[PATCH] drm/rockchip: fix fbdev crash when not use DRM_FBDEV_EMULATION

Mark yao
2016-08-03T08:56:20Z

On 2016?08?03? 16:46, Daniel Vetter wrote:
> On Wed, Aug 03, 2016 at 10:43:21AM +0200, Daniel Vetter wrote:
>> On Wed, Aug 03, 2016 at 04:13:45PM +0800, Mark Yao wrote:
>>> [ 1.162571] Unable to handle kernel NULL pointer dereference at virtual address 00000200
>>> [ 1.165656] Modules linked in:
>>> [ 1.165941] CPU: 5 PID: 143 Comm: kworker/5:2 Not tainted 4.4.15 #237
>>> [ 1.166506] Hardware name: Rockchip RK3399 Evaluation Board v1 (Android) (DT)
>>> [ 1.167153] Workqueue: events output_poll_execute
>>> [ 1.168231] PC is at mutex_lock+0x14/0x44
>>> [ 1.168586] LR is at drm_fb_helper_hotplug_event+0x28/0xcc
>>> [ 1.172192] [<ffffff8008982110>] mutex_lock+0x14/0x44
>>> [ 1.172196] [<ffffff80084025a4>] drm_fb_helper_hotplug_event+0x28/0xcc
>>> [ 1.172201] [<ffffff8008427ae4>] rockchip_drm_output_poll_changed+0x14/0x1c
>>> [ 1.172204] [<ffffff80083f7c4c>] drm_kms_helper_hotplug_event+0x28/0x34
>>> [ 1.172207] [<ffffff80083f7ddc>] output_poll_execute+0x150/0x198
>>> [ 1.172212] [<ffffff80080b0ea8>] process_one_work+0x218/0x3dc
>>> [ 1.172215] [<ffffff80080b1578>] worker_thread+0x24c/0x374
>>> [ 1.172217] [<ffffff80080b5bcc>] kthread+0xdc/0xe4
>>> [ 1.172222] [<ffffff8008084cd0>] ret_from_fork+0x10/0x40
>>>
>>> Signed-off-by: Mark Yao <mark.yao@rock-chips.com>
>> Erhm, how exactly did you manage to blow up in there? Without fbdev
>> support enable drm_fb_helper_hotplug_event() does nothing at all.
>>
>> The fbdev helper is designed such that you _don't_ have to check for NULL
>> everywhere in the driver, that would be pretty bad code.
> And indeed this issue seems preexisting, and was already attempt to fix in
>
> commit 765c35bbd267e93eabe15a94534688ddaa0b9dc7
> Author: Heiko St?bner <heiko@sntech.de>
> Date: Tue Jun 2 16:41:45 2015 +0200
>
> drm/rockchip: only call drm_fb_helper_hotplug_event if fb_helper present
>
> except that patch is complete nonsense - the added check is always true.
> Oh and it's missing your s-o-b, which is not good at all.
>
> The proper fix is to make delayed fbdev loading work correctly, Thierry
> has patches for that on the mailing list. Not add even more hacks like the
> above (and then slap a misleading subject onto your patch).
> -Daniel

Hmmm, there is a mistake on Heiko's patch:

struct drm_fb_helper *fb_helper = &private->fbdev_helper;

- drm_fb_helper_hotplug_event(fb_helper);
+ if (fb_helper)
+ drm_fb_helper_hotplug_event(fb_helper);

But the fb_helper would never be NULL, because the private->fbdev_helper
is not a pointer.

So the first step is making private->fbdev_helper to a pointer, that's
what I do on this patch.

>> -Daniel
>>
>>> ---
>>> drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 13 ++++++++++---
>>> drivers/gpu/drm/rockchip/rockchip_drm_drv.h | 8 ++++++--
>>> drivers/gpu/drm/rockchip/rockchip_drm_fb.c | 6 +++---
>>> drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c | 26 +++++++++++++++++---------
>>> 4 files changed, 36 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
>>> index a822d49..1a4dad6 100644
>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
>>> @@ -261,7 +261,10 @@ static void rockchip_drm_lastclose(struct drm_device *dev)
>>> {
>>> struct rockchip_drm_private *priv = dev->dev_private;
>>>
>>> - drm_fb_helper_restore_fbdev_mode_unlocked(&priv->fbdev_helper);
>>> + if (!priv->fbdev)
>>> + return;
>>> +
>>> + drm_fb_helper_restore_fbdev_mode_unlocked(&priv->fbdev->fbdev_helper);
>>> }
>>>
>>> static const struct file_operations rockchip_drm_driver_fops = {
>>> @@ -310,8 +313,10 @@ void rockchip_drm_fb_suspend(struct drm_device *drm)
>>> {
>>> struct rockchip_drm_private *priv = drm->dev_private;
>>>
>>> + if (!priv->fbdev)
>>> + return;
>>> console_lock();
>>> - drm_fb_helper_set_suspend(&priv->fbdev_helper, 1);
>>> + drm_fb_helper_set_suspend(&priv->fbdev->fbdev_helper, 1);
>>> console_unlock();
>>> }
>>>
>>> @@ -319,8 +324,10 @@ void rockchip_drm_fb_resume(struct drm_device *drm)
>>> {
>>> struct rockchip_drm_private *priv = drm->dev_private;
>>>
>>> + if (!priv->fbdev)
>>> + return;
>>> console_lock();
>>> - drm_fb_helper_set_suspend(&priv->fbdev_helper, 0);
>>> + drm_fb_helper_set_suspend(&priv->fbdev->fbdev_helper, 0);
>>> console_unlock();
>>> }
>>>
>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
>>> index ea39329..c054fc2 100644
>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.h
>>> @@ -50,6 +50,11 @@ struct rockchip_crtc_state {
>>> #define to_rockchip_crtc_state(s) \
>>> container_of(s, struct rockchip_crtc_state, base)
>>>
>>> +struct rockchip_drm_fbdev {
>>> + struct drm_fb_helper fbdev_helper;
>>> + struct drm_gem_object *fbdev_bo;
>>> +};
>>> +
>>> /*
>>> * Rockchip drm private structure.
>>> *
>>> @@ -57,8 +62,7 @@ struct rockchip_crtc_state {
>>> * @num_pipe: number of pipes for this device.
>>> */
>>> struct rockchip_drm_private {
>>> - struct drm_fb_helper fbdev_helper;
>>> - struct drm_gem_object *fbdev_bo;
>>> + struct rockchip_drm_fbdev *fbdev;
>>> const struct rockchip_crtc_funcs *crtc_funcs[ROCKCHIP_MAX_CRTC];
>>> struct drm_atomic_state *state;
>>> };
>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
>>> index 55c5273..fef6f8d 100644
>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fb.c
>>> @@ -156,10 +156,10 @@ err_gem_object_unreference:
>>> static void rockchip_drm_output_poll_changed(struct drm_device *dev)
>>> {
>>> struct rockchip_drm_private *private = dev->dev_private;
>>> - struct drm_fb_helper *fb_helper = &private->fbdev_helper;
>>> + struct rockchip_drm_fbdev *fbdev = private->fbdev;
>>>
>>> - if (fb_helper)
>>> - drm_fb_helper_hotplug_event(fb_helper);
>>> + if (fbdev)
>>> + drm_fb_helper_hotplug_event(&fbdev->fbdev_helper);
>>> }
>>>
>>> static void rockchip_crtc_wait_for_update(struct drm_crtc *crtc)
>>> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c b/drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c
>>> index 207e01d..cc5781a 100644
>>> --- a/drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c
>>> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_fbdev.c
>>> @@ -22,16 +22,16 @@
>>> #include "rockchip_drm_fb.h"
>>>
>>> #define PREFERRED_BPP 32
>>> -#define to_drm_private(x) \
>>> - container_of(x, struct rockchip_drm_private, fbdev_helper)
>>> +#define to_rockchip_fbdev(x) \
>>> + container_of(x, struct rockchip_drm_fbdev, fbdev_helper)
>>>
>>> static int rockchip_fbdev_mmap(struct fb_info *info,
>>> struct vm_area_struct *vma)
>>> {
>>> struct drm_fb_helper *helper = info->par;
>>> - struct rockchip_drm_private *private = to_drm_private(helper);
>>> + struct rockchip_drm_fbdev *fbdev = to_rockchip_fbdev(helper);
>>>
>>> - return rockchip_gem_mmap_buf(private->fbdev_bo, vma);
>>> + return rockchip_gem_mmap_buf(fbdev->fbdev_bo, vma);
>>> }
>>>
>>> static struct fb_ops rockchip_drm_fbdev_ops = {
>>> @@ -50,7 +50,7 @@ static struct fb_ops rockchip_drm_fbdev_ops = {
>>> static int rockchip_drm_fbdev_create(struct drm_fb_helper *helper,
>>> struct drm_fb_helper_surface_size *sizes)
>>> {
>>> - struct rockchip_drm_private *private = to_drm_private(helper);
>>> + struct rockchip_drm_fbdev *fbdev = to_rockchip_fbdev(helper);
>>> struct drm_mode_fb_cmd2 mode_cmd = { 0 };
>>> struct drm_device *dev = helper->dev;
>>> struct rockchip_gem_object *rk_obj;
>>> @@ -75,7 +75,7 @@ static int rockchip_drm_fbdev_create(struct drm_fb_helper *helper,
>>> if (IS_ERR(rk_obj))
>>> return -ENOMEM;
>>>
>>> - private->fbdev_bo = &rk_obj->base;
>>> + fbdev->fbdev_bo = &rk_obj->base;
>>>
>>> fbi = drm_fb_helper_alloc_fbi(helper);
>>> if (IS_ERR(fbi)) {
>>> @@ -85,7 +85,7 @@ static int rockchip_drm_fbdev_create(struct drm_fb_helper *helper,
>>> }
>>>
>>> helper->fb = rockchip_drm_framebuffer_init(dev, &mode_cmd,
>>> - private->fbdev_bo);
>>> + fbdev->fbdev_bo);
>>> if (IS_ERR(helper->fb)) {
>>> dev_err(dev->dev, "Failed to allocate DRM framebuffer.\n");
>>> ret = PTR_ERR(helper->fb);
>>> @@ -130,6 +130,7 @@ static const struct drm_fb_helper_funcs rockchip_drm_fb_helper_funcs = {
>>> int rockchip_drm_fbdev_init(struct drm_device *dev)
>>> {
>>> struct rockchip_drm_private *private = dev->dev_private;
>>> + struct rockchip_drm_fbdev *fbdev;
>>> struct drm_fb_helper *helper;
>>> unsigned int num_crtc;
>>> int ret;
>>> @@ -139,7 +140,12 @@ int rockchip_drm_fbdev_init(struct drm_device *dev)
>>>
>>> num_crtc = dev->mode_config.num_crtc;
>>>
>>> - helper = &private->fbdev_helper;
>>> + fbdev = devm_kzalloc(dev->dev, sizeof(*fbdev), GFP_KERNEL);
>>> + if (!fbdev)
>>> + return -ENOMEM;
>>> +
>>> + private->fbdev = fbdev;
>>> + helper = &fbdev->fbdev_helper;
>>>
>>> drm_fb_helper_prepare(dev, helper, &rockchip_drm_fb_helper_funcs);
>>>
>>> @@ -175,7 +181,9 @@ void rockchip_drm_fbdev_fini(struct drm_device *dev)
>>> struct rockchip_drm_private *private = dev->dev_private;
>>> struct drm_fb_helper *helper;
>>>
>>> - helper = &private->fbdev_helper;
>>> + if (!private || private->fbdev)
>>> + return;
>>> + helper = &private->fbdev->fbdev_helper;
>>>
>>> drm_fb_helper_unregister_fbi(helper);
>>> drm_fb_helper_release_fbi(helper);
>>> --
>>> 1.9.1
>>>
>>>
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel at lists.freedesktop.org
>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> http://blog.ffwll.ch

--
?ark Yao