[PATCH 2/2] drm/mgag200: Add vblank support
Thomas Zimmermann
tzimmermann at suse.de
Tue Sep 10 14:38:50 UTC 2019
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 at suse.de>
>> ---
>> 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 at lists.freedesktop.org
>> 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)
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