linux-kernel - [PATCH] drm/rockchip: fix fbdev on non-IOMMU devices

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Message-Id: <20221020181248.2497065-1-john@metanate.com>
Date:   Thu, 20 Oct 2022 19:12:47 +0100
From:   John Keeping <john@...anate.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Johan Jonker <jbx6244@...il.com>, John Keeping <john@...anate.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/rockchip: fix fbdev on non-IOMMU devices

When switching to the generic fbdev infrastructure, it was missed that
framebuffers were created with the alloc_kmap parameter to
rockchip_gem_create_object() set to true.  The generic infrastructure
calls this via the .dumb_create() driver operation and thus creates a
buffer without an associated kmap.

alloc_kmap only makes a difference on devices without an IOMMU, but when
it is missing rockchip_gem_prime_vmap() fails and the framebuffer cannot
be used.

Detect the case where a buffer is being allocated for the framebuffer
and ensure a kernel mapping is created in this case.

Fixes: 24af7c34b290 ("drm/rockchip: use generic fbdev setup")
Reported-by: Johan Jonker <jbx6244@...il.com>
Cc: Thomas Zimmermann <tzimmermann@...e.de>
Signed-off-by: John Keeping <john@...anate.com>
---
 drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
index 614e97aaac80..da8a69953706 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_gem.c
@@ -364,9 +364,12 @@ rockchip_gem_create_with_handle(struct drm_file *file_priv,
 {
 	struct rockchip_gem_object *rk_obj;
 	struct drm_gem_object *obj;
+	bool is_framebuffer;
 	int ret;
 
-	rk_obj = rockchip_gem_create_object(drm, size, false);
+	is_framebuffer = drm->fb_helper && file_priv == drm->fb_helper->client.file;
+
+	rk_obj = rockchip_gem_create_object(drm, size, is_framebuffer);
 	if (IS_ERR(rk_obj))
 		return ERR_CAST(rk_obj);
 
-- 
2.38.1