linux-kernel - Re: [PATCH] drm/msm: Remove pm_runtime calls from msm

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Message-ID: <20190219201135.GA20679@builder>
Date:   Tue, 19 Feb 2019 12:11:35 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Jordan Crouse <jcrouse@...eaurora.org>
Cc:     freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Sean Paul <sean@...rly.run>,
        Doug Anderson <dianders@...omium.org>,
        Kristian Kristensen <hoegsberg@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Rob Clark <robdclark@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/msm: Remove pm_runtime calls from msm_iommu.c

On Tue 19 Feb 10:48 PST 2019, Jordan Crouse wrote:

> Currently the IOMMU code calls pm_runtime_get/put on the GPU or display
> device before doing a IOMMU operation. This was because usually the
> IOMMU driver didn't do power control of its own and since the hardware
> used the same clocks and power as the respective multimedia device it
> was a easy way to make sure that the power was available.
> 
> Now two things have changed. First, the SMMU devices can do their own power
> control and more important bringing up the a6xx GPU isn't as easy as
> turning on some clocks. To bring the GPU up we need the GMU which itself
> needs the IOMMU so we have a chicken and egg problem.
> 
> Luckily this is easily fixed by removing the pm_runtime calls from the
> functions and letting the device link to the IOMMU device handle the magic.
> 
> Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>

Thanks for the patch Jordan, this resolves the previously seen splat and
the GPU driver is now happily initialized.

Tested-by: Bjorn Andersson <bjorn.andersson@...aro.org>

Regards,
Bjorn

> ---
> 
>  drivers/gpu/drm/msm/msm_iommu.c | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
> index 4d62790..12bb54c 100644
> --- a/drivers/gpu/drm/msm/msm_iommu.c
> +++ b/drivers/gpu/drm/msm/msm_iommu.c
> @@ -38,13 +38,8 @@ static int msm_iommu_attach(struct msm_mmu *mmu, const char * const *names,
>  			    int cnt)
>  {
>  	struct msm_iommu *iommu = to_msm_iommu(mmu);
> -	int ret;
>  
> -	pm_runtime_get_sync(mmu->dev);
> -	ret = iommu_attach_device(iommu->domain, mmu->dev);
> -	pm_runtime_put_sync(mmu->dev);
> -
> -	return ret;
> +	return iommu_attach_device(iommu->domain, mmu->dev);
>  }
>  
>  static void msm_iommu_detach(struct msm_mmu *mmu, const char * const *names,
> @@ -52,9 +47,7 @@ static void msm_iommu_detach(struct msm_mmu *mmu, const char * const *names,
>  {
>  	struct msm_iommu *iommu = to_msm_iommu(mmu);
>  
> -	pm_runtime_get_sync(mmu->dev);
>  	iommu_detach_device(iommu->domain, mmu->dev);
> -	pm_runtime_put_sync(mmu->dev);
>  }
>  
>  static int msm_iommu_map(struct msm_mmu *mmu, uint64_t iova,
> @@ -63,9 +56,7 @@ static int msm_iommu_map(struct msm_mmu *mmu, uint64_t iova,
>  	struct msm_iommu *iommu = to_msm_iommu(mmu);
>  	size_t ret;
>  
> -//	pm_runtime_get_sync(mmu->dev);
>  	ret = iommu_map_sg(iommu->domain, iova, sgt->sgl, sgt->nents, prot);
> -//	pm_runtime_put_sync(mmu->dev);
>  	WARN_ON(!ret);
>  
>  	return (ret == len) ? 0 : -EINVAL;
> @@ -75,9 +66,7 @@ static int msm_iommu_unmap(struct msm_mmu *mmu, uint64_t iova, unsigned len)
>  {
>  	struct msm_iommu *iommu = to_msm_iommu(mmu);
>  
> -	pm_runtime_get_sync(mmu->dev);
>  	iommu_unmap(iommu->domain, iova, len);
> -	pm_runtime_put_sync(mmu->dev);
>  
>  	return 0;
>  }
> -- 
> 2.7.4
>