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    SubjectRe: [PATCH 1/7 v2] dmaengine: add a simple dma library
    Hi Guennadi-san,

    2012/01/27 17:48, Guennadi Liakhovetski wrote:
    > Hi Shimoda-san
    >
    > On Fri, 27 Jan 2012, Shimoda, Yoshihiro wrote:
    [ snip ]
    >>>
    >>> 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.

    Thank you for your comment.

    I investigaed the issue. I found out the renesas_usbhs driver may
    call tx_submit() in the callback() of the dma-simple finally.
    In this case, the value of power_up in the simple_tx_submit is 0,
    the start_xfer() is not called. And then, even if the ld_queue is
    not empty, the DMA doesn't start.


    So, if I add codes like the following in the dma-simple.c,
    the renesas_usbhs driver can work correctly without the driver changes.
    If you think the code is good, would you merge it to your code?
    ======= chan_irqt() =======
    simple_chan_ld_cleanup(schan, false);

    + spin_lock_irq(&schan->chan_lock);
    + /* Next desc */
    + simple_chan_xfer_ld_queue(schan);
    + spin_unlock_irq(&schan->chan_lock);

    return IRQ_HANDLED;
    ==============

    Best regards,
    Yoshihiro Shimoda

    > 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/
    >


    --
    Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
    EC No.


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