Hi Finn,
On Fri, May 11, 2018 at 11:55 AM, Finn Thain <fthain@xxxxxxxxxxxxxxxxxxx> wrote:
What's worse, if you do pass a dma_mask in struct
platform_device_info, you end up with this problem in
platform_device_register_full():
if (pdevinfo->dma_mask) {
/*
* This memory isn't freed when the device is put,
* I don't have a nice idea for that though. Conceptually
* dma_mask in struct device should not be a pointer.
* See http://thread.gmane.org/gmane.linux.kernel.pci/9081
*/
pdev->dev.dma_mask =
kmalloc(sizeof(*pdev->dev.dma_mask), GFP_KERNEL);
Maybe platform_device_register_full() should rather check whether
dev.coherent_dma_mask is set, and make dev.dma_mask point to that? This
is how we solved the warning issue for the Zorro bus devices...
(8614f1b58bd0e920a5859464a500b93152c5f8b1)
The claim in the comment above that a pointer is the wrong solution
suggests that your proposal won't get far. Also, your proposal doesn't
I read the comment to be mostly concerned about not freeing memory,
and attempted to address that. I won't pretend it's the right thing to
do if the pointer will go away anyway, and I certainly won't submit a
patch. Sorry for muddling the issue.
address the other issues I raised: a new
platform_device_register_simple_dma() API would only have two callers, and
the dma mask setup for device-tree probed platform devices is apparently a
work-in-progress (which I don't want to churn up).
Yes, and that's why I would prefer your old patch handling this in the
device driver (which Geert didn't like), or in the alternative to set
the mask up when registering a device with its bus where appropriate.
I concede this won't help with pure platform devices but as we can't
test all these, we should leave the fix for platfoem devices up to
Christoph.
With people setting the mask to kill the WARNING splat, this may
become more common.
Since the commit which introduced the WARNING, only commits f61e64310b75
("m68k: set dma and coherent masks for platform FEC ethernets") and
7bcfab202ca7 ("powerpc/macio: set a proper dma_coherent_mask") seem to be
aimed at squelching that WARNING.
(Am I missing any others?)
Zorro devices :-)
Right, I should add commit 55496d3fe2ac ("zorro: Set up z->dev.dma_mask
for the DMA API") to that list.
Which begs the question: why can' you set up all Nubus bus devices' DMA
masks in nubus_device_register(), or nubus_add_board()?
I am expecting to see the same WARNING from the nubus sonic driver but it
hasn't happened yet, so I don't have a patch for it yet. In anycase, the
nubus fix would be a lot like the zorro bus fix, so I don't see a problem.
That's odd. But what I meant to say is that by setting up
dma_coherent_mask in nubus_add_board(), and pointing dma_mask to that,
ypu won't need any patches to Nubus device drivers.
I must be missing something else...
Cheers,
Michael
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