[PATCH v3 9/9] drm/simpledrm: Acquire memory aperture for framebuffer

From: Thomas Zimmermann <tzimmermann@suse.de>
To: daniel@ffwll.ch, airlied@linux.ie,
	maarten.lankhorst@linux.intel.com, mripard@kernel.org,
	kraxel@redhat.com, corbet@lwn.net, lgirdwood@gmail.com,
	broonie@kernel.org, sam@ravnborg.org, robh@kernel.org,
	emil.l.velikov@gmail.com, geert+renesas@glider.be,
	hdegoede@redhat.com, bluescreen_avenger@verizon.net,
	gregkh@linuxfoundation.org
Cc: dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	Thomas Zimmermann <tzimmermann@suse.de>
Subject: [PATCH v3 9/9] drm/simpledrm: Acquire memory aperture for framebuffer
Date: Thu, 15 Apr 2021 10:53:26 +0200	[thread overview]
Message-ID: <20210415085326.8824-10-tzimmermann@suse.de> (raw)
In-Reply-To: <20210415085326.8824-1-tzimmermann@suse.de>

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

The original generic platform device from the simple-framebuffer boot
code will be unregistered. The native driver will use whatever native
hardware device it received.

v3:
	* use platform_device_unregister() and handle detachment
	  like hot-unplug event (Daniel)
v2:
	* adapt to aperture changes
	* use drm_dev_unplug() and drm_dev_enter/exit()
	* don't split error string

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Tested-by: nerdopolis <bluescreen_avenger@verizon.net>
---
 drivers/gpu/drm/tiny/simpledrm.c | 49 +++++++++++++++++++++++++++++++-
 1 file changed, 48 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tiny/simpledrm.c b/drivers/gpu/drm/tiny/simpledrm.c
index 9d522473cd7c..14473e1bccab 100644
--- a/drivers/gpu/drm/tiny/simpledrm.c
+++ b/drivers/gpu/drm/tiny/simpledrm.c
@@ -6,6 +6,7 @@
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
 
+#include <drm/drm_aperture.h>
 #include <drm/drm_atomic_state_helper.h>
 #include <drm/drm_connector.h>
 #include <drm/drm_damage_helper.h>
@@ -515,16 +516,49 @@ static int simpledrm_device_init_fb(struct simpledrm_device *sdev)
  * Memory management
  */
 
+static void simpledrm_aperture_detach(struct drm_device *dev, resource_size_t base,
+				      resource_size_t size)
+{
+	struct simpledrm_device *sdev = simpledrm_device_of_dev(dev);
+	struct platform_device *pdev = sdev->pdev;
+
+	/*
+	 * Remove the device from the bus itself. This is the right thing to
+	 * do for the generic DRM drivers, such as EFI, VESA or VGA. When the
+	 * new driver takes over the hardware, the generic device's state will
+	 * be lost.
+	 *
+	 * If the aperture helpers need to handle native drivers, this call
+	 * would only have to unplug the DRM device, so that the hardware device
+	 * stays around after detachment.
+	 */
+	platform_device_unregister(pdev);
+}
+
+static const struct drm_aperture_funcs simpledrm_aperture_funcs = {
+	.detach = simpledrm_aperture_detach,
+};
+
 static int simpledrm_device_init_mm(struct simpledrm_device *sdev)
 {
+	struct drm_device *dev = &sdev->dev;
 	struct platform_device *pdev = sdev->pdev;
 	struct resource *mem;
 	void __iomem *screen_base;
+	int ret;
 
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!mem)
 		return -EINVAL;
 
+	ret = devm_aperture_acquire(dev, mem->start, resource_size(mem),
+				    &simpledrm_aperture_funcs);
+	if (ret) {
+		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)
@@ -625,12 +659,18 @@ simpledrm_simple_display_pipe_enable(struct drm_simple_display_pipe *pipe,
 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
 	struct drm_framebuffer *fb = plane_state->fb;
 	void *vmap = shadow_plane_state->map[0].vaddr; /* TODO: Use mapping abstraction properly */
+	struct drm_device *dev = &sdev->dev;
+	int idx;
 
 	if (!fb)
 		return;
 
+	if (!drm_dev_enter(dev, &idx))
+		return;
+
 	drm_fb_blit_dstclip(sdev->screen_base, sdev->pitch,
 			    sdev->format->format, vmap, fb);
+	drm_dev_exit(idx);
 }
 
 static void
@@ -658,7 +698,9 @@ simpledrm_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
 	struct drm_shadow_plane_state *shadow_plane_state = to_drm_shadow_plane_state(plane_state);
 	void *vmap = shadow_plane_state->map[0].vaddr; /* TODO: Use mapping abstraction properly */
 	struct drm_framebuffer *fb = plane_state->fb;
+	struct drm_device *dev = &sdev->dev;
 	struct drm_rect clip;
+	int idx;
 
 	if (!fb)
 		return;
@@ -666,8 +708,13 @@ simpledrm_simple_display_pipe_update(struct drm_simple_display_pipe *pipe,
 	if (!drm_atomic_helper_damage_merged(old_plane_state, plane_state, &clip))
 		return;
 
+	if (!drm_dev_enter(dev, &idx))
+		return;
+
 	drm_fb_blit_rect_dstclip(sdev->screen_base, sdev->pitch,
 				 sdev->format->format, vmap, fb, &clip);
+
+	drm_dev_exit(idx);
 }
 
 static const struct drm_simple_display_pipe_funcs
@@ -847,7 +894,7 @@ static int simpledrm_remove(struct platform_device *pdev)
 	struct simpledrm_device *sdev = platform_get_drvdata(pdev);
 	struct drm_device *dev = &sdev->dev;
 
-	drm_dev_unregister(dev);
+	drm_dev_unplug(dev);
 
 	return 0;
 }
-- 
2.31.1

