Re: [PATCH] Revert "drm/mgag200: Add vblank support"

[Jocelyn Falempe <jfalempe@xxxxxxxxxx>]

On 15/10/2024 08:37, Thomas Zimmermann wrote:
> This reverts commit 6c9e14ee9f519ee605a3694fbfa4711284781d22.
> This reverts commit d5070c9b29440c270b534bbacd636b8fa558e82b.
> This reverts commit 89c6ea2006e2d39b125848fb0195c08fa0b354be.
>
> The VLINE interrupt doesn't work correctly on G200SE-A (at least). We
> have also seen missing interrupts on G200ER. So revert vblank support.
> Fixes frozen displays and warnings about missed vblanks.
>
> [   33.818362] [CRTC:34:crtc-0] vblank wait timed out
>
>  From the vblank code, the driver only keeps the register constants and
> the line that disables all interrupts in mgag200_device_init(). Both
> is still useful without vblank handling.

Thanks, it looks good to me.
As there are broken hardware, that's the only solution left.

Reviewed-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>


> Reported-by: Tony Luck <tony.luck@xxxxxxxxx>
> Closes: https://lore.kernel.org/dri-devel/Zvx6lSi7oq5xvTZb@xxxxxxxxxxxxxxxxxxxxxxxxx/raw
> Tested-by: Tony Luck <tony.luck@xxxxxxxxx>
> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> ---
>   drivers/gpu/drm/mgag200/mgag200_drv.c     | 38 -----------
>   drivers/gpu/drm/mgag200/mgag200_drv.h     | 14 +----
>   drivers/gpu/drm/mgag200/mgag200_g200.c    |  5 --
>   drivers/gpu/drm/mgag200/mgag200_g200eh.c  |  5 --
>   drivers/gpu/drm/mgag200/mgag200_g200eh3.c |  5 --
>   drivers/gpu/drm/mgag200/mgag200_g200er.c  | 10 +--
>   drivers/gpu/drm/mgag200/mgag200_g200ev.c  | 10 +--
>   drivers/gpu/drm/mgag200/mgag200_g200ew3.c |  5 --
>   drivers/gpu/drm/mgag200/mgag200_g200se.c  | 10 +--
>   drivers/gpu/drm/mgag200/mgag200_g200wb.c  |  5 --
>   drivers/gpu/drm/mgag200/mgag200_mode.c    | 77 +----------------------
>   11 files changed, 6 insertions(+), 178 deletions(-)
>
> diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c b/drivers/gpu/drm/mgag200/mgag200_drv.c
> index 42fabe817e21..97fd7eb765b4 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_drv.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_drv.c
> @@ -20,7 +20,6 @@
>   #include <drm/drm_managed.h>
>   #include <drm/drm_module.h>
>   #include <drm/drm_pciids.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_drv.h"
>   
> @@ -87,34 +86,6 @@ resource_size_t mgag200_probe_vram(void __iomem *mem, resource_size_t size)
>   	return offset - 65536;
>   }
>   
> -static irqreturn_t mgag200_irq_handler(int irq, void *arg)
> -{
> -	struct drm_device *dev = arg;
> -	struct mga_device *mdev = to_mga_device(dev);
> -	struct drm_crtc *crtc;
> -	u32 status, ien;
> -
> -	status = RREG32(MGAREG_STATUS);
> -
> -	if (status & MGAREG_STATUS_VLINEPEN) {
> -		ien = RREG32(MGAREG_IEN);
> -		if (!(ien & MGAREG_IEN_VLINEIEN))
> -			goto out;
> -
> -		crtc = drm_crtc_from_index(dev, 0);
> -		if (WARN_ON_ONCE(!crtc))
> -			goto out;
> -		drm_crtc_handle_vblank(crtc);
> -
> -		WREG32(MGAREG_ICLEAR, MGAREG_ICLEAR_VLINEICLR);
> -
> -		return IRQ_HANDLED;
> -	}
> -
> -out:
> -	return IRQ_NONE;
> -}
> -
>   /*
>    * DRM driver
>    */
> @@ -199,7 +170,6 @@ int mgag200_device_init(struct mga_device *mdev,
>   			const struct mgag200_device_funcs *funcs)
>   {
>   	struct drm_device *dev = &mdev->base;
> -	struct pci_dev *pdev = to_pci_dev(dev->dev);
>   	u8 crtcext3, misc;
>   	int ret;
>   
> @@ -226,14 +196,6 @@ int mgag200_device_init(struct mga_device *mdev,
>   	mutex_unlock(&mdev->rmmio_lock);
>   
>   	WREG32(MGAREG_IEN, 0);
> -	WREG32(MGAREG_ICLEAR, MGAREG_ICLEAR_VLINEICLR);
> -
> -	ret = devm_request_irq(&pdev->dev, pdev->irq, mgag200_irq_handler, IRQF_SHARED,
> -			       dev->driver->name, dev);
> -	if (ret) {
> -		drm_err(dev, "Failed to acquire interrupt, error %d\n", ret);
> -		return ret;
> -	}
>   
>   	return 0;
>   }
> diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.h b/drivers/gpu/drm/mgag200/mgag200_drv.h
> index 4760ba92871b..988967eafbf2 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_drv.h
> +++ b/drivers/gpu/drm/mgag200/mgag200_drv.h
> @@ -391,24 +391,17 @@ int mgag200_crtc_helper_atomic_check(struct drm_crtc *crtc, struct drm_atomic_st
>   void mgag200_crtc_helper_atomic_flush(struct drm_crtc *crtc, struct drm_atomic_state *old_state);
>   void mgag200_crtc_helper_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_state *old_state);
>   void mgag200_crtc_helper_atomic_disable(struct drm_crtc *crtc, struct drm_atomic_state *old_state);
> -bool mgag200_crtc_helper_get_scanout_position(struct drm_crtc *crtc, bool in_vblank_irq,
> -					      int *vpos, int *hpos,
> -					      ktime_t *stime, ktime_t *etime,
> -					      const struct drm_display_mode *mode);
>   
>   #define MGAG200_CRTC_HELPER_FUNCS \
>   	.mode_valid = mgag200_crtc_helper_mode_valid, \
>   	.atomic_check = mgag200_crtc_helper_atomic_check, \
>   	.atomic_flush = mgag200_crtc_helper_atomic_flush, \
>   	.atomic_enable = mgag200_crtc_helper_atomic_enable, \
> -	.atomic_disable = mgag200_crtc_helper_atomic_disable, \
> -	.get_scanout_position = mgag200_crtc_helper_get_scanout_position
> +	.atomic_disable = mgag200_crtc_helper_atomic_disable
>   
>   void mgag200_crtc_reset(struct drm_crtc *crtc);
>   struct drm_crtc_state *mgag200_crtc_atomic_duplicate_state(struct drm_crtc *crtc);
>   void mgag200_crtc_atomic_destroy_state(struct drm_crtc *crtc, struct drm_crtc_state *crtc_state);
> -int mgag200_crtc_enable_vblank(struct drm_crtc *crtc);
> -void mgag200_crtc_disable_vblank(struct drm_crtc *crtc);
>   
>   #define MGAG200_CRTC_FUNCS \
>   	.reset = mgag200_crtc_reset, \
> @@ -416,10 +409,7 @@ void mgag200_crtc_disable_vblank(struct drm_crtc *crtc);
>   	.set_config = drm_atomic_helper_set_config, \
>   	.page_flip = drm_atomic_helper_page_flip, \
>   	.atomic_duplicate_state = mgag200_crtc_atomic_duplicate_state, \
> -	.atomic_destroy_state = mgag200_crtc_atomic_destroy_state, \
> -	.enable_vblank = mgag200_crtc_enable_vblank, \
> -	.disable_vblank = mgag200_crtc_disable_vblank, \
> -	.get_vblank_timestamp = drm_crtc_vblank_helper_get_vblank_timestamp
> +	.atomic_destroy_state = mgag200_crtc_atomic_destroy_state
>   
>   void mgag200_set_mode_regs(struct mga_device *mdev, const struct drm_display_mode *mode,
>   			   bool set_vidrst);
> diff --git a/drivers/gpu/drm/mgag200/mgag200_g200.c b/drivers/gpu/drm/mgag200/mgag200_g200.c
> index 77ce8d36cef0..f874e2949840 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_g200.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_g200.c
> @@ -8,7 +8,6 @@
>   #include <drm/drm_drv.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_drv.h"
>   
> @@ -404,9 +403,5 @@ struct mga_device *mgag200_g200_device_create(struct pci_dev *pdev, const struct
>   	drm_mode_config_reset(dev);
>   	drm_kms_helper_poll_init(dev);
>   
> -	ret = drm_vblank_init(dev, 1);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
>   	return mdev;
>   }
> diff --git a/drivers/gpu/drm/mgag200/mgag200_g200eh.c b/drivers/gpu/drm/mgag200/mgag200_g200eh.c
> index 09ced65c1d2f..e2305f8e00f8 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_g200eh.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_g200eh.c
> @@ -8,7 +8,6 @@
>   #include <drm/drm_drv.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_drv.h"
>   
> @@ -276,9 +275,5 @@ struct mga_device *mgag200_g200eh_device_create(struct pci_dev *pdev, const stru
>   	drm_mode_config_reset(dev);
>   	drm_kms_helper_poll_init(dev);
>   
> -	ret = drm_vblank_init(dev, 1);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
>   	return mdev;
>   }
> diff --git a/drivers/gpu/drm/mgag200/mgag200_g200eh3.c b/drivers/gpu/drm/mgag200/mgag200_g200eh3.c
> index 5daa469137bd..11ae76eb081d 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_g200eh3.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_g200eh3.c
> @@ -7,7 +7,6 @@
>   #include <drm/drm_drv.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_drv.h"
>   
> @@ -181,9 +180,5 @@ struct mga_device *mgag200_g200eh3_device_create(struct pci_dev *pdev,
>   	drm_mode_config_reset(dev);
>   	drm_kms_helper_poll_init(dev);
>   
> -	ret = drm_vblank_init(dev, 1);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
>   	return mdev;
>   }
> diff --git a/drivers/gpu/drm/mgag200/mgag200_g200er.c b/drivers/gpu/drm/mgag200/mgag200_g200er.c
> index 09cfffafe130..c20ed0ab50ec 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_g200er.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_g200er.c
> @@ -8,7 +8,6 @@
>   #include <drm/drm_drv.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_drv.h"
>   
> @@ -206,8 +205,6 @@ static void mgag200_g200er_crtc_helper_atomic_enable(struct drm_crtc *crtc,
>   		mgag200_crtc_set_gamma_linear(mdev, format);
>   
>   	mgag200_enable_display(mdev);
> -
> -	drm_crtc_vblank_on(crtc);
>   }
>   
>   static const struct drm_crtc_helper_funcs mgag200_g200er_crtc_helper_funcs = {
> @@ -215,8 +212,7 @@ static const struct drm_crtc_helper_funcs mgag200_g200er_crtc_helper_funcs = {
>   	.atomic_check = mgag200_crtc_helper_atomic_check,
>   	.atomic_flush = mgag200_crtc_helper_atomic_flush,
>   	.atomic_enable = mgag200_g200er_crtc_helper_atomic_enable,
> -	.atomic_disable = mgag200_crtc_helper_atomic_disable,
> -	.get_scanout_position = mgag200_crtc_helper_get_scanout_position,
> +	.atomic_disable = mgag200_crtc_helper_atomic_disable
>   };
>   
>   static const struct drm_crtc_funcs mgag200_g200er_crtc_funcs = {
> @@ -312,9 +308,5 @@ struct mga_device *mgag200_g200er_device_create(struct pci_dev *pdev, const stru
>   	drm_mode_config_reset(dev);
>   	drm_kms_helper_poll_init(dev);
>   
> -	ret = drm_vblank_init(dev, 1);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
>   	return mdev;
>   }
> diff --git a/drivers/gpu/drm/mgag200/mgag200_g200ev.c b/drivers/gpu/drm/mgag200/mgag200_g200ev.c
> index 3d48baa91d8b..78be964eb97c 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_g200ev.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_g200ev.c
> @@ -8,7 +8,6 @@
>   #include <drm/drm_drv.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_drv.h"
>   
> @@ -207,8 +206,6 @@ static void mgag200_g200ev_crtc_helper_atomic_enable(struct drm_crtc *crtc,
>   		mgag200_crtc_set_gamma_linear(mdev, format);
>   
>   	mgag200_enable_display(mdev);
> -
> -	drm_crtc_vblank_on(crtc);
>   }
>   
>   static const struct drm_crtc_helper_funcs mgag200_g200ev_crtc_helper_funcs = {
> @@ -216,8 +213,7 @@ static const struct drm_crtc_helper_funcs mgag200_g200ev_crtc_helper_funcs = {
>   	.atomic_check = mgag200_crtc_helper_atomic_check,
>   	.atomic_flush = mgag200_crtc_helper_atomic_flush,
>   	.atomic_enable = mgag200_g200ev_crtc_helper_atomic_enable,
> -	.atomic_disable = mgag200_crtc_helper_atomic_disable,
> -	.get_scanout_position = mgag200_crtc_helper_get_scanout_position,
> +	.atomic_disable = mgag200_crtc_helper_atomic_disable
>   };
>   
>   static const struct drm_crtc_funcs mgag200_g200ev_crtc_funcs = {
> @@ -317,9 +313,5 @@ struct mga_device *mgag200_g200ev_device_create(struct pci_dev *pdev, const stru
>   	drm_mode_config_reset(dev);
>   	drm_kms_helper_poll_init(dev);
>   
> -	ret = drm_vblank_init(dev, 1);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
>   	return mdev;
>   }
> diff --git a/drivers/gpu/drm/mgag200/mgag200_g200ew3.c b/drivers/gpu/drm/mgag200/mgag200_g200ew3.c
> index dabc778e64e8..31624c9ab7b7 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_g200ew3.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_g200ew3.c
> @@ -7,7 +7,6 @@
>   #include <drm/drm_drv.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_drv.h"
>   
> @@ -199,9 +198,5 @@ struct mga_device *mgag200_g200ew3_device_create(struct pci_dev *pdev,
>   	drm_mode_config_reset(dev);
>   	drm_kms_helper_poll_init(dev);
>   
> -	ret = drm_vblank_init(dev, 1);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
>   	return mdev;
>   }
> diff --git a/drivers/gpu/drm/mgag200/mgag200_g200se.c b/drivers/gpu/drm/mgag200/mgag200_g200se.c
> index 9dcbe8304271..7a32d3b1d226 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_g200se.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_g200se.c
> @@ -8,7 +8,6 @@
>   #include <drm/drm_drv.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_drv.h"
>   
> @@ -338,8 +337,6 @@ static void mgag200_g200se_crtc_helper_atomic_enable(struct drm_crtc *crtc,
>   		mgag200_crtc_set_gamma_linear(mdev, format);
>   
>   	mgag200_enable_display(mdev);
> -
> -	drm_crtc_vblank_on(crtc);
>   }
>   
>   static const struct drm_crtc_helper_funcs mgag200_g200se_crtc_helper_funcs = {
> @@ -347,8 +344,7 @@ static const struct drm_crtc_helper_funcs mgag200_g200se_crtc_helper_funcs = {
>   	.atomic_check = mgag200_crtc_helper_atomic_check,
>   	.atomic_flush = mgag200_crtc_helper_atomic_flush,
>   	.atomic_enable = mgag200_g200se_crtc_helper_atomic_enable,
> -	.atomic_disable = mgag200_crtc_helper_atomic_disable,
> -	.get_scanout_position = mgag200_crtc_helper_get_scanout_position,
> +	.atomic_disable = mgag200_crtc_helper_atomic_disable
>   };
>   
>   static const struct drm_crtc_funcs mgag200_g200se_crtc_funcs = {
> @@ -517,9 +513,5 @@ struct mga_device *mgag200_g200se_device_create(struct pci_dev *pdev, const stru
>   	drm_mode_config_reset(dev);
>   	drm_kms_helper_poll_init(dev);
>   
> -	ret = drm_vblank_init(dev, 1);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
>   	return mdev;
>   }
> diff --git a/drivers/gpu/drm/mgag200/mgag200_g200wb.c b/drivers/gpu/drm/mgag200/mgag200_g200wb.c
> index 83a24aedbf2f..a0e7b9ad46cd 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_g200wb.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_g200wb.c
> @@ -8,7 +8,6 @@
>   #include <drm/drm_drv.h>
>   #include <drm/drm_gem_atomic_helper.h>
>   #include <drm/drm_probe_helper.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_drv.h"
>   
> @@ -323,9 +322,5 @@ struct mga_device *mgag200_g200wb_device_create(struct pci_dev *pdev, const stru
>   	drm_mode_config_reset(dev);
>   	drm_kms_helper_poll_init(dev);
>   
> -	ret = drm_vblank_init(dev, 1);
> -	if (ret)
> -		return ERR_PTR(ret);
> -
>   	return mdev;
>   }
> diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
> index 7159909aca1e..fb71658c3117 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_mode.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
> @@ -22,7 +22,6 @@
>   #include <drm/drm_gem_framebuffer_helper.h>
>   #include <drm/drm_panic.h>
>   #include <drm/drm_print.h>
> -#include <drm/drm_vblank.h>
>   
>   #include "mgag200_ddc.h"
>   #include "mgag200_drv.h"
> @@ -227,14 +226,7 @@ void mgag200_set_mode_regs(struct mga_device *mdev, const struct drm_display_mod
>   	vblkstr = mode->crtc_vblank_start;
>   	vblkend = vtotal + 1;
>   
> -	/*
> -	 * There's no VBLANK interrupt on Matrox chipsets, so we use
> -	 * the VLINE interrupt instead. It triggers when the current
> -	 * <linecomp> has been reached. For VBLANK, this is the first
> -	 * non-visible line at the bottom of the screen. Therefore,
> -	 * keep <linecomp> in sync with <vblkstr>.
> -	 */
> -	linecomp = vblkstr;
> +	linecomp = vdispend;
>   
>   	misc = RREG8(MGA_MISC_IN);
>   
> @@ -645,8 +637,6 @@ void mgag200_crtc_helper_atomic_flush(struct drm_crtc *crtc, struct drm_atomic_s
>   	struct mgag200_crtc_state *mgag200_crtc_state = to_mgag200_crtc_state(crtc_state);
>   	struct drm_device *dev = crtc->dev;
>   	struct mga_device *mdev = to_mga_device(dev);
> -	struct drm_pending_vblank_event *event;
> -	unsigned long flags;
>   
>   	if (crtc_state->enable && crtc_state->color_mgmt_changed) {
>   		const struct drm_format_info *format = mgag200_crtc_state->format;
> @@ -656,18 +646,6 @@ void mgag200_crtc_helper_atomic_flush(struct drm_crtc *crtc, struct drm_atomic_s
>   		else
>   			mgag200_crtc_set_gamma_linear(mdev, format);
>   	}
> -
> -	event = crtc->state->event;
> -	if (event) {
> -		crtc->state->event = NULL;
> -
> -		spin_lock_irqsave(&dev->event_lock, flags);
> -		if (drm_crtc_vblank_get(crtc) != 0)
> -			drm_crtc_send_vblank_event(crtc, event);
> -		else
> -			drm_crtc_arm_vblank_event(crtc, event);
> -		spin_unlock_irqrestore(&dev->event_lock, flags);
> -	}
>   }
>   
>   void mgag200_crtc_helper_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_state *old_state)
> @@ -692,44 +670,15 @@ void mgag200_crtc_helper_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_
>   		mgag200_crtc_set_gamma_linear(mdev, format);
>   
>   	mgag200_enable_display(mdev);
> -
> -	drm_crtc_vblank_on(crtc);
>   }
>   
>   void mgag200_crtc_helper_atomic_disable(struct drm_crtc *crtc, struct drm_atomic_state *old_state)
>   {
>   	struct mga_device *mdev = to_mga_device(crtc->dev);
>   
> -	drm_crtc_vblank_off(crtc);
> -
>   	mgag200_disable_display(mdev);
>   }
>   
> -bool mgag200_crtc_helper_get_scanout_position(struct drm_crtc *crtc, bool in_vblank_irq,
> -					      int *vpos, int *hpos,
> -					      ktime_t *stime, ktime_t *etime,
> -					      const struct drm_display_mode *mode)
> -{
> -	struct mga_device *mdev = to_mga_device(crtc->dev);
> -	u32 vcount;
> -
> -	if (stime)
> -		*stime = ktime_get();
> -
> -	if (vpos) {
> -		vcount = RREG32(MGAREG_VCOUNT);
> -		*vpos = vcount & GENMASK(11, 0);
> -	}
> -
> -	if (hpos)
> -		*hpos = mode->htotal >> 1; // near middle of scanline on average
> -
> -	if (etime)
> -		*etime = ktime_get();
> -
> -	return true;
> -}
> -
>   void mgag200_crtc_reset(struct drm_crtc *crtc)
>   {
>   	struct mgag200_crtc_state *mgag200_crtc_state;
> @@ -774,30 +723,6 @@ void mgag200_crtc_atomic_destroy_state(struct drm_crtc *crtc, struct drm_crtc_st
>   	kfree(mgag200_crtc_state);
>   }
>   
> -int mgag200_crtc_enable_vblank(struct drm_crtc *crtc)
> -{
> -	struct mga_device *mdev = to_mga_device(crtc->dev);
> -	u32 ien;
> -
> -	WREG32(MGAREG_ICLEAR, MGAREG_ICLEAR_VLINEICLR);
> -
> -	ien = RREG32(MGAREG_IEN);
> -	ien |= MGAREG_IEN_VLINEIEN;
> -	WREG32(MGAREG_IEN, ien);
> -
> -	return 0;
> -}
> -
> -void mgag200_crtc_disable_vblank(struct drm_crtc *crtc)
> -{
> -	struct mga_device *mdev = to_mga_device(crtc->dev);
> -	u32 ien;
> -
> -	ien = RREG32(MGAREG_IEN);
> -	ien &= ~(MGAREG_IEN_VLINEIEN);
> -	WREG32(MGAREG_IEN, ien);
> -}
> -
>   /*
>    * Mode config
>    */