Re: [PATCH 2/2] drm/mgag200: Add vblank support

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Hi

thanks for the feedback.

Am 10.09.19 um 16:01 schrieb Ville Syrjälä:
> On Mon, Sep 09, 2019 at 04:06:33PM +0200, Thomas Zimmermann wrote:
>> Support for vblank requires VSYNC to signal an interrupt, which is broken
>> on Matrox chipsets.
> 
> I don't remember there being anything wrong with the vsync interrupt.
> What makes you think it's broken?

I tested vsync with the same code as in this patch, with extra spin
locks to protect against concurrent register access (vsync uses crtc11h).

A few things constantly went wrong: I never received it when setting
linecomp to vdisplay. However it fired when linecomp was ~0. Then I
regularly missed the first interrupt (but only the first), and
occasionally my test system crashed when I entered commands on the
serial terminal. The vsync irq is maybe not entirely broken, but appears
to be much harder to get right.

>> The workaround that is used here and in other free
>> Matrox drivers is to program <linecomp> to the value of <vdisplay> and
>> enable the VLINE interrupt. This triggers an interrupt at the same time
>> when VSYNC begins.
> 
> You're programming it to fire at start of vblank, not start of vsync.

Ah, sorry for messing up terminology; will be fixed. No matter what's
wrong with the vsync irq: there's no vblank irq, so using linecomp
should be the way to go in any case.

> 
>>
>> VLINE uses separate registers for enabling and clearing pending interrupts.
>> No extra syncronization between irq handler and the rest of the driver is
>> required.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
>> ---
>>  drivers/gpu/drm/mgag200/mgag200_drv.c  |  1 +
>>  drivers/gpu/drm/mgag200/mgag200_drv.h  |  1 +
>>  drivers/gpu/drm/mgag200/mgag200_main.c | 33 ++++++++++++++++++++
>>  drivers/gpu/drm/mgag200/mgag200_mode.c | 42 +++++++++++++++++++++++---
>>  4 files changed, 73 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c b/drivers/gpu/drm/mgag200/mgag200_drv.c
>> index 4f9df3b93598..cff265973154 100644
>> --- a/drivers/gpu/drm/mgag200/mgag200_drv.c
>> +++ b/drivers/gpu/drm/mgag200/mgag200_drv.c
>> @@ -67,6 +67,7 @@ static struct drm_driver driver = {
>>  	.driver_features = DRIVER_GEM | DRIVER_MODESET,
>>  	.load = mgag200_driver_load,
>>  	.unload = mgag200_driver_unload,
>> +	.irq_handler = mgag200_irq_handler,
>>  	.fops = &mgag200_driver_fops,
>>  	.name = DRIVER_NAME,
>>  	.desc = DRIVER_DESC,
>> diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.h b/drivers/gpu/drm/mgag200/mgag200_drv.h
>> index 1c93f8dc08c7..88cf256d135f 100644
>> --- a/drivers/gpu/drm/mgag200/mgag200_drv.h
>> +++ b/drivers/gpu/drm/mgag200/mgag200_drv.h
>> @@ -195,6 +195,7 @@ void mgag200_modeset_fini(struct mga_device *mdev);
>>  				/* mgag200_main.c */
>>  int mgag200_driver_load(struct drm_device *dev, unsigned long flags);
>>  void mgag200_driver_unload(struct drm_device *dev);
>> +irqreturn_t mgag200_irq_handler(int irq, void *arg);
>>  
>>  				/* mgag200_i2c.c */
>>  struct mga_i2c_chan *mgag200_i2c_create(struct drm_device *dev);
>> diff --git a/drivers/gpu/drm/mgag200/mgag200_main.c b/drivers/gpu/drm/mgag200/mgag200_main.c
>> index a9773334dedf..5941607796e8 100644
>> --- a/drivers/gpu/drm/mgag200/mgag200_main.c
>> +++ b/drivers/gpu/drm/mgag200/mgag200_main.c
>> @@ -10,7 +10,9 @@
>>  
>>  #include <drm/drm_crtc_helper.h>
>>  #include <drm/drm_gem_framebuffer_helper.h>
>> +#include <drm/drm_irq.h>
>>  #include <drm/drm_pci.h>
>> +#include <drm/drm_vblank.h>
>>  
>>  #include "mgag200_drv.h"
>>  
>> @@ -186,10 +188,18 @@ int mgag200_driver_load(struct drm_device *dev, unsigned long flags)
>>  	}
>>  	mdev->cursor.pixels_current = NULL;
>>  
>> +	r = drm_vblank_init(dev, 1);
>> +	if (r)
>> +		goto err_modeset;
>> +
>>  	r = drm_fbdev_generic_setup(mdev->dev, 0);
>>  	if (r)
>>  		goto err_modeset;
>>  
>> +	r = drm_irq_install(dev, dev->pdev->irq);
>> +	if (r)
>> +		goto err_modeset;
>> +
>>  	return 0;
>>  
>>  err_modeset:
>> @@ -207,8 +217,31 @@ void mgag200_driver_unload(struct drm_device *dev)
>>  
>>  	if (mdev == NULL)
>>  		return;
>> +	drm_irq_uninstall(dev);
>>  	mgag200_modeset_fini(mdev);
>>  	drm_mode_config_cleanup(dev);
>>  	mgag200_mm_fini(mdev);
>>  	dev->dev_private = NULL;
>>  }
>> +
>> +irqreturn_t mgag200_irq_handler(int irq, void *arg)
>> +{
>> +	struct drm_device *dev = arg;
>> +	struct mga_device *mdev = dev->dev_private;
>> +	struct drm_crtc *crtc;
>> +	u32 status, iclear;
>> +
>> +	status = RREG32(0x1e14);
>> +
>> +	if (status & 0x00000020) { /* test <vlinepen> */
>> +		drm_for_each_crtc(crtc, dev) {
>> +			drm_crtc_handle_vblank(crtc);
>> +		}
> 
> A bit odd way to write that but as long this driver doesn't support
> crtc2 it should be fine.
> 
>> +		iclear = RREG32(0x1e18);
>> +		iclear |= 0x00000020; /* set <vlineiclr> */
>> +		WREG32(0x1e18, iclear);
>> +		return IRQ_HANDLED;
>> +	}
>> +
>> +	return IRQ_NONE;
>> +};
>> diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
>> index 5e778b5f1a10..ffe5f15d0a7d 100644
>> --- a/drivers/gpu/drm/mgag200/mgag200_mode.c
>> +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
>> @@ -905,6 +905,7 @@ static int mga_crtc_mode_set(struct drm_crtc *crtc,
>>  	const struct drm_framebuffer *fb = crtc->primary->fb;
>>  	int hdisplay, hsyncstart, hsyncend, htotal;
>>  	int vdisplay, vsyncstart, vsyncend, vtotal;
>> +	int linecomp;
>>  	int pitch;
>>  	int option = 0, option2 = 0;
>>  	int i;
>> @@ -1042,6 +1043,13 @@ static int mga_crtc_mode_set(struct drm_crtc *crtc,
>>  	vsyncend = mode->vsync_end - 1;
>>  	vtotal = mode->vtotal - 2;
>>  
>> +	/* The VSYNC interrupt is broken on Matrox chipsets. We use
>> +	 * the VLINE interrupt instead. It triggers when the current
>> +	 * linecomp has been reached. Therefore keep <linecomp> in
>> +	 * sync with <vdisplay>.
>> +	 */
>> +	linecomp = vdisplay;
> 
> I have an odd recollection that you want vdisplay+1 here if you
> want the interrupt to fire at the correct time.
> 
> Sine linecomp also resets the memory address counter to 0 you
> should probably see one bogus line at the bottom of the screen
> if my recollection of that +1 is correct.

It works reliably on my test system, but I'll double-check against
existing drivers.

> But maybe my memory is wrong.
> 
>> +
>>  	WREG_GFX(0, 0);
>>  	WREG_GFX(1, 0);
>>  	WREG_GFX(2, 0);
>> @@ -1063,12 +1071,12 @@ static int mga_crtc_mode_set(struct drm_crtc *crtc,
>>  		 ((vdisplay & 0x100) >> 7) |
>>  		 ((vsyncstart & 0x100) >> 6) |
>>  		 ((vdisplay & 0x100) >> 5) |
>> -		 ((vdisplay & 0x100) >> 4) | /* linecomp */
>> +		 ((linecomp & 0x100) >> 4) |
>>  		 ((vtotal & 0x200) >> 4)|
>>  		 ((vdisplay & 0x200) >> 3) |
>>  		 ((vsyncstart & 0x200) >> 2));
>>  	WREG_CRT(9, ((vdisplay & 0x200) >> 4) |
>> -		 ((vdisplay & 0x200) >> 3));
>> +		 ((linecomp & 0x200) >> 3));
>>  	WREG_CRT(10, 0);
>>  	WREG_CRT(11, 0);
>>  	WREG_CRT(12, 0);
>> @@ -1083,7 +1091,7 @@ static int mga_crtc_mode_set(struct drm_crtc *crtc,
>>  	WREG_CRT(21, vdisplay & 0xFF);
>>  	WREG_CRT(22, (vtotal + 1) & 0xFF);
>>  	WREG_CRT(23, 0xc3);
>> -	WREG_CRT(24, vdisplay & 0xFF);
>> +	WREG_CRT(24, linecomp & 0xff);
>>  
>>  	ext_vga[0] = 0;
>>  	ext_vga[5] = 0;
>> @@ -1099,7 +1107,7 @@ static int mga_crtc_mode_set(struct drm_crtc *crtc,
>>  		((vdisplay & 0x400) >> 8) |
>>  		((vdisplay & 0xc00) >> 7) |
>>  		((vsyncstart & 0xc00) >> 5) |
>> -		((vdisplay & 0x400) >> 3);
>> +		((linecomp & 0x400) >> 3);
>>  	if (fb->format->cpp[0] * 8 == 24)
>>  		ext_vga[3] = (((1 << bppshift) * 3) - 1) | 0x80;
>>  	else
>> @@ -1411,6 +1419,30 @@ static void mga_crtc_disable(struct drm_crtc *crtc)
>>  	crtc->primary->fb = NULL;
>>  }
>>  
>> +static int mga_crtc_enable_vblank(struct drm_crtc *crtc)
>> +{
>> +	struct drm_device *dev = crtc->dev;
>> +	struct mga_device *mdev = dev->dev_private;
>> +	u32 ien;
>> +
>> +	ien = RREG32(0x1e1c);
> 
> MGAREG_IEN?

I'll go through the changes and use constants everywhere.

Best regards
Thomas

>> +	ien |= 0x00000020; /* set <vlineien> */
>> +	WREG32(0x1e1c, ien);
>> +
>> +	return 0;
>> +}
>> +
>> +static void mga_crtc_disable_vblank(struct drm_crtc *crtc)
>> +{
>> +	struct drm_device *dev = crtc->dev;
>> +	struct mga_device *mdev = dev->dev_private;
>> +	u32 ien;
>> +
>> +	ien = RREG32(0x1e1c);
>> +	ien &= 0xffffffdf; /* clear <vlineien> */
>> +	WREG32(0x1e1c, ien);
>> +}
>> +
>>  /* These provide the minimum set of functions required to handle a CRTC */
>>  static const struct drm_crtc_funcs mga_crtc_funcs = {
>>  	.cursor_set = mga_crtc_cursor_set,
>> @@ -1418,6 +1450,8 @@ static const struct drm_crtc_funcs mga_crtc_funcs = {
>>  	.gamma_set = mga_crtc_gamma_set,
>>  	.set_config = drm_crtc_helper_set_config,
>>  	.destroy = mga_crtc_destroy,
>> +	.enable_vblank = mga_crtc_enable_vblank,
>> +	.disable_vblank = mga_crtc_disable_vblank,
>>  };
>>  
>>  static const struct drm_crtc_helper_funcs mga_helper_funcs = {
>> -- 
>> 2.23.0
>>
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@xxxxxxxxxxxxxxxxxxxxx
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)

Attachment: signature.asc
Description: OpenPGP digital signature

_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel

[Index of Archives]     [Linux DRI Users]     [Linux Intel Graphics]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux