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

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Message-ID: <20200106215750.GA4341@jcrouse1-lnx.qualcomm.com>
Date:   Mon, 6 Jan 2020 14:57:51 -0700
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     smasetty@...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 Tue, Dec 24, 2019 at 08:27:28AM +0530, smasetty@...eaurora.org wrote:
> 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

This is a bug in msm_gem_address_space_create - I intended the parameter to be
the size.

Jordan

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