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drm/tegra: Reuse IOVA mapping where possible

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This partially reverts the DMA API support that was recently merged
because it was causing performance regressions on older Tegra devices.
Unfortunately, the cache maintenance performed by dma_map_sg() and
dma_unmap_sg() causes performance to drop by a factor of 10.

The right solution for this would be to cache mappings for buffers per
consumer device, but that's a bit involved. Instead, we simply revert to
the old behaviour of sharing IOVA mappings when we know that devices can
do so (i.e. they share the same IOMMU domain).

Cc: <stable@vger.kernel.org> # v5.5
Reported-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
This commit is contained in:
Thierry Reding 2020-02-04 14:59:25 +01:00
parent 2d9384ff91
commit 273da5a046
3 changed files with 63 additions and 23 deletions
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10
drivers/gpu/drm/tegra/gem.c
View File

@ -60,8 +60,16 @@ static struct sg_table *tegra_bo_pin(struct device *dev, struct host1x_bo *bo,
/*
* If we've manually mapped the buffer object through the IOMMU, make
* sure to return the IOVA address of our mapping.
*
* Similarly, for buffers that have been allocated by the DMA API the
* physical address can be used for devices that are not attached to
* an IOMMU. For these devices, callers must pass a valid pointer via
* the @phys argument.
*
* Imported buffers were also already mapped at import time, so the
* existing mapping can be reused.
*/
if (phys && obj->mm) {
if (phys) {
*phys = obj->iova;
return NULL;
}

44
drivers/gpu/drm/tegra/plane.c
View File

@ -3,6 +3,8 @@
* Copyright (C) 2017 NVIDIA CORPORATION. All rights reserved.
*/
#include <linux/iommu.h>
#include <drm/drm_atomic.h>
#include <drm/drm_atomic_helper.h>
#include <drm/drm_fourcc.h>
@ -107,21 +109,27 @@ const struct drm_plane_funcs tegra_plane_funcs = {
static int tegra_dc_pin(struct tegra_dc *dc, struct tegra_plane_state *state)
{
struct iommu_domain *domain = iommu_get_domain_for_dev(dc->dev);
unsigned int i;
int err;
for (i = 0; i < state->base.fb->format->num_planes; i++) {
struct tegra_bo *bo = tegra_fb_get_plane(state->base.fb, i);
dma_addr_t phys_addr, *phys;
struct sg_table *sgt;
if (!dc->client.group) {
struct sg_table *sgt;
if (!domain || dc->client.group)
phys = &phys_addr;
else
phys = NULL;
sgt = host1x_bo_pin(dc->dev, &bo->base, NULL);
if (IS_ERR(sgt)) {
err = PTR_ERR(sgt);
goto unpin;
}
sgt = host1x_bo_pin(dc->dev, &bo->base, phys);
if (IS_ERR(sgt)) {
err = PTR_ERR(sgt);
goto unpin;
}
if (sgt) {
err = dma_map_sg(dc->dev, sgt->sgl, sgt->nents,
DMA_TO_DEVICE);
if (err == 0) {
@ -143,7 +151,7 @@ static int tegra_dc_pin(struct tegra_dc *dc, struct tegra_plane_state *state)
state->iova[i] = sg_dma_address(sgt->sgl);
state->sgt[i] = sgt;
} else {
state->iova[i] = bo->iova;
state->iova[i] = phys_addr;
}
}
@ -156,9 +164,11 @@ static int tegra_dc_pin(struct tegra_dc *dc, struct tegra_plane_state *state)
struct tegra_bo *bo = tegra_fb_get_plane(state->base.fb, i);
struct sg_table *sgt = state->sgt[i];
dma_unmap_sg(dc->dev, sgt->sgl, sgt->nents, DMA_TO_DEVICE);
host1x_bo_unpin(dc->dev, &bo->base, sgt);
if (sgt)
dma_unmap_sg(dc->dev, sgt->sgl, sgt->nents,
DMA_TO_DEVICE);
host1x_bo_unpin(dc->dev, &bo->base, sgt);
state->iova[i] = DMA_MAPPING_ERROR;
state->sgt[i] = NULL;
}
@ -172,17 +182,13 @@ static void tegra_dc_unpin(struct tegra_dc *dc, struct tegra_plane_state *state)
for (i = 0; i < state->base.fb->format->num_planes; i++) {
struct tegra_bo *bo = tegra_fb_get_plane(state->base.fb, i);
struct sg_table *sgt = state->sgt[i];
if (!dc->client.group) {
struct sg_table *sgt = state->sgt[i];
if (sgt) {
dma_unmap_sg(dc->dev, sgt->sgl, sgt->nents,
DMA_TO_DEVICE);
host1x_bo_unpin(dc->dev, &bo->base, sgt);
}
}
if (sgt)
dma_unmap_sg(dc->dev, sgt->sgl, sgt->nents,
DMA_TO_DEVICE);
host1x_bo_unpin(dc->dev, &bo->base, sgt);
state->iova[i] = DMA_MAPPING_ERROR;
state->sgt[i] = NULL;
}

32
drivers/gpu/host1x/job.c
View File

@ -8,6 +8,7 @@
#include <linux/dma-mapping.h>
#include <linux/err.h>
#include <linux/host1x.h>
#include <linux/iommu.h>
#include <linux/kref.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
@ -101,9 +102,11 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
{
struct host1x_client *client = job->client;
struct device *dev = client->dev;
struct iommu_domain *domain;
unsigned int i;
int err;
domain = iommu_get_domain_for_dev(dev);
job->num_unpins = 0;
for (i = 0; i < job->num_relocs; i++) {
@ -117,7 +120,19 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
goto unpin;
}
if (client->group)
/*
* If the client device is not attached to an IOMMU, the
* physical address of the buffer object can be used.
*
* Similarly, when an IOMMU domain is shared between all
* host1x clients, the IOVA is already available, so no
* need to map the buffer object again.
*
* XXX Note that this isn't always safe to do because it
* relies on an assumption that no cache maintenance is
* needed on the buffer objects.
*/
if (!domain || client->group)
phys = &phys_addr;
else
phys = NULL;
@ -176,6 +191,7 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
dma_addr_t phys_addr;
unsigned long shift;
struct iova *alloc;
dma_addr_t *phys;
unsigned int j;
g->bo = host1x_bo_get(g->bo);
@ -184,7 +200,17 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
goto unpin;
}
sgt = host1x_bo_pin(host->dev, g->bo, NULL);
/**
* If the host1x is not attached to an IOMMU, there is no need
* to map the buffer object for the host1x, since the physical
* address can simply be used.
*/
if (!iommu_get_domain_for_dev(host->dev))
phys = &phys_addr;
else
phys = NULL;
sgt = host1x_bo_pin(host->dev, g->bo, phys);
if (IS_ERR(sgt)) {
err = PTR_ERR(sgt);
goto unpin;
@ -214,7 +240,7 @@ static unsigned int pin_job(struct host1x *host, struct host1x_job *job)
job->unpins[job->num_unpins].size = gather_size;
phys_addr = iova_dma_addr(&host->iova, alloc);
} else {
} else if (sgt) {
err = dma_map_sg(host->dev, sgt->sgl, sgt->nents,
DMA_TO_DEVICE);
if (!err) {