Re: [PATCH v5 6/7] drm/mgag200: Add vblank support

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

Hi

Am 18.07.24 um 13:34 schrieb Jocelyn Falempe:
> On 18/07/2024 12:44, 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.
> >
> > v5:
> > - disable all interrupts before registering IRQ (Jocelyn)
> > - don't read from ICLEAR (Jocelyn)
> >
> > 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>
> > Tested-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/mgag200/mgag200_drv.c     | 40 +++++++++++++++++
> >   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    | 52 ++++++++++++++++++++++-
> >   drivers/gpu/drm/mgag200/mgag200_reg.h     |  7 +++
> >   12 files changed, 143 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.c 
> > b/drivers/gpu/drm/mgag200/mgag200_drv.c
> > index 62080cf0f2da..c33d4be4ef9d 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 +85,34 @@ 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
> >    */
> > @@ -167,6 +196,7 @@ 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;
> >   @@ -192,6 +222,16 @@ int mgag200_device_init(struct mga_device *mdev,
> >         mutex_unlock(&mdev->rmmio_lock);
> >   +    WREG32(MGAREG_IEN, 0);
> > +    WREG32(MGAREG_ICLEAR, 0);
>
> Writing 0 to iclear has no effect, I think it should be 0x1ff to clear 
> all interrupts, (or 0x1a5 as only bits 0, 2, 5, 7, 8 are defined in 
> the specification).

Errr, sorry. I probably confused it with the IEN register.

In mgag200_crtc_enable_vblank() the driver unconditionally clears the 
VLINE bit in ICLEAR before enabling interrupts. Therefore the write to 
ICLEAR here can be removed entirely.
Best regards Thomas
> with that:
>
> Reviewed-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
>
> > +
> > +    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 f97eaa49b089..829d32f50915 100644
> > --- a/drivers/gpu/drm/mgag200/mgag200_drv.h
> > +++ b/drivers/gpu/drm/mgag200/mgag200_drv.h
> > @@ -411,6 +411,8 @@ 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, \
> > @@ -418,7 +420,9 @@ 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,
> >                  bool set_vidrst);
> > 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 737a48aa9160..6d727ab1a7aa 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"
> >   @@ -315,5 +316,9 @@ 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 8d1ccc2ad94a..e6c9ba61bf97 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"
> >   @@ -320,5 +321,9 @@ 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 265f3e95830a..fbaa97c7e0da 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"
> >   @@ -202,5 +203,9 @@ 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 cf7f6897838f..2a53ebf41539 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"
> >   @@ -520,5 +521,9 @@ 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 e25477347c3e..33ef35c95acb 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"
> >   @@ -326,5 +327,9 @@ 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 ff90f29b0612..afabf693df64 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);
> >   @@ -640,6 +648,8 @@ 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;
> > @@ -649,6 +659,18 @@ 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)
> > @@ -676,12 +698,16 @@ void mgag200_crtc_helper_atomic_enable(struct 
> > drm_crtc *crtc, struct drm_atomic_
> >         if (mdev->info->sync_bmc)
> >           mgag200_bmc_start_scanout(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);
> > +
> >       if (mdev->info->sync_bmc)
> >           mgag200_bmc_stop_scanout(mdev);
> >   @@ -732,6 +758,30 @@ 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
> >    */
> > 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

--
--
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)