/26 23:56, Guennadi Liakhovetski wrote:
> > This patch adds a library of functions, helping to implement dmaengine
> > drivers for hardware, unable to handle scatter-gather lists natively.
> > The first version of this driver only supports memcpy and slave DMA
> > operation.
> >
> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> > ---
> >
> > v2:
> >
> > 1. switch from using a tasklet to threaded IRQ, which allowed to
>
> I tested this driver on 2 environment, but it could not work correctly.
> - renesas_usbhs driver with shdma driver on the mackerel board
> - renesas_usbhs driver with experimental SUDMAC driver
>
> In this case, should we modify the renesas_usbhs driver?
Yes, you do. Please, see the respective version of the shdma patch. It
doesn't request channel IRQs any more directly, instead, it uses a
dma-simple wrapper function. Also operations change a bit.
Thanks
Guennadi
> For reference, if I changed the threaded IRQ to tasklet,
> the 2 environment worked correctly:
> ==============
> diff --git a/drivers/dma/dma-simple.c b/drivers/dma/dma-simple.c
> index 49d8f7d..65a5170 100644
> --- a/drivers/dma/dma-simple.c
> +++ b/drivers/dma/dma-simple.c
> @@ -715,16 +715,18 @@ static irqreturn_t chan_irq(int irq, void *dev)
>
> spin_lock(&schan->chan_lock);
>
> - ret = ops->chan_irq(schan, irq) ? IRQ_WAKE_THREAD : IRQ_NONE;
> + ret = ops->chan_irq(schan, irq) ? IRQ_HANDLED : IRQ_NONE;
> + if (ret == IRQ_HANDLED)
> + tasklet_schedule(&schan->tasklet);
>
> spin_unlock(&schan->chan_lock);
>
> return ret;
> }
>
> -static irqreturn_t chan_irqt(int irq, void *dev)
> +static void chan_irqt(unsigned long dev)
> {
> - struct dma_simple_chan *schan = dev;
> + struct dma_simple_chan *schan = (struct dma_simple_chan *)dev;
> const struct dma_simple_ops *ops =
> to_simple_dev(schan->dma_chan.device)->ops;
> struct dma_simple_desc *sdesc;
> @@ -744,15 +746,13 @@ static irqreturn_t chan_irqt(int irq, void *dev)
> spin_unlock_irq(&schan->chan_lock);
>
> simple_chan_ld_cleanup(schan, false);
> -
> - return IRQ_HANDLED;
> }
>
> int dma_simple_request_irq(struct dma_simple_chan *schan, int irq,
> unsigned long flags, const char *name)
> {
> - int ret = request_threaded_irq(irq, chan_irq, chan_irqt,
> - flags, name, schan);
> + int ret = request_irq(irq, chan_irq, flags, name, schan);
> + tasklet_init(&schan->tasklet, chan_irqt, (unsigned long)schan);
>
> schan->irq = ret < 0 ? ret : irq;
>
> diff --git a/include/linux/dma-simple.h b/include/linux/dma-simple.h
> index 5336674..beb1489 100644
> --- a/include/linux/dma-simple.h
> +++ b/include/linux/dma-simple.h
> @@ -68,6 +68,7 @@ struct dma_simple_chan {
> int id; /* Raw id of this channel */
> int irq; /* Channel IRQ */
> enum dma_simple_pm_state pm_state;
> + struct tasklet_struct tasklet;
> };
>
> /**
> ==============
>
> Best regards,
> Yoshihiro Shimoda
>
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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