linux-kernel - Re: [PATCH v3 5/5] drm/msm/a6xx: Support split pagetables

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Message-ID: <8aec2a4f74fede1cf616b9e2eece3e8e@codeaurora.org>
Date:   Tue, 24 Dec 2019 08:27:28 +0530
From:   smasetty@...eaurora.org
To:     Jordan Crouse <jcrouse@...eaurora.org>
Cc:     iommu@...ts.linux-foundation.org, freedreno@...ts.freedesktop.org,
        David Airlie <airlied@...ux.ie>, will@...nel.org,
        robin.murphy@....com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        Sean Paul <sean@...rly.run>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 5/5] drm/msm/a6xx: Support split pagetables

On 2019-12-16 22:07, Jordan Crouse wrote:
> Attempt to enable split pagetables if the arm-smmu driver supports it.
> This will move the default address space from the default region to
> the address range assigned to TTBR1. The behavior should be transparent
> to the driver for now but it gets the default buffers out of the way
> when we want to start swapping TTBR0 for context-specific pagetables.
> 
> Signed-off-by: Jordan Crouse <jcrouse@...eaurora.org>
> ---
> 
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 52 
> ++++++++++++++++++++++++++++++++++-
>  1 file changed, 51 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 5dc0b2c..1c6da93 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -811,6 +811,56 @@ static unsigned long a6xx_gpu_busy(struct msm_gpu 
> *gpu)
>  	return (unsigned long)busy_time;
>  }
> 
> +static struct msm_gem_address_space *
> +a6xx_create_address_space(struct msm_gpu *gpu, struct platform_device 
> *pdev)
> +{
> +	struct iommu_domain *iommu = iommu_domain_alloc(&platform_bus_type);
> +	struct msm_gem_address_space *aspace;
> +	struct msm_mmu *mmu;
> +	u64 start, size;
> +	u32 val = 1;
> +	int ret;
> +
> +	if (!iommu)
> +		return ERR_PTR(-ENOMEM);
> +
> +	/*
> +	 * Try to request split pagetables - the request has to be made 
> before
> +	 * the domian is attached
> +	 */
> +	iommu_domain_set_attr(iommu, DOMAIN_ATTR_SPLIT_TABLES, &val);
> +
> +	mmu = msm_iommu_new(&pdev->dev, iommu);
> +	if (IS_ERR(mmu)) {
> +		iommu_domain_free(iommu);
> +		return ERR_CAST(mmu);
> +	}
> +
> +	/*
> +	 * After the domain is attached, see if the split tables were 
> actually
> +	 * successful.
> +	 */
> +	ret = iommu_domain_get_attr(iommu, DOMAIN_ATTR_SPLIT_TABLES, &val);
> +	if (!ret && val) {
> +		/*
> +		 * The aperture start will be at the beginning of the TTBR1
> +		 * space so use that as a base
> +		 */
> +		start = iommu->geometry.aperture_start;
> +		size = 0xffffffff;
This should be the va_end and not the size
> +	} else {
> +		/* Otherwise use the legacy 32 bit region */
> +		start = SZ_16M;
> +		size = 0xffffffff - SZ_16M;
same as above
> +	}
> +
> +	aspace = msm_gem_address_space_create(mmu, "gpu", start, size);
> +	if (IS_ERR(aspace))
> +		iommu_domain_free(iommu);
> +
> +	return aspace;
> +}
> +
>  static const struct adreno_gpu_funcs funcs = {
>  	.base = {
>  		.get_param = adreno_get_param,
> @@ -832,7 +882,7 @@ static const struct adreno_gpu_funcs funcs = {
>  #if defined(CONFIG_DRM_MSM_GPU_STATE)
>  		.gpu_state_get = a6xx_gpu_state_get,
>  		.gpu_state_put = a6xx_gpu_state_put,
> -		.create_address_space = adreno_iommu_create_address_space,
> +		.create_address_space = a6xx_create_address_space,
>  #endif
>  	},
>  	.get_timestamp = a6xx_get_timestamp,