Re: [PATCH v4 6/7] drm/mgag200: Add vblank support

Thomas Zimmermann <tzimmermann@xxxxxxx> · Wed, 17 Jul 2024 19:10:48 +0200

Hi

Am 08.07.24 um 14:46 schrieb Jocelyn Falempe:


On 05/07/2024 13:47, Thomas Zimmermann wrote:
There's no VBLANK interrupt on Matrox chipsets. The workaround that is
being used here and in other free Matrox drivers is to program 
<linecomp>
to the value of <vblkstr> and enable the VLINE interrupt. This triggers
an interrupt at the time when VBLANK begins.

VLINE uses separate registers for enabling and clearing pending 
interrupts.
No extra synchronization between irq handler and the rest of the 
driver is
required.

Thanks for this patch, I have a few comments below:

v4:
- recreate patch on latest upstream
- use devm_request_irq() for managed cleanup
- fail if vblanking cannot be initialized
- rename register constants (Sam, Emil)
- clear interrupt before registering handler (Ville)
- move <linecomp> programming into separate commit
- set <linecomp> to <vblkstr>
- fix typo in commit message

v3:
- set <linecomp> to <vdisplay> + 1 to trigger at VBLANK
- expand comment on linecomp

v2:
- only signal vblank on CRTC 0
- use constants for registers and fields
- set VLINECLR before enabling interrupt
- test against STATUS and IEN in irq handler
- coding-style fixes

Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Acked-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
Acked-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
---
  drivers/gpu/drm/mgag200/mgag200_drv.c     | 47 ++++++++++++++++++++
  drivers/gpu/drm/mgag200/mgag200_drv.h     |  6 ++-
  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  |  5 +++
  drivers/gpu/drm/mgag200/mgag200_g200ev.c  |  5 +++
  drivers/gpu/drm/mgag200/mgag200_g200ew3.c |  5 +++
  drivers/gpu/drm/mgag200/mgag200_g200se.c  |  5 +++
  drivers/gpu/drm/mgag200/mgag200_g200wb.c  |  5 +++
  drivers/gpu/drm/mgag200/mgag200_mode.c    | 54 ++++++++++++++++++++++-
  drivers/gpu/drm/mgag200/mgag200_reg.h     |  7 +++
  12 files changed, 152 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c 
b/drivers/gpu/drm/mgag200/mgag200_drv.c
index 62080cf0f2da..62479de9e659 100644
--- a/drivers/gpu/drm/mgag200/mgag200_drv.c
+++ b/drivers/gpu/drm/mgag200/mgag200_drv.c
@@ -18,6 +18,7 @@
  #include <drm/drm_managed.h>
  #include <drm/drm_module.h>
  #include <drm/drm_pciids.h>
+#include <drm/drm_vblank.h>
    #include "mgag200_drv.h"
  @@ -84,6 +85,35 @@ 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, iclear;
+
+    status = RREG32(MGAREG_STATUS);
+
+    if (status & MGAREG_STATUS_VLINEPEN) {
+        ien = RREG32(MGAREG_IEN);
+        if (!(ien & MGAREG_IEN_VLINEIEN))
+            goto out;
+
This is to catch a race condition, receiving the interrupt, just after 
disabling it ? I think you still want to clear it, to avoid having it 
fire as soon as you re-enable it ?

Shared interrupts (with another device) can bring us here. I was 
thinking that we might have stale state on the Matrox device (i.e., 
VLINEIEN is off, but the VLINEPEN status bit is stil set). So it checks 
whether the VLINE interrupt is really on.


+        crtc = drm_crtc_from_index(dev, 0);
+        if (WARN_ON_ONCE(!crtc))
+            goto out;
+        drm_crtc_handle_vblank(crtc);
+
+        iclear = RREG32(MGAREG_ICLEAR);

iclear is a Write-Only register, according to the documentation.
So reading it will always return 0.

I would suggest to just write:

WREG32(MGAREG_ICLEAR, MGAREG_ICLEAR_VLINEICLR);

+        iclear |= MGAREG_ICLEAR_VLINEICLR;
+        WREG32(MGAREG_ICLEAR, iclear);
+        return IRQ_HANDLED;
+    }
+
+out:
+    return IRQ_NONE;
+}
+
  /*
   * DRM driver
   */
@@ -167,7 +197,9 @@ 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;
+    u32 ien, iclear;
      int ret;
        mdev->info = info;
@@ -192,6 +224,21 @@ int mgag200_device_init(struct mga_device *mdev,
        mutex_unlock(&mdev->rmmio_lock);
  +    ien = RREG32(MGAREG_IEN);
+    ien &= ~(MGAREG_IEN_VLINEIEN);
+    WREG32(MGAREG_IEN, ien);

I would suggest to disable all interrupt instead,
WREG32(MGAREG_IEN, 0);



+
+    iclear = RREG32(MGAREG_ICLEAR);

same here, don't read the iclear register.

+    iclear |= MGAREG_ICLEAR_VLINEICLR;
+    WREG32(MGAREG_ICLEAR, iclear);
+
+    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 7f7dfbd0f013..f7b22b195016 100644
--- a/drivers/gpu/drm/mgag200/mgag200_drv.h
+++ b/drivers/gpu/drm/mgag200/mgag200_drv.h
@@ -421,6 +421,8 @@ void mgag200_crtc_helper_atomic_disable(struct 
drm_crtc *crtc, struct drm_atomic
  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, \
@@ -428,7 +430,9 @@ void mgag200_crtc_atomic_destroy_state(struct 
drm_crtc *crtc, struct drm_crtc_st
      .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
+    .atomic_destroy_state = mgag200_crtc_atomic_destroy_state, \
+    .enable_vblank = mgag200_crtc_enable_vblank, \
+    .disable_vblank = mgag200_crtc_disable_vblank
    void mgag200_set_mode_regs(struct mga_device *mdev, const struct 
drm_display_mode *mode);
  void mgag200_set_format_regs(struct mga_device *mdev, const struct 
drm_format_info *format);
diff --git a/drivers/gpu/drm/mgag200/mgag200_g200.c 
b/drivers/gpu/drm/mgag200/mgag200_g200.c
index f874e2949840..77ce8d36cef0 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200.c
@@ -8,6 +8,7 @@
  #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"
  @@ -403,5 +404,9 @@ 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 52bf49ead5c5..72bd8e3421c2 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200eh.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200eh.c
@@ -8,6 +8,7 @@
  #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"
  @@ -279,5 +280,9 @@ 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 e7f89b2a59fd..1bbb0745b84a 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200eh3.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200eh3.c
@@ -7,6 +7,7 @@
  #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"
  @@ -184,5 +185,9 @@ 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 4e8a1756138d..3350baf08a45 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200er.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200er.c
@@ -8,6 +8,7 @@
  #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"
  @@ -318,5 +319,9 @@ 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 d884f3cb0ec7..88d8bcd6fe51 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200ev.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200ev.c
@@ -8,6 +8,7 @@
  #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"
  @@ -323,5 +324,9 @@ 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 839401e8b465..9d08180f7612 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200ew3.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200ew3.c
@@ -7,6 +7,7 @@
  #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"
  @@ -204,5 +205,9 @@ 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 a824bb8ad579..fcc8075627ef 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200se.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200se.c
@@ -8,6 +8,7 @@
  #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"
  @@ -523,5 +524,9 @@ 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 835df0f4fc13..4f8ef3465b9f 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200wb.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200wb.c
@@ -8,6 +8,7 @@
  #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"
  @@ -328,5 +329,9 @@ 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 da2cbe81d4e6..ec6fb1277d6e 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -22,6 +22,7 @@
  #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"
@@ -226,7 +227,14 @@ void mgag200_set_mode_regs(struct mga_device 
*mdev, const struct drm_display_mod
      vblkstr = mode->crtc_vblank_start;
      vblkend = vtotal + 1;
  -    linecomp = vdispend;
+    /*
+     * 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;
        misc = RREG8(MGA_MISC_IN);
  @@ -637,6 +645,8 @@ 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;
@@ -646,6 +656,18 @@ 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)
@@ -676,6 +698,8 @@ void mgag200_crtc_helper_atomic_enable(struct 
drm_crtc *crtc, struct drm_atomic_
        if (funcs->enable_vidrst)
          funcs->enable_vidrst(mdev);
+
+    drm_crtc_vblank_on(crtc);
  }
    void mgag200_crtc_helper_atomic_disable(struct drm_crtc *crtc, 
struct drm_atomic_state *old_state)
@@ -683,6 +707,8 @@ void mgag200_crtc_helper_atomic_disable(struct 
drm_crtc *crtc, struct drm_atomic
      struct mga_device *mdev = to_mga_device(crtc->dev);
      const struct mgag200_device_funcs *funcs = mdev->funcs;
  +    drm_crtc_vblank_off(crtc);
+
      if (funcs->disable_vidrst)
          funcs->disable_vidrst(mdev);
  @@ -735,6 +761,32 @@ 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 iclear, ien;
+
+    iclear = RREG32(MGAREG_ICLEAR);
+    iclear |= MGAREG_ICLEAR_VLINEICLR;
+    WREG32(MGAREG_ICLEAR, iclear);

same here, don't read the iclear register.

+
+    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
   */
diff --git a/drivers/gpu/drm/mgag200/mgag200_reg.h 
b/drivers/gpu/drm/mgag200/mgag200_reg.h
index aa73463674e4..d4fef8f25871 100644
--- a/drivers/gpu/drm/mgag200/mgag200_reg.h
+++ b/drivers/gpu/drm/mgag200/mgag200_reg.h
@@ -102,10 +102,17 @@
  #define MGAREG_EXEC        0x0100
    #define    MGAREG_FIFOSTATUS    0x1e10
+
  #define    MGAREG_STATUS        0x1e14
+#define MGAREG_STATUS_VLINEPEN    BIT(5)
+
  #define MGAREG_CACHEFLUSH       0x1fff
+
  #define    MGAREG_ICLEAR        0x1e18
+#define MGAREG_ICLEAR_VLINEICLR    BIT(5)
+
  #define    MGAREG_IEN        0x1e1c
+#define MGAREG_IEN_VLINEIEN    BIT(5)
    #define    MGAREG_VCOUNT        0x1e20


Do you know what happens if the IRQ doesn't work (ie not receiving any 
IRQ)?
When testing the DMA, I remember that on a few machines, I never get 
the Softrap IRQ. I don't know if it was a DMA engine problem, or if 
it's the mgag200 IRQ that was not connected properly.

I will try to find this machine, and test this series on it.

Best regards,


--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)







