Re: [Intel-gfx] [PATCH 04/37] drm/i915: rework locking for intel_dpio|sbi_read|write

On Wed, 12 Dec 2012 14:06:44 +0100 Daniel Vetter daniel.vetter@ffwll.ch wrote:

Spinning for up to 200 us with interrupts locked out is not good. So let's just spin (and even that seems to be excessive).

And we don't call these functions from interrupt context, so this is not required. Besides that doing anything in interrupt contexts which might take a few hundred us is a no-go. So just convert the entire thing to a mutex. Also move the mutex-grabbing out of the read/write functions (add a WARN_ON(!is_locked)) instead) since all callers are nicely grouped together.

Finally the real motivation for this change: Dont grab the modeset mutex in the dpio debugfs file, we don't need that consistency. And correctness of the dpio interface is ensured with the dpio_lock.

Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch

drivers/gpu/drm/i915/i915_debugfs.c | 4 +-- drivers/gpu/drm/i915/i915_dma.c | 2 +- drivers/gpu/drm/i915/i915_drv.h | 2 +- drivers/gpu/drm/i915/intel_display.c | 53 ++++++++++++++-------------------- 4 files changed, 25 insertions(+), 36 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c index 58e6676..35d2ace 100644 --- a/drivers/gpu/drm/i915/i915_debugfs.c +++ b/drivers/gpu/drm/i915/i915_debugfs.c @@ -1553,7 +1553,7 @@ static int i915_dpio_info(struct seq_file *m, void *data) return 0; }

• ret = mutex_lock_interruptible(&dev->mode_config.mutex);

• ret = mutex_lock_interruptible(&dev_priv->dpio_lock); if (ret) return ret;

@@ -1582,7 +1582,7 @@ static int i915_dpio_info(struct seq_file *m, void *data) seq_printf(m, "DPIO_FASTCLK_DISABLE: 0x%08x\n", intel_dpio_read(dev_priv, DPIO_FASTCLK_DISABLE));

• mutex_unlock(&dev->mode_config.mutex);

• mutex_unlock(&dev_priv->dpio_lock);

  return 0;

} diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c index 2635ee6..ad488f6 100644 --- a/drivers/gpu/drm/i915/i915_dma.c +++ b/drivers/gpu/drm/i915/i915_dma.c @@ -1579,7 +1579,7 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags) spin_lock_init(&dev_priv->irq_lock); spin_lock_init(&dev_priv->error_lock); spin_lock_init(&dev_priv->rps.lock);

• spin_lock_init(&dev_priv->dpio_lock);

• mutex_init(&dev_priv->dpio_lock);

  mutex_init(&dev_priv->rps.hw_lock);

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index e2944e9..6fa0c00 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -655,7 +655,7 @@ typedef struct drm_i915_private { spinlock_t irq_lock;

/* DPIO indirect register protection */

• spinlock_t dpio_lock;

• struct mutex dpio_lock;

  /** Cached value of IMR to avoid reads in updating the bitfield */ u32 pipestat[2];

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c index d303f2a..a0d8869 100644 --- a/drivers/gpu/drm/i915/intel_display.c +++ b/drivers/gpu/drm/i915/intel_display.c @@ -416,13 +416,11 @@ static const intel_limit_t intel_limits_vlv_dp = {

u32 intel_dpio_read(struct drm_i915_private *dev_priv, int reg) {

• unsigned long flags;
• u32 val = 0;

• WARN_ON(!mutex_is_locked(&dev_priv->dpio_lock));

• spin_lock_irqsave(&dev_priv->dpio_lock, flags); if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100)) { DRM_ERROR("DPIO idle wait timed out\n");

• goto out_unlock;
  

• return 0;
  

  }

  I915_WRITE(DPIO_REG, reg);

@@ -430,24 +428,20 @@ u32 intel_dpio_read(struct drm_i915_private *dev_priv, int reg) DPIO_BYTE); if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100)) { DRM_ERROR("DPIO read wait timed out\n");

• goto out_unlock;
  

• return 0;
  

  }

• val = I915_READ(DPIO_DATA);

-out_unlock:

• spin_unlock_irqrestore(&dev_priv->dpio_lock, flags);
• return val;

• return I915_READ(DPIO_DATA);

}

static void intel_dpio_write(struct drm_i915_private *dev_priv, int reg, u32 val) {

• unsigned long flags;

• WARN_ON(!mutex_is_locked(&dev_priv->dpio_lock));

• spin_lock_irqsave(&dev_priv->dpio_lock, flags); if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100)) { DRM_ERROR("DPIO idle wait timed out\n");

• goto out_unlock;
  

• return;
  

  }

  I915_WRITE(DPIO_DATA, val);

@@ -456,9 +450,6 @@ static void intel_dpio_write(struct drm_i915_private *dev_priv, int reg, DPIO_BYTE); if (wait_for_atomic_us((I915_READ(DPIO_PKT) & DPIO_BUSY) == 0, 100)) DRM_ERROR("DPIO write wait timed out\n");

-out_unlock:

•   spin_unlock_irqrestore(&dev_priv->dpio_lock, flags);
  

}

static void vlv_init_dpio(struct drm_device *dev) @@ -1455,13 +1446,12 @@ static void intel_disable_pll(struct drm_i915_private *dev_priv, enum pipe pipe) static void intel_sbi_write(struct drm_i915_private *dev_priv, u16 reg, u32 value) {

• unsigned long flags;

• WARN_ON(!mutex_is_locked(&dev_priv->dpio_lock));

• spin_lock_irqsave(&dev_priv->dpio_lock, flags); if (wait_for((I915_READ(SBI_CTL_STAT) & SBI_BUSY) == 0, 100)) { DRM_ERROR("timeout waiting for SBI to become ready\n");

• goto out_unlock;
  

• return;
  

  }

  I915_WRITE(SBI_ADDR,

@@ -1475,24 +1465,19 @@ intel_sbi_write(struct drm_i915_private *dev_priv, u16 reg, u32 value) if (wait_for((I915_READ(SBI_CTL_STAT) & (SBI_BUSY | SBI_RESPONSE_FAIL)) == 0, 100)) { DRM_ERROR("timeout waiting for SBI to complete write transaction\n");

• goto out_unlock;
  

• return;
  

  }

-out_unlock:

• spin_unlock_irqrestore(&dev_priv->dpio_lock, flags);

}

static u32 intel_sbi_read(struct drm_i915_private *dev_priv, u16 reg) {

• unsigned long flags;
• u32 value = 0;

• WARN_ON(!mutex_is_locked(&dev_priv->dpio_lock));

• spin_lock_irqsave(&dev_priv->dpio_lock, flags); if (wait_for((I915_READ(SBI_CTL_STAT) & SBI_BUSY) == 0, 100)) { DRM_ERROR("timeout waiting for SBI to become ready\n");

• goto out_unlock;
  

• return 0;
  

  }

  I915_WRITE(SBI_ADDR,

@@ -1504,14 +1489,10 @@ intel_sbi_read(struct drm_i915_private *dev_priv, u16 reg) if (wait_for((I915_READ(SBI_CTL_STAT) & (SBI_BUSY | SBI_RESPONSE_FAIL)) == 0, 100)) { DRM_ERROR("timeout waiting for SBI to complete read transaction\n");

• goto out_unlock;
  

• return 0;
  

  }

• value = I915_READ(SBI_DATA);

-out_unlock:

• spin_unlock_irqrestore(&dev_priv->dpio_lock, flags);
• return value;

• return I915_READ(SBI_DATA);

}

/** @@ -2960,6 +2941,8 @@ static void lpt_program_iclkip(struct drm_crtc *crtc) u32 divsel, phaseinc, auxdiv, phasedir = 0; u32 temp;

• mutex_lock(&dev_priv->dpio_lock);
• /* It is necessary to ungate the pixclk gate prior to programming
  • the divisors, and gate it back when it is done.
  */

@@ -3041,6 +3024,8 @@ static void lpt_program_iclkip(struct drm_crtc *crtc) udelay(24);

I915_WRITE(PIXCLK_GATE, PIXCLK_GATE_UNGATE);

• mutex_unlock(&dev_priv->dpio_lock);

}

/* @@ -4268,6 +4253,8 @@ static void vlv_update_pll(struct drm_crtc *crtc, bool is_sdvo; u32 temp;

• mutex_lock(&dev_priv->dpio_lock);
• is_sdvo = intel_pipe_has_type(crtc, INTEL_OUTPUT_SDVO) || intel_pipe_has_type(crtc, INTEL_OUTPUT_HDMI);

@@ -4351,6 +4338,8 @@ static void vlv_update_pll(struct drm_crtc *crtc, temp |= (1 << 21); intel_dpio_write(dev_priv, DPIO_DATA_CHANNEL2, temp); }

• mutex_unlock(&dev_priv->dpio_lock);

}

static void i9xx_update_pll(struct drm_crtc *crtc,

Looks fine, I guess you could convert the wait_for_atomic_us to the non-atomic variant now that you have a mutex. Either way:

Reviewed-by: Jesse Barnes jbarnes@virtuousgeek.org