[PATCH 9/9] drm/simplekms: Acquire memory aperture for framebuffer

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We register the simplekms device with the DRM platform helpers. A
native driver for the graphics hardware will kickout the simplekms
driver before taking over the device.

Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
---
 drivers/gpu/drm/tiny/Kconfig     |  1 +
 drivers/gpu/drm/tiny/simplekms.c | 94 +++++++++++++++++++++++++++++++-
 2 files changed, 92 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/tiny/Kconfig b/drivers/gpu/drm/tiny/Kconfig
index 50dbde8bdcb2..a47ed337a7fe 100644
--- a/drivers/gpu/drm/tiny/Kconfig
+++ b/drivers/gpu/drm/tiny/Kconfig
@@ -33,6 +33,7 @@ config DRM_SIMPLEKMS
 	depends on DRM
 	select DRM_GEM_SHMEM_HELPER
 	select DRM_KMS_HELPER
+	select DRM_PLATFORM_HELPER
 	help
 	  DRM driver for simple platform-provided framebuffers.
 
diff --git a/drivers/gpu/drm/tiny/simplekms.c b/drivers/gpu/drm/tiny/simplekms.c
index ae5d3cbadbe8..a903a4e0100a 100644
--- a/drivers/gpu/drm/tiny/simplekms.c
+++ b/drivers/gpu/drm/tiny/simplekms.c
@@ -5,6 +5,7 @@
 #include <linux/platform_data/simplefb.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
+#include <linux/spinlock.h>
 
 #include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_connector.h>
@@ -17,6 +18,7 @@
 #include <drm/drm_gem_shmem_helper.h>
 #include <drm/drm_managed.h>
 #include <drm/drm_modeset_helper_vtables.h>
+#include <drm/drm_platform.h>
 #include <drm/drm_probe_helper.h>
 #include <drm/drm_simple_kms_helper.h>
 
@@ -36,6 +38,12 @@
 #define SIMPLEKMS_MODE(hd, vd)	\
 	DRM_SIMPLE_MODE(hd, vd, RES_MM(hd), RES_MM(vd))
 
+/*
+ * Protects the platform device's drvdata against
+ * concurrent manipulation.
+ */
+static DEFINE_SPINLOCK(simplekms_drvdata_lock);
+
 /*
  * Helpers for simplefb
  */
@@ -211,6 +219,7 @@ struct simplekms_device {
 	unsigned int pitch;
 
 	/* memory management */
+	struct drm_aperture *aperture;
 	struct resource *mem;
 	void __iomem *screen_base;
 
@@ -224,6 +233,8 @@ static struct simplekms_device *simplekms_device_of_dev(struct drm_device *dev)
 	return container_of(dev, struct simplekms_device, dev);
 }
 
+static void simplekms_device_cleanup(struct simplekms_device *sdev);
+
 /*
  * Hardware
  */
@@ -514,22 +525,72 @@ static int simplekms_device_init_fb(struct simplekms_device *sdev)
  * Memory management
  */
 
+static void simplekms_aperture_kickout(struct drm_aperture *ap)
+{
+	struct drm_device *dev = ap->dev;
+	struct simplekms_device *sdev = simplekms_device_of_dev(dev);
+	struct platform_device *pdev = sdev->pdev;
+
+	if (WARN_ON(!sdev->aperture))
+		return; /* BUG: driver already got kicked out */
+
+	drm_dev_unregister(dev);
+
+	sdev->aperture = NULL; /* memory is released by platform helpers */
+
+	spin_lock(&simplekms_drvdata_lock);
+	sdev = platform_get_drvdata(pdev);
+	platform_set_drvdata(pdev, NULL); /* required; see simplekms_remove() */
+	spin_unlock(&simplekms_drvdata_lock);
+
+	/*
+	 * Return if a concurrent simplekms_remove() cleans up the
+	 * device. See simplekms_remove().
+	 */
+	if (!sdev)
+		return;
+
+	/*
+	 * After the aperture has been released, there's no reason
+	 * to keep the DRM device around.
+	 */
+	simplekms_device_cleanup(sdev);
+}
+
+static const struct drm_aperture_funcs simplekms_aperture_funcs = {
+	.kickout = simplekms_aperture_kickout,
+};
+
 static int simplekms_device_init_mm(struct simplekms_device *sdev)
 {
+	struct drm_device *dev = &sdev->dev;
 	struct platform_device *pdev = sdev->pdev;
 	struct resource *mem;
+	struct drm_aperture *ap;
 	void __iomem *screen_base;
+	int ret;
 
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!mem)
 		return -EINVAL;
 
+	ap = drmm_aperture_acquire(dev, mem->start, resource_size(mem),
+				   &simplekms_aperture_funcs);
+	if (IS_ERR(ap)) {
+		ret = PTR_ERR(ap);
+		drm_err(dev,
+			"could not acquire memory range [0x%llx:0x%llx]: "
+			"error %d\n", mem->start, mem->end, ret);
+		return ret;
+	}
+
 	screen_base = devm_ioremap_wc(&pdev->dev, mem->start,
 				      resource_size(mem));
 	if (!screen_base)
 		return -ENOMEM;
 
 	sdev->mem = mem;
+	sdev->aperture = ap;
 	sdev->screen_base = screen_base;
 
 	return 0;
@@ -625,6 +686,9 @@ simplekms_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
 	struct drm_framebuffer *fb = state->fb;
 	void *vmap;
 
+	if (!sdev->aperture)
+		return;
+
 	vmap = drm_gem_shmem_vmap(fb->obj[0]);
 	if (!vmap)
 		return;
@@ -645,6 +709,9 @@ simplekms_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
 	struct drm_rect clip;
 	void *vmap;
 
+	if (!sdev->aperture)
+		return;
+
 	if (!drm_atomic_helper_damage_merged(old_plane_state, state, &clip))
 		return;
 
@@ -716,11 +783,12 @@ static int simplekms_device_init_modeset(struct simplekms_device *sdev)
  * Init / Cleanup
  */
 
-static void simplekms_device_cleanup(struct simplekms_device* sdev)
+static void simplekms_device_cleanup(struct simplekms_device *sdev)
 {
 	struct drm_device *dev = &sdev->dev;
 
-	drm_dev_unregister(dev);
+	if (dev->registered)
+		drm_dev_unregister(dev);
 }
 
 static struct simplekms_device *
@@ -797,7 +865,27 @@ static int simplekms_probe(struct platform_device *pdev)
 
 static int simplekms_remove(struct platform_device *pdev)
 {
-	struct simplekms_device *sdev = platform_get_drvdata(pdev);
+	struct simplekms_device *sdev;
+
+	spin_lock(&simplekms_drvdata_lock);
+	sdev = platform_get_drvdata(pdev);
+	platform_set_drvdata(pdev, NULL);
+	spin_unlock(&simplekms_drvdata_lock);
+
+	/*
+	 * The platform driver shares its reference to dev with the
+	 * platform helpers for apertures. That reference is either
+	 * released here when unloading the driver; or it's released
+	 * when the driver gets kicked out by another driver. In the
+	 * latter case, the aperture release routine clears the data
+	 * field of the platform device.
+	 *
+	 * Therefore, sdev being NULL is a valid state if the driver
+	 * has been kicked out by another DRM driver. In this case,
+	 * it's all been cleaned up and we can return immediately.
+	 */
+	if (!sdev)
+		return 0;
 
 	simplekms_device_cleanup(sdev);
 
-- 
2.27.0

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