Re: [RFC PATCH powerpc] Fix a dma_mask issue of vio
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2013-11-20 01:28:36
On Tue, 2013-11-19 at 16:11 +0800, Li Zhong wrote:
I encountered following issue: [ 0.283035] ibmvscsi 30000015: couldn't initialize event pool [ 5.688822] ibmvscsi: probe of 30000015 failed with error -1 which prevents the storage from being recognized, and the machine from booting. After some digging, it seems that it is caused by commit 4886c399da as dma_mask pointer in viodev->dev is not set, so in dma_set_mask_and_coherent(), dma_set_coherent_mask() is not called because dma_set_mask(), which is dma_set_mask_pSeriesLP() returned EIO. While before the commit, dma_set_coherent_mask() is always called. I tried to replace dma_set_mask_and_coherent() with dma_coerce_mask_and_coherent(), and the machine could boot again. But I'm not sure whether this is the correct fix...
Russell, care to chime in ? I can't make sense of the semantics...
The original commit was fairly clear:
<<
Replace the following sequence:
dma_set_mask(dev, mask);
dma_set_coherent_mask(dev, mask);
with a call to the new helper dma_set_mask_and_coherent().quoted
It all makes sense so far ... but doesn't work for some odd reason, and the "fix" uses a function whose name doesn't make much sense to me ... what is the difference between "setting" and "coercing" the mask ? And why doe replacing two "set" with a "set both" doesn't work and require a coerce ? I'm asking because I'm worried about breakage elsewhere... Cheers, Ben.
quoted hunk ↗ jump to hunk
--- arch/powerpc/kernel/vio.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)diff --git a/arch/powerpc/kernel/vio.c b/arch/powerpc/kernel/vio.c index e7d0c88..76a6482 100644 --- a/arch/powerpc/kernel/vio.c +++ b/arch/powerpc/kernel/vio.c@@ -1419,7 +1419,7 @@ struct vio_dev *vio_register_device_node(struct device_node *of_node) /* needed to ensure proper operation of coherent allocations * later, in case driver doesn't set it explicitly */ - dma_set_mask_and_coherent(&viodev->dev, DMA_BIT_MASK(64)); + dma_coerce_mask_and_coherent(&viodev->dev, DMA_BIT_MASK(64)); } /* register with generic device framework */