On Thu, Aug 20, 2020 at 01:59:23PM +0200, Paul Cercueil wrote:
> Hi,
>
> Le dim. 16 août 2020 à 12:52, madhuparnabhowmik10@xxxxxxxxx a écrit :
> > From: Madhuparna Bhowmik <madhuparnabhowmik10@xxxxxxxxx>
> >
> > In probe IRQ is requested before zchan->id is initialized which can be
> > read in the irq handler. Hence, shift request irq and enable clock after
> > other initializations complete. Here, enable clock part is not part of
> > the race, it is just shifted down after request_irq to keep the error
> > path same as before.
> >
> > Found by Linux Driver Verification project (linuxtesting.org).
> >
> > Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@xxxxxxxxx>
>
> I don't think there is a race at all, the interrupt handler won't be called
> before the DMA is registered.
>
> More importantly, this patch will break things, as there are now register
> writes in the probe before the clock is enabled.
>
Okay, thanks for reviewing the patch anyway, and sorry for the trouble.
Regards,
Madhuparna
> Cheers,
> -Paul
>
> > ---
> > drivers/dma/dma-jz4780.c | 44 ++++++++++++++++++++--------------------
> > 1 file changed, 22 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
> > index 448f663da89c..5cbc8c3bd6c7 100644
> > --- a/drivers/dma/dma-jz4780.c
> > +++ b/drivers/dma/dma-jz4780.c
> > @@ -879,28 +879,6 @@ static int jz4780_dma_probe(struct platform_device
> > *pdev)
> > return -EINVAL;
> > }
> >
> > - ret = platform_get_irq(pdev, 0);
> > - if (ret < 0)
> > - return ret;
> > -
> > - jzdma->irq = ret;
> > -
> > - ret = request_irq(jzdma->irq, jz4780_dma_irq_handler, 0,
> > dev_name(dev),
> > - jzdma);
> > - if (ret) {
> > - dev_err(dev, "failed to request IRQ %u!\n", jzdma->irq);
> > - return ret;
> > - }
> > -
> > - jzdma->clk = devm_clk_get(dev, NULL);
> > - if (IS_ERR(jzdma->clk)) {
> > - dev_err(dev, "failed to get clock\n");
> > - ret = PTR_ERR(jzdma->clk);
> > - goto err_free_irq;
> > - }
> > -
> > - clk_prepare_enable(jzdma->clk);
> > -
> > /* Property is optional, if it doesn't exist the value will remain 0.
> > */
> > of_property_read_u32_index(dev->of_node, "ingenic,reserved-channels",
> > 0, &jzdma->chan_reserved);
> > @@ -949,6 +927,28 @@ static int jz4780_dma_probe(struct platform_device
> > *pdev)
> > jzchan->vchan.desc_free = jz4780_dma_desc_free;
> > }
> >
> > + ret = platform_get_irq(pdev, 0);
> > + if (ret < 0)
> > + return ret;
> > +
> > + jzdma->irq = ret;
> > +
> > + ret = request_irq(jzdma->irq, jz4780_dma_irq_handler, 0,
> > dev_name(dev),
> > + jzdma);
> > + if (ret) {
> > + dev_err(dev, "failed to request IRQ %u!\n", jzdma->irq);
> > + return ret;
> > + }
> > +
> > + jzdma->clk = devm_clk_get(dev, NULL);
> > + if (IS_ERR(jzdma->clk)) {
> > + dev_err(dev, "failed to get clock\n");
> > + ret = PTR_ERR(jzdma->clk);
> > + goto err_free_irq;
> > + }
> > +
> > + clk_prepare_enable(jzdma->clk);
> > +
> > ret = dmaenginem_async_device_register(dd);
> > if (ret) {
> > dev_err(dev, "failed to register device\n");
> > --
> > 2.17.1
> >
>
>
