Re: [PATCH v4 1/5] drm/rockchip: Add basic drm driver

On Mon, 22 Sep 2014 16:43:31 +0200
Arnd Bergmann [off-list ref] wrote:

On Monday 22 September 2014 18:48:54 Mark yao wrote:

quoted

diff --git a/drivers/gpu/drm/rockchip/Kconfig b/drivers/gpu/drm/rockchip/Kconfig
new file mode 100644
index 0000000..7146c80
--- /dev/null
+++ b/drivers/gpu/drm/rockchip/Kconfig

@@ -0,0 +1,19 @@
+config DRM_ROCKCHIP
+	tristate "DRM Support for Rockchip"
+	depends on DRM && ROCKCHIP_IOMMU
+	select ARM_DMA_USE_IOMMU
+	select IOMMU_API
+	select DRM_KMS_HELPER
+	select DRM_KMS_FB_HELPER
+	select DRM_PANEL
+	select FB_CFB_FILLRECT
+	select FB_CFB_COPYAREA
+	select FB_CFB_IMAGEBLIT
+	select VT_HW_CONSOLE_BINDING if FRAMEBUFFER_CONSOLE
+	select VIDEOMODE_HELPERS

Be careful with 'select', at least some of these should be 'depends on'.
In particular IOMMU_API and ARM_DMA_USE_IOMMU, but possibly others
as well. Just check how the symbols are used normally, if you get this
wrong, we can end up with incorrect dependencies or loops.

quoted

diff --git a/drivers/gpu/drm/rockchip/Makefile b/drivers/gpu/drm/rockchip/Makefile
new file mode 100644
index 0000000..6e6d468
--- /dev/null
+++ b/drivers/gpu/drm/rockchip/Makefile

@@ -0,0 +1,10 @@
+#
+# Makefile for the drm device driver.  This driver provides support for the
+# Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
+
+ccflags-y := -Iinclude/drm -Idrivers/gpu/drm/rockchip

The second one should not be required.

quoted

+static int rockchip_drm_load(struct drm_device *drm_dev, unsigned long flags)
+{
+	struct rockchip_drm_private *private;
+	struct dma_iommu_mapping *mapping;
+	struct device *dev = drm_dev->dev;
+	int ret;
+
+	private = devm_kzalloc(drm_dev->dev, sizeof(*private), GFP_KERNEL);
+	if (!private)
+		return -ENOMEM;
+
+	dev_set_drvdata(drm_dev->dev, dev);
+	drm_dev->dev_private = private;
+
+	drm_mode_config_init(drm_dev);
+
+	rockchip_drm_mode_config_init(drm_dev);
+
+	dev->dma_parms = devm_kzalloc(dev, sizeof(*dev->dma_parms),
+				      GFP_KERNEL);
+	if (!dev->dma_parms) {
+		ret = -ENOMEM;
+		goto err_config_cleanup;
+	}
+
+	/* TODO(djkurtz): fetch the mapping start/size from somewhere */
+	mapping = arm_iommu_create_mapping(&platform_bus_type, 0x10000000,
+					   SZ_1G);
+	if (IS_ERR(mapping)) {
+		ret = PTR_ERR(mapping);
+		goto err_config_cleanup;
+	}
+
+	dma_set_coherent_mask(dev, DMA_BIT_MASK(32));

This is the default coherent mask. If you call this function, you
should normally check the return value, or call dma_set_mask first,
which you apparently don't do here, and in another place in this
patch.

By "This is the default mask" do you mean it shouldn't be called at
all ? Cause I ran into some trouble when not calling this in my
atmel-hlcdc driver.
Actually, in my case the platform device is created by the MFD core
which seems to let the coherent_dma_mask uninitialized.

Best Regards,

Boris


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com
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