linux-kernel - Re: [PATCH] gpu: host1x: Free the IOMMU domain when there is no device to attach

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Date:   Tue, 11 Jul 2017 20:09:56 +0300
From:   Mikko Perttunen <cyndis@...si.fi>
To:     Paul Kocialkowski <contact@...lk.fr>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Cc:     "jonathanh@...dia.com" <jonathanh@...dia.com>,
        "mperttunen@...dia.com" <mperttunen@...dia.com>,
        "treding@...dia.com" <treding@...dia.com>,
        "swarren@...dia.com" <swarren@...dia.com>
Subject: Re: [PATCH] gpu: host1x: Free the IOMMU domain when there is no
 device to attach

On 07/11/2017 05:44 PM, Paul Kocialkowski wrote:
> On Tue, 2017-07-11 at 14:37 +0000, Marcel Ziswiler wrote:
>> On Tue, 2017-07-11 at 11:49 +0300, Paul Kocialkowski wrote:
>>> On Mon, 2017-07-10 at 21:33 +0200, Paul Kocialkowski wrote:
>>>> When there is no device to attach to the IOMMU domain, as may be
>>>> the
>>>> case when the device-tree does not contain the proper iommu node,
>>>> it
>>>> is
>>>> best to keep going without IOMMU support rather than failing.
>>>> This allows the driver to probe and function instead of taking
>>>> down
>>>> all of the tegra drm driver, leading to missing display support.
>>>
>>> Fixes: 404bfb78daf3 ("gpu: host1x: Add IOMMU support")
>>>
>>>> Signed-off-by: Paul Kocialkowski <contact-W9ppeneeCTY@...lic.gmane
>>>> .
>>>> org>
>>>> ---
>>>>   drivers/gpu/host1x/dev.c | 8 +++++++-
>>>>   1 file changed, 7 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/host1x/dev.c b/drivers/gpu/host1x/dev.c
>>>> index ac65f52850a6..f296738d0de8 100644
>>>> --- a/drivers/gpu/host1x/dev.c
>>>> +++ b/drivers/gpu/host1x/dev.c
>>>> @@ -186,8 +186,13 @@ static int host1x_probe(struct
>>>> platform_device
>>>> *pdev)
>>>>   			return -ENOMEM;
>>>>   
>>>>   		err = iommu_attach_device(host->domain, &pdev-
>>>>> dev);
>>>>
>>>> -		if (err)
>>>> +		if (err == -ENODEV) {
>>>> +			iommu_domain_free(host->domain);
>>>> +			host->domain = NULL;
>>>> +			goto iommu_skip;
>>>> +		} else if (err) {
>>>>   			goto fail_free_domain;
>>>> +		}
>>>>   
>>>>   		geometry = &host->domain->geometry;
>>>>   
>>>> @@ -198,6 +203,7 @@ static int host1x_probe(struct platform_device
>>>> *pdev)
>>>>   		host->iova_end = geometry->aperture_end;
>>>>   	}
>>>>   
>>>> +iommu_skip:
>>>>   	err = host1x_channel_list_init(host);
>>>>   	if (err) {
>>>>   		dev_err(&pdev->dev, "failed to initialize channel
>>>> list\n");
>>
>> Please note that this does no longer cleanly apply after Mikko's 'gpu:
>> host1x: Refactor channel allocation code' commit from June 15 already
>> applied to current -next. Other than that
> 
> Good to know! I intended this patch for fixing 4.12 stable, so I'm not
> even entirely sure it should land in next. The patch that fixes the
> device-tree to actually enable the iommu should be merged in priority.
> 
> If that is the case and anyone wants this patch rebased to next, feel
> free to let me know and I'll send a rebased version.

We should definitely have this for non-stable kernels too - it would be 
a bit strange if the driver worked if IOMMU support wasn't built into 
the kernel but failed if it was :) It can also be helpful for debugging 
to be able to disable IOMMU just for host1x.

> 
>> Tested-by: Marcel Ziswiler <marcel.ziswiler@...adex.com>
>> Tested-on: Apalis TK1, Apalis T30, Beaver, Colibri T30, Jetson-TK1
>>
>> Finally graphics working again, thanks guys!
> 
> Yay! :)
>