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SubjectRe: [PATCH v15 12/12] of: Add plumbing for restricted DMA pool
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On 7/2/21 6:18 AM, Will Deacon wrote:
> On Fri, Jul 02, 2021 at 12:39:41PM +0100, Robin Murphy wrote:
>> On 2021-07-02 04:08, Guenter Roeck wrote:
>>> On Thu, Jun 24, 2021 at 11:55:26PM +0800, Claire Chang wrote:
>>>> If a device is not behind an IOMMU, we look up the device node and set
>>>> up the restricted DMA when the restricted-dma-pool is presented.
>>>>
>>>> Signed-off-by: Claire Chang <tientzu@chromium.org>
>>>> Tested-by: Stefano Stabellini <sstabellini@kernel.org>
>>>> Tested-by: Will Deacon <will@kernel.org>
>>>
>>> With this patch in place, all sparc and sparc64 qemu emulations
>>> fail to boot. Symptom is that the root file system is not found.
>>> Reverting this patch fixes the problem. Bisect log is attached.
>>
>> Ah, OF_ADDRESS depends on !SPARC, so of_dma_configure_id() is presumably
>> returning an unexpected -ENODEV from the of_dma_set_restricted_buffer()
>> stub. That should probably be returning 0 instead, since either way it's not
>> an error condition for it to simply do nothing.
>
> Something like below?
>

Yes, that does the trick.

> Will
>
> --->8
>
>>From 4d9dcb9210c1f37435b6088284e04b6b36ee8c4d Mon Sep 17 00:00:00 2001
> From: Will Deacon <will@kernel.org>
> Date: Fri, 2 Jul 2021 14:13:28 +0100
> Subject: [PATCH] of: Return success from of_dma_set_restricted_buffer() when
> !OF_ADDRESS
>
> When CONFIG_OF_ADDRESS=n, of_dma_set_restricted_buffer() returns -ENODEV
> and breaks the boot for sparc[64] machines. Return 0 instead, since the
> function is essentially a glorified NOP in this configuration.
>
> Cc: Claire Chang <tientzu@chromium.org>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Reported-by: Guenter Roeck <linux@roeck-us.net>
> Suggested-by: Robin Murphy <robin.murphy@arm.com>
> Link: https://lore.kernel.org/r/20210702030807.GA2685166@roeck-us.net
> Signed-off-by: Will Deacon <will@kernel.org>

Tested-by: Guenter Roeck <linux@roeck-us.net>

> ---
> drivers/of/of_private.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
> index 8fde97565d11..34dd548c5eac 100644
> --- a/drivers/of/of_private.h
> +++ b/drivers/of/of_private.h
> @@ -173,7 +173,8 @@ static inline int of_dma_get_range(struct device_node *np,
> static inline int of_dma_set_restricted_buffer(struct device *dev,
> struct device_node *np)
> {
> - return -ENODEV;
> + /* Do nothing, successfully. */
> + return 0;
> }
> #endif
>
>

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