linux-kernel - [PATCH v2] drm/rockchip: remove existing generic drivers to take over the device

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Date:   Sun, 16 May 2021 09:48:33 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Robinson <pbrobinson@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Heiko Stübner <heiko@...ech.de>,
        Sandy Huang <hjc@...k-chips.com>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org
Subject: [PATCH v2] drm/rockchip: remove existing generic drivers to take over the device

There are drivers that register framebuffer devices very early in the boot
process and make use of the existing framebuffer as setup by the firmware.

If one of those drivers has registered a fbdev, then the fallback fbdev of
the DRM driver won't be bound to the framebuffer console. To avoid that,
remove any existing generic driver and take over the graphics device.

By doing that, the fb mapped to the console is switched correctly from the
early fbdev to the one registered by the rockchip DRM driver:

    [   40.752420] fb0: switching to rockchip-drm-fb from EFI VGA

Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
---

Changes in v2:
- Move drm_aperture_remove_framebuffers() call to .bind callback (tzimmermann).
- Adapt subject line, commit message, etc accordingly.

 drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
index 212bd87c0c4..b730b8d5d94 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
@@ -16,6 +16,7 @@
 #include <linux/console.h>
 #include <linux/iommu.h>
 
+#include <drm/drm_aperture.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_fb_helper.h>
 #include <drm/drm_gem_cma_helper.h>
@@ -114,6 +115,15 @@ static int rockchip_drm_bind(struct device *dev)
 	struct rockchip_drm_private *private;
 	int ret;
 
+	/* Remove existing drivers that may own the framebuffer memory. */
+	ret = drm_aperture_remove_framebuffers(false, "rockchip-drm-fb");
+	if (ret) {
+		DRM_DEV_ERROR(dev,
+			      "Failed to remove existing framebuffers - %d.\n",
+			      ret);
+		return ret;
+	}
+
 	drm_dev = drm_dev_alloc(&rockchip_drm_driver, dev);
 	if (IS_ERR(drm_dev))
 		return PTR_ERR(drm_dev);
-- 
2.31.1