linux-kernel - Re: [PATCH] media: staging: tegra-vde: Disable building with COMPILE

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Message-ID: <3ce3b6ed-86d3-55ac-462d-4bc91b7d04ed@huawei.com>
Date:   Fri, 6 Sep 2019 22:28:58 +0800
From:   Yuehaibing <yuehaibing@...wei.com>
To:     Dmitry Osipenko <digetx@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>
CC:     <mchehab@...nel.org>, <gregkh@...uxfoundation.org>,
        <jonathanh@...dia.com>, <robin.murphy@....com>,
        <linux-media@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <devel@...verdev.osuosl.org>, <linux-kernel@...r.kernel.org>,
        <iommu@...ts.linux-foundation.org>
Subject: Re: [PATCH] media: staging: tegra-vde: Disable building with
 COMPILE_TEST



On 2019/9/6 21:38, Dmitry Osipenko wrote:
> 29.08.2019 18:49, Thierry Reding пишет:
>> On Thu, Aug 29, 2019 at 04:58:22PM +0300, Dmitry Osipenko wrote:
>>> 29.08.2019 15:40, Thierry Reding пишет:
>>>> On Thu, Aug 29, 2019 at 01:39:32PM +0200, Hans Verkuil wrote:
>>>>> On 8/26/19 3:31 PM, YueHaibing wrote:
>>>>>> If COMPILE_TEST is y and IOMMU_SUPPORT is n, selecting TEGRA_VDE
>>>>>> to m will set IOMMU_IOVA to m, this fails the building of
>>>>>> TEGRA_HOST1X and DRM_TEGRA which is y like this:
>>>>>>
>>>>>> drivers/gpu/host1x/cdma.o: In function `host1x_cdma_init':
>>>>>> cdma.c:(.text+0x66c): undefined reference to `alloc_iova'
>>>>>> cdma.c:(.text+0x698): undefined reference to `__free_iova'
>>>>>>
>>>>>> drivers/gpu/drm/tegra/drm.o: In function `tegra_drm_unload':
>>>>>> drm.c:(.text+0xeb0): undefined reference to `put_iova_domain'
>>>>>> drm.c:(.text+0xeb4): undefined reference to `iova_cache_put'
>>>>>>
>>>>>> Reported-by: Hulk Robot <hulkci@...wei.com>
>>>>>> Fixes: 6b2265975239 ("media: staging: tegra-vde: Fix build error")
>>>>>> Fixes: b301f8de1925 ("media: staging: media: tegra-vde: Add IOMMU support")
>>>>>> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
>>>>>> ---
>>>>>>  drivers/staging/media/tegra-vde/Kconfig | 4 ++--
>>>>>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/staging/media/tegra-vde/Kconfig b/drivers/staging/media/tegra-vde/Kconfig
>>>>>> index ba49ea5..a41d30c 100644
>>>>>> --- a/drivers/staging/media/tegra-vde/Kconfig
>>>>>> +++ b/drivers/staging/media/tegra-vde/Kconfig
>>>>>> @@ -1,9 +1,9 @@
>>>>>>  # SPDX-License-Identifier: GPL-2.0
>>>>>>  config TEGRA_VDE
>>>>>>  	tristate "NVIDIA Tegra Video Decoder Engine driver"
>>>>>> -	depends on ARCH_TEGRA || COMPILE_TEST
>>>>>> +	depends on ARCH_TEGRA
>>>>>
>>>>> What happens if you drop this change,
>>>>>
>>>>>>  	select DMA_SHARED_BUFFER
>>>>>> -	select IOMMU_IOVA if (IOMMU_SUPPORT || COMPILE_TEST)
>>>>>> +	select IOMMU_IOVA if IOMMU_SUPPORT
>>>>>
>>>>> but keep this change?
>>>>>
>>>>> iova.h has stubs that are used if IOMMU_IOVA is not set, so it should
>>>>> work when compile testing this tegra-vde driver.
>>>>>
>>>>> Haven't tried it, but making sure that compile testing keep working is
>>>>> really important.
>>>
>>> The driver's code compilation works okay, it's the linkage stage which
>>> fails during compile-testing.
>>>
>>>> Yeah, that variant seems to work for me. I think it's also more correct
>>>> because the IOMMU_IOVA if IOMMU_SUPPORT dependency really says that the
>>>> IOVA usage is bound to IOMMU support. If IOMMU support is not enabled,
>>>> then IOVA is not needed either, so the dummies will do just fine.
>>>
>>> Am I understanding correctly that you're suggesting to revert [1][2] and
>>> get back to the other problem?
>>>
>>> [1]
>>> https://lore.kernel.org/linux-media/dd547b44-7abb-371f-aeee-a82b96f824e2@gmail.com/T/
>>> [2] https://patchwork.ozlabs.org/patch/1136619/
>>>
>>> If we want to keep compile testing, I guess the only reasonable variant
>>> right now is to select IOMMU_IOVA unconditionally in all of the drivers
>>> (vde, host1x, drm and etc) and then just ignore that IOVA will be
>>> compiled-and-unused if IOMMU_SUPPORT=n (note that IOMMU_SUPPORT=y in all
>>> of default kernel configurations).
>>
>> Agreed. I think we should just select IOMMU_IOVA unconditionally. We
>> really do want IOMMU_SUPPORT always as well, but it might be nice to be
>> able to switch it off for testing or so. In the cases that really matter
>> we will be enabling both IOMMU_SUPPORT and IOMMU_IOVA anyway, so might
>> as well select IOMMU_IOVA always. It's not terribly big and I can't
>> imagine anyone wanting to run a kernel without IOMMU_SUPPORT for
>> anything other than testing.
> 
> Hello Yue,
> 
> Could you please make an updated version of the fix in accordance to the above comments?
> 
> Alternatively, we can go with the current patch and temporarily remove the compile-testing. I'll make
> patches to properly re-add compile-testing sometime later then.

I prefer to do this choice, thanks.

> 
> .
>