linux-kernel - [PATCH] drm/mediatek: make imported PRIME buffers contiguous

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Message-Id: <20190723053421.179679-1-acourbot@chromium.org>
Date:   Tue, 23 Jul 2019 14:34:21 +0900
From:   Alexandre Courbot <acourbot@...omium.org>
To:     CK Hu <ck.hu@...iatek.com>, Philipp Zabel <p.zabel@...gutronix.de>,
        Tomasz Figa <tfiga@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Matthias Brugger <matthias.bgg@...il.com>
Cc:     dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Alexandre Courbot <acourbot@...omium.org>
Subject: [PATCH] drm/mediatek: make imported PRIME buffers contiguous

This driver requires imported PRIME buffers to appear contiguously in
its IO address space. Make sure this is the case by setting the maximum
DMA segment size to a better value than the default 64K on the DMA
device, and use said DMA device when importing PRIME buffers.

Signed-off-by: Alexandre Courbot <acourbot@...omium.org>
---
 drivers/gpu/drm/mediatek/mtk_drm_drv.c | 47 ++++++++++++++++++++++++--
 drivers/gpu/drm/mediatek/mtk_drm_drv.h |  2 ++
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index 95fdbd0fbcac..4ad4770fab13 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -213,6 +213,7 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 	struct mtk_drm_private *private = drm->dev_private;
 	struct platform_device *pdev;
 	struct device_node *np;
+	struct device *dma_dev;
 	int ret;
 
 	if (!iommu_present(&platform_bus_type))
@@ -275,7 +276,27 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 		goto err_component_unbind;
 	}
 
-	private->dma_dev = &pdev->dev;
+	dma_dev = &pdev->dev;
+	private->dma_dev = dma_dev;
+
+	/*
+	 * Configure the DMA segment size to make sure we get contiguous IOVA
+	 * when importing PRIME buffers.
+	 */
+	if (!dma_dev->dma_parms) {
+		private->dma_parms_allocated = true;
+		dma_dev->dma_parms =
+			devm_kzalloc(drm->dev, sizeof(*dma_dev->dma_parms),
+				     GFP_KERNEL);
+	}
+	if (!dma_dev->dma_parms)
+		goto err_component_unbind;
+
+	ret = dma_set_max_seg_size(dma_dev, (unsigned int)DMA_BIT_MASK(32));
+	if (ret) {
+		dev_err(dma_dev, "Failed to set DMA segment size\n");
+		goto err_unset_dma_parms;
+	}
 
 	/*
 	 * We don't use the drm_irq_install() helpers provided by the DRM
@@ -285,13 +306,16 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 	drm->irq_enabled = true;
 	ret = drm_vblank_init(drm, MAX_CRTC);
 	if (ret < 0)
-		goto err_component_unbind;
+		goto err_unset_dma_parms;
 
 	drm_kms_helper_poll_init(drm);
 	drm_mode_config_reset(drm);
 
 	return 0;
 
+err_unset_dma_parms:
+	if (private->dma_parms_allocated)
+		dma_dev->dma_parms = NULL;
 err_component_unbind:
 	component_unbind_all(drm->dev, drm);
 err_config_cleanup:
@@ -302,9 +326,14 @@ static int mtk_drm_kms_init(struct drm_device *drm)
 
 static void mtk_drm_kms_deinit(struct drm_device *drm)
 {
+	struct mtk_drm_private *private = drm->dev_private;
+
 	drm_kms_helper_poll_fini(drm);
 	drm_atomic_helper_shutdown(drm);
 
+	if (private->dma_parms_allocated)
+		private->dma_dev->dma_parms = NULL;
+
 	component_unbind_all(drm->dev, drm);
 	drm_mode_config_cleanup(drm);
 }
@@ -320,6 +349,18 @@ static const struct file_operations mtk_drm_fops = {
 	.compat_ioctl = drm_compat_ioctl,
 };
 
+/*
+ * We need to override this because the device used to import the memory is
+ * not dev->dev, as drm_gem_prime_import() expects.
+ */
+struct drm_gem_object *mtk_drm_gem_prime_import(struct drm_device *dev,
+						struct dma_buf *dma_buf)
+{
+	struct mtk_drm_private *private = dev->dev_private;
+
+	return drm_gem_prime_import_dev(dev, dma_buf, private->dma_dev);
+}
+
 static struct drm_driver mtk_drm_driver = {
 	.driver_features = DRIVER_MODESET | DRIVER_GEM | DRIVER_PRIME |
 			   DRIVER_ATOMIC,
@@ -331,7 +372,7 @@ static struct drm_driver mtk_drm_driver = {
 	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,
 	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,
 	.gem_prime_export = drm_gem_prime_export,
-	.gem_prime_import = drm_gem_prime_import,
+	.gem_prime_import = mtk_drm_gem_prime_import,
 	.gem_prime_get_sg_table = mtk_gem_prime_get_sg_table,
 	.gem_prime_import_sg_table = mtk_gem_prime_import_sg_table,
 	.gem_prime_mmap = mtk_drm_gem_mmap_buf,
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.h b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
index 598ff3e70446..e03fea12ff59 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.h
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
@@ -51,6 +51,8 @@ struct mtk_drm_private {
 	} commit;
 
 	struct drm_atomic_state *suspend_state;
+
+	bool dma_parms_allocated;
 };
 
 extern struct platform_driver mtk_ddp_driver;
-- 
2.22.0.657.g960e92d24f-goog