Re: [RFC 09/10] drm/tegra: Add IOMMU support

Thierry Reding
2014-10-02T08:39:42Z

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On Wed, Oct 01, 2014 at 11:54:11AM -0400, Sean Paul wrote:
> On Tue, Sep 30, 2014 at 2:48 PM, Sean Paul <seanpaul-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> wrote:
> > On Thu, Jun 26, 2014 at 4:49 PM, Thierry Reding
> > <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >> From: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> >>
> >> When an IOMMU device is available on the platform bus, allocate an IOMMU
> >> domain and attach the display controllers to it. The display controllers
> >> can then scan out non-contiguous buffers by mapping them through the
> >> IOMMU.
> >>
> >
> > Hi Thierry,
> > A few comments from Stéphane and myself that came up while we were
> > reviewing this for our tree.
> >
> >> Signed-off-by: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> >> ---
> >> drivers/gpu/drm/tegra/dc.c | 21 ++++
> >> drivers/gpu/drm/tegra/drm.c | 17 ++++
> >> drivers/gpu/drm/tegra/drm.h | 3 +
> >> drivers/gpu/drm/tegra/fb.c | 16 ++-
> >> drivers/gpu/drm/tegra/gem.c | 236 +++++++++++++++++++++++++++++++++++++++-----
> >> drivers/gpu/drm/tegra/gem.h | 4 +
> >> 6 files changed, 273 insertions(+), 24 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c
> >> index afcca04f5367..0f7452d04811 100644
> >> --- a/drivers/gpu/drm/tegra/dc.c
> >> +++ b/drivers/gpu/drm/tegra/dc.c
> >> @@ -9,6 +9,7 @@
> >>
> >> #include <linux/clk.h>
> >> #include <linux/debugfs.h>
> >> +#include <linux/iommu.h>
> >> #include <linux/reset.h>
> >>
> >> #include "dc.h"
> >> @@ -1283,8 +1284,18 @@ static int tegra_dc_init(struct host1x_client *client)
> >> {
> >> struct drm_device *drm = dev_get_drvdata(client->parent);
> >> struct tegra_dc *dc = host1x_client_to_dc(client);
> >> + struct tegra_drm *tegra = drm->dev_private;
> >> int err;
> >>
> >> + if (tegra->domain) {
> >> + err = iommu_attach_device(tegra->domain, dc->dev);
> >> + if (err < 0) {
> >> + dev_err(dc->dev, "failed to attach to IOMMU: %d\n",
> >> + err);
> >> + return err;
> >> + }
> >
> > [from Stéphane]
> >
> > shouldn't we call detach in the error paths below?
> >
> >
> >> + }
> >> +
> >> drm_crtc_init(drm, &dc->base, &tegra_crtc_funcs);
> >> drm_mode_crtc_set_gamma_size(&dc->base, 256);
> >> drm_crtc_helper_add(&dc->base, &tegra_crtc_helper_funcs);
> >> @@ -1318,7 +1329,9 @@ static int tegra_dc_init(struct host1x_client *client)
> >>
> >> static int tegra_dc_exit(struct host1x_client *client)
> >> {
> >> + struct drm_device *drm = dev_get_drvdata(client->parent);
> >> struct tegra_dc *dc = host1x_client_to_dc(client);
> >> + struct tegra_drm *tegra = drm->dev_private;
> >> int err;
> >>
> >> devm_free_irq(dc->dev, dc->irq, dc);
> >> @@ -1335,6 +1348,8 @@ static int tegra_dc_exit(struct host1x_client *client)
> >> return err;
> >> }
> >>
> >> + iommu_detach_device(tegra->domain, dc->dev);
> >> +
> >> return 0;
> >> }
> >>
> >> @@ -1462,6 +1477,12 @@ static int tegra_dc_probe(struct platform_device *pdev)
> >> return -ENXIO;
> >> }
> >>
> >> + err = iommu_attach(&pdev->dev);
> >> + if (err < 0) {
> >> + dev_err(&pdev->dev, "failed to attach to IOMMU: %d\n", err);
> >> + return err;
> >> + }
> >> +
> >> INIT_LIST_HEAD(&dc->client.list);
> >> dc->client.ops = &dc_client_ops;
> >> dc->client.dev = &pdev->dev;
> >> diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
> >> index 59736bb810cd..1d2bbafad982 100644
> >> --- a/drivers/gpu/drm/tegra/drm.c
> >> +++ b/drivers/gpu/drm/tegra/drm.c
> >> @@ -8,6 +8,7 @@
> >> */
> >>
> >> #include <linux/host1x.h>
> >> +#include <linux/iommu.h>
> >>
> >> #include "drm.h"
> >> #include "gem.h"
> >> @@ -33,6 +34,16 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
> >> if (!tegra)
> >> return -ENOMEM;
> >>
> >> + if (iommu_present(&platform_bus_type)) {
> >> + tegra->domain = iommu_domain_alloc(&platform_bus_type);
> >> + if (IS_ERR(tegra->domain)) {
> >> + kfree(tegra);
> >> + return PTR_ERR(tegra->domain);
> >> + }
> >> +
> >> + drm_mm_init(&tegra->mm, 0, SZ_2G);
> >
> >
> > [from Stéphane]:
> >
> > none of these are freed in the error path below (iommu_domain_free and
> > drm_mm_takedown)
> >
> > also |tegra| isn't freed either?
> >
> >
> >
> >> + }
> >> +
> >> mutex_init(&tegra->clients_lock);
> >> INIT_LIST_HEAD(&tegra->clients);
> >> drm->dev_private = tegra;
> >> @@ -71,6 +82,7 @@ static int tegra_drm_load(struct drm_device *drm, unsigned long flags)
> >> static int tegra_drm_unload(struct drm_device *drm)
> >> {
> >> struct host1x_device *device = to_host1x_device(drm->dev);
> >> + struct tegra_drm *tegra = drm->dev_private;
> >> int err;
> >>
> >> drm_kms_helper_poll_fini(drm);
> >> @@ -82,6 +94,11 @@ static int tegra_drm_unload(struct drm_device *drm)
> >> if (err < 0)
> >> return err;
> >>
> >> + if (tegra->domain) {
> >> + iommu_domain_free(tegra->domain);
> >> + drm_mm_takedown(&tegra->mm);
> >> + }
> >> +
> >> return 0;
> >> }
> >>
> >> diff --git a/drivers/gpu/drm/tegra/drm.h b/drivers/gpu/drm/tegra/drm.h
> >> index 96d754e7b3eb..a07c796b7edc 100644
> >> --- a/drivers/gpu/drm/tegra/drm.h
> >> +++ b/drivers/gpu/drm/tegra/drm.h
> >> @@ -39,6 +39,9 @@ struct tegra_fbdev {
> >> struct tegra_drm {
> >> struct drm_device *drm;
> >>
> >> + struct iommu_domain *domain;
> >> + struct drm_mm mm;
> >> +
> >> struct mutex clients_lock;
> >> struct list_head clients;
> >>
> >> diff --git a/drivers/gpu/drm/tegra/fb.c b/drivers/gpu/drm/tegra/fb.c
> >> index 7790d43ad082..21c65dd817c3 100644
> >> --- a/drivers/gpu/drm/tegra/fb.c
> >> +++ b/drivers/gpu/drm/tegra/fb.c
> >> @@ -65,8 +65,12 @@ static void tegra_fb_destroy(struct drm_framebuffer *framebuffer)
> >> for (i = 0; i < fb->num_planes; i++) {
> >> struct tegra_bo *bo = fb->planes[i];
> >>
> >> - if (bo)
> >> + if (bo) {
> >> + if (bo->pages && bo->virt)
> >> + vunmap(bo->virt);
> >> +
> >> drm_gem_object_unreference_unlocked(&bo->gem);
> >> + }
> >> }
> >>
> >> drm_framebuffer_cleanup(framebuffer);
> >> @@ -252,6 +256,16 @@ static int tegra_fbdev_probe(struct drm_fb_helper *helper,
> >> offset = info->var.xoffset * bytes_per_pixel +
> >> info->var.yoffset * fb->pitches[0];
> >>
> >> + if (bo->pages) {
> >> + bo->vaddr = vmap(bo->pages, bo->num_pages, VM_MAP,
> >> + pgprot_writecombine(PAGE_KERNEL));
> >> + if (!bo->vaddr) {
> >> + dev_err(drm->dev, "failed to vmap() framebuffer\n");
> >> + err = -ENOMEM;
> >> + goto destroy;
> >> + }
> >> + }
> >> +
> >> drm->mode_config.fb_base = (resource_size_t)bo->paddr;
> >> info->screen_base = (void __iomem *)bo->vaddr + offset;
> >> info->screen_size = size;
> >> diff --git a/drivers/gpu/drm/tegra/gem.c b/drivers/gpu/drm/tegra/gem.c
> >> index c1e4e8b6e5ca..2912e61a2599 100644
> >> --- a/drivers/gpu/drm/tegra/gem.c
> >> +++ b/drivers/gpu/drm/tegra/gem.c
> >> @@ -14,8 +14,10 @@
> >> */
> >>
> >> #include <linux/dma-buf.h>
> >> +#include <linux/iommu.h>
> >> #include <drm/tegra_drm.h>
> >>
> >> +#include "drm.h"
> >> #include "gem.h"
> >>
> >> static inline struct tegra_bo *host1x_to_tegra_bo(struct host1x_bo *bo)
> >> @@ -90,14 +92,144 @@ static const struct host1x_bo_ops tegra_bo_ops = {
> >> .kunmap = tegra_bo_kunmap,
> >> };
> >>
> >> +static int iommu_map_sg(struct iommu_domain *domain, struct sg_table *sgt,
> >> + dma_addr_t iova, int prot)
> >> +{
> >> + unsigned long offset = 0;
> >> + struct scatterlist *sg;
> >> + unsigned int i, j;
> >> + int err;
> >> +
> >> + for_each_sg(sgt->sgl, sg, sgt->nents, i) {
> >> + dma_addr_t phys = sg_phys(sg);
> >> + size_t length = sg->offset;
> >> +
> >> + phys = sg_phys(sg) - sg->offset;
> >> + length = sg->length + sg->offset;
> >> +
> >> + err = iommu_map(domain, iova + offset, phys, length, prot);
> >> + if (err < 0)
> >> + goto unmap;
> >> +
> >> + offset += length;
> >> + }
> >> +
> >> + return 0;
> >> +
> >> +unmap:
> >> + offset = 0;
> >> +
> >> + for_each_sg(sgt->sgl, sg, i, j) {
> >> + size_t length = sg->length + sg->offset;
> >> + iommu_unmap(domain, iova + offset, length);
> >> + offset += length;
> >> + }
> >> +
> >> + return err;
> >> +}
> >> +
> >> +static int iommu_unmap_sg(struct iommu_domain *domain, struct sg_table *sgt,
> >> + dma_addr_t iova)
> >> +{
> >> + unsigned long offset = 0;
> >> + struct scatterlist *sg;
> >> + unsigned int i;
> >> +
> >> + for_each_sg(sgt->sgl, sg, sgt->nents, i) {
> >> + dma_addr_t phys = sg_phys(sg);
> >> + size_t length = sg->offset;
> >> +
> >> + phys = sg_phys(sg) - sg->offset;
> >> + length = sg->length + sg->offset;
> >> +
> >> + iommu_unmap(domain, iova + offset, length);
> >> + offset += length;
> >> + }
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static int tegra_bo_iommu_map(struct tegra_drm *tegra, struct tegra_bo *bo)
> >> +{
> >> + int prot = IOMMU_READ | IOMMU_WRITE;
> >> + int err;
> >> +
> >> + if (bo->mm)
> >> + return -EBUSY;
> >> +
> >> + bo->mm = kzalloc(sizeof(*bo->mm), GFP_KERNEL);
> >> + if (!bo->mm)
> >> + return -ENOMEM;
> >> +
> >> + err = drm_mm_insert_node_generic(&tegra->mm, bo->mm, bo->gem.size,
> >> + PAGE_SIZE, 0, 0, 0);
> >> + if (err < 0) {
> >> + dev_err(tegra->drm->dev, "out of virtual memory: %d\n", err);
> >> + return err;
> >> + }
> >> +
> >> + bo->paddr = bo->mm->start;
> >> +
> >> + err = iommu_map_sg(tegra->domain, bo->sgt, bo->paddr, prot);
> >> + if (err < 0) {
> >> + dev_err(tegra->drm->dev, "failed to map buffer: %d\n", err);
> >> + return err;
> >> + }
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static int tegra_bo_iommu_unmap(struct tegra_drm *tegra, struct tegra_bo *bo)
> >> +{
> >> + if (!bo->mm)
> >> + return 0;
> >> +
> >> + iommu_unmap_sg(tegra->domain, bo->sgt, bo->paddr);
> >> + drm_mm_remove_node(bo->mm);
> >> +
> >> + kfree(bo->mm);
> >> + return 0;
> >> +}
> >> +
> >> static void tegra_bo_destroy(struct drm_device *drm, struct tegra_bo *bo)
> >> {
> >> - dma_free_writecombine(drm->dev, bo->gem.size, bo->vaddr, bo->paddr);
> >> + if (!bo->pages)
> >> + dma_free_writecombine(drm->dev, bo->gem.size, bo->vaddr,
> >> + bo->paddr);
>
> One more thing. If tegra_bo_alloc fails, we'll have bo->vaddr == NULL
> and bo->paddr == ~0 here, which causes a crash.
>
> I posted https://lkml.org/lkml/2014/9/30/659 to check for the error
> condition in the mm code, but it seems like reviewer consensus is to
> check for this before calling free.
>
> As such, we'll need to make sure bo->vaddr != NULL before calling
> dma_free_writecombine to avoid this situation.
>
> Would you prefer I send a patch up to fix this separately, or would
> you like to roll this into your next version?

Thanks for pointing all of these out. I'm going to trace the failure
code path anyway since there seem to be a couple of loose ends here and
there, so I'll probably roll in a fix for this anyway.

Thierry

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