Messages in this thread | | | Date | Wed, 11 Mar 2020 07:18:06 +0100 | From | Christoph Hellwig <> | Subject | Re: [RFC PATCH] mfd: mfd-core: inherit only valid dma_masks/flags from parent |
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On Wed, Mar 11, 2020 at 12:09:35AM +0100, Michael Walle wrote: > Only copy the dma_masks and flags from the parent device, if the parent > has a valid dma_mask/flags. Commit cdfee5623290 ("driver core: > initialize a default DMA mask for platform device") initialize the DMA > masks of a platform device. But if the parent doesn't have a dma_mask > set, for example if it's an I2C device, the dma_mask of the child > platform device will be set to zero again. Which leads to many "DMA mask > not set" warnings, if the MFD cell has the of_compatible property set. > > [ 1.877937] sl28cpld-pwm sl28cpld-pwm: DMA mask not set > [ 1.883282] sl28cpld-pwm sl28cpld-pwm.0: DMA mask not set > [ 1.888795] sl28cpld-gpio sl28cpld-gpio: DMA mask not set > > Thus a MFD child should just inherit valid dma_masks and keep the > platform default otherwise. > > Cc: Christoph Hellwig <hch@lst.de> > Cc: Rob Herring <robh@kernel.org> > Cc: Robin Murphy <robin.murphy@arm.com> > Cc: Russell King <linux@armlinux.org.uk> > Signed-off-by: Michael Walle <michael@walle.cc> > --- > > Hi, > > I don't know if that is the correct way of handling things. Maybe I'm > also doing something wrong in my driver, I had a look at other I2C MFD > drivers but couldn't find a clue why they shouldn't have the same > problem. > > There was also a thread [1] about this topic, but there seems to be no > conclusion. > > [1] https://www.spinics.net/lists/linux-renesas-soc/msg31581.html > > drivers/mfd/mfd-core.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c > index b9eb8f40c073..5d8ea5e8e93c 100644 > --- a/drivers/mfd/mfd-core.c > +++ b/drivers/mfd/mfd-core.c > @@ -139,9 +139,12 @@ static int mfd_add_device(struct device *parent, int id, > > pdev->dev.parent = parent; > pdev->dev.type = &mfd_dev_type; > - pdev->dev.dma_mask = parent->dma_mask; > - pdev->dev.dma_parms = parent->dma_parms; > - pdev->dev.coherent_dma_mask = parent->coherent_dma_mask; > + if (parent->dma_mask) > + pdev->dev.dma_mask = parent->dma_mask; > + if (parent->dma_parms) > + pdev->dev.dma_parms = parent->dma_parms;
Both of these are pointers, and we can't just share them. You need to allocate storage for them and the allocate the values over.
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