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drm/i915: Take forcewake once for the entire GMBUS transaction
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As we do many register reads within a very short period of time, hold
the GMBUS powerwell from start to finish.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Weinehall <david.weinehall@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160819164503.17845-1-chris@chris-wilson.co.uk
Reviewed-by: David Weinehall <david.weinehall@linux.intel.com>
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Chris Wilson committed Aug 22, 2016
1 parent 637ee29 commit 4e6c2d5
Showing 1 changed file with 63 additions and 68 deletions.
131 changes: 63 additions & 68 deletions drivers/gpu/drm/i915/intel_i2c.c
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Original file line number Diff line number Diff line change
Expand Up @@ -255,90 +255,81 @@ intel_gpio_setup(struct intel_gmbus *bus, unsigned int pin)
algo->data = bus;
}

static int
gmbus_wait_hw_status(struct drm_i915_private *dev_priv,
u32 gmbus2_status,
u32 gmbus4_irq_en)
static int gmbus_wait(struct drm_i915_private *dev_priv, u32 status, u32 irq_en)
{
int i;
u32 gmbus2 = 0;
DEFINE_WAIT(wait);

if (!HAS_GMBUS_IRQ(dev_priv))
gmbus4_irq_en = 0;
u32 gmbus2;
int ret;

/* Important: The hw handles only the first bit, so set only one! Since
* we also need to check for NAKs besides the hw ready/idle signal, we
* need to wake up periodically and check that ourselves. */
I915_WRITE(GMBUS4, gmbus4_irq_en);

for (i = 0; i < msecs_to_jiffies_timeout(50); i++) {
prepare_to_wait(&dev_priv->gmbus_wait_queue, &wait,
TASK_UNINTERRUPTIBLE);
* need to wake up periodically and check that ourselves.
*/
if (!HAS_GMBUS_IRQ(dev_priv))
irq_en = 0;

gmbus2 = I915_READ_NOTRACE(GMBUS2);
if (gmbus2 & (GMBUS_SATOER | gmbus2_status))
break;
add_wait_queue(&dev_priv->gmbus_wait_queue, &wait);
I915_WRITE_FW(GMBUS4, irq_en);

schedule_timeout(1);
}
finish_wait(&dev_priv->gmbus_wait_queue, &wait);
status |= GMBUS_SATOER;
ret = wait_for_us((gmbus2 = I915_READ_FW(GMBUS2)) & status, 2);
if (ret)
ret = wait_for((gmbus2 = I915_READ_FW(GMBUS2)) & status, 50);

I915_WRITE(GMBUS4, 0);
I915_WRITE_FW(GMBUS4, 0);
remove_wait_queue(&dev_priv->gmbus_wait_queue, &wait);

if (gmbus2 & GMBUS_SATOER)
return -ENXIO;
if (gmbus2 & gmbus2_status)
return 0;
return -ETIMEDOUT;

return ret;
}

static int
gmbus_wait_idle(struct drm_i915_private *dev_priv)
{
DEFINE_WAIT(wait);
u32 irq_enable;
int ret;

if (!HAS_GMBUS_IRQ(dev_priv))
return intel_wait_for_register(dev_priv,
GMBUS2, GMBUS_ACTIVE, 0,
10);

/* Important: The hw handles only the first bit, so set only one! */
I915_WRITE(GMBUS4, GMBUS_IDLE_EN);
irq_enable = 0;
if (HAS_GMBUS_IRQ(dev_priv))
irq_enable = GMBUS_IDLE_EN;

ret = wait_event_timeout(dev_priv->gmbus_wait_queue,
(I915_READ_NOTRACE(GMBUS2) & GMBUS_ACTIVE) == 0,
msecs_to_jiffies_timeout(10));
add_wait_queue(&dev_priv->gmbus_wait_queue, &wait);
I915_WRITE_FW(GMBUS4, irq_enable);

I915_WRITE(GMBUS4, 0);
ret = intel_wait_for_register_fw(dev_priv,
GMBUS2, GMBUS_ACTIVE, 0,
10);

if (ret)
return 0;
else
return -ETIMEDOUT;
I915_WRITE_FW(GMBUS4, 0);
remove_wait_queue(&dev_priv->gmbus_wait_queue, &wait);

return ret;
}

static int
gmbus_xfer_read_chunk(struct drm_i915_private *dev_priv,
unsigned short addr, u8 *buf, unsigned int len,
u32 gmbus1_index)
{
I915_WRITE(GMBUS1,
gmbus1_index |
GMBUS_CYCLE_WAIT |
(len << GMBUS_BYTE_COUNT_SHIFT) |
(addr << GMBUS_SLAVE_ADDR_SHIFT) |
GMBUS_SLAVE_READ | GMBUS_SW_RDY);
I915_WRITE_FW(GMBUS1,
gmbus1_index |
GMBUS_CYCLE_WAIT |
(len << GMBUS_BYTE_COUNT_SHIFT) |
(addr << GMBUS_SLAVE_ADDR_SHIFT) |
GMBUS_SLAVE_READ | GMBUS_SW_RDY);
while (len) {
int ret;
u32 val, loop = 0;

ret = gmbus_wait_hw_status(dev_priv, GMBUS_HW_RDY,
GMBUS_HW_RDY_EN);
ret = gmbus_wait(dev_priv, GMBUS_HW_RDY, GMBUS_HW_RDY_EN);
if (ret)
return ret;

val = I915_READ(GMBUS3);
val = I915_READ_FW(GMBUS3);
do {
*buf++ = val & 0xff;
val >>= 8;
Expand Down Expand Up @@ -385,12 +376,12 @@ gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv,
len -= 1;
}

I915_WRITE(GMBUS3, val);
I915_WRITE(GMBUS1,
GMBUS_CYCLE_WAIT |
(chunk_size << GMBUS_BYTE_COUNT_SHIFT) |
(addr << GMBUS_SLAVE_ADDR_SHIFT) |
GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);
I915_WRITE_FW(GMBUS3, val);
I915_WRITE_FW(GMBUS1,
GMBUS_CYCLE_WAIT |
(chunk_size << GMBUS_BYTE_COUNT_SHIFT) |
(addr << GMBUS_SLAVE_ADDR_SHIFT) |
GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);
while (len) {
int ret;

Expand All @@ -399,10 +390,9 @@ gmbus_xfer_write_chunk(struct drm_i915_private *dev_priv,
val |= *buf++ << (8 * loop);
} while (--len && ++loop < 4);

I915_WRITE(GMBUS3, val);
I915_WRITE_FW(GMBUS3, val);

ret = gmbus_wait_hw_status(dev_priv, GMBUS_HW_RDY,
GMBUS_HW_RDY_EN);
ret = gmbus_wait(dev_priv, GMBUS_HW_RDY, GMBUS_HW_RDY_EN);
if (ret)
return ret;
}
Expand Down Expand Up @@ -460,13 +450,13 @@ gmbus_xfer_index_read(struct drm_i915_private *dev_priv, struct i2c_msg *msgs)

/* GMBUS5 holds 16-bit index */
if (gmbus5)
I915_WRITE(GMBUS5, gmbus5);
I915_WRITE_FW(GMBUS5, gmbus5);

ret = gmbus_xfer_read(dev_priv, &msgs[1], gmbus1_index);

/* Clear GMBUS5 after each index transfer */
if (gmbus5)
I915_WRITE(GMBUS5, 0);
I915_WRITE_FW(GMBUS5, 0);

return ret;
}
Expand All @@ -478,11 +468,15 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
struct intel_gmbus,
adapter);
struct drm_i915_private *dev_priv = bus->dev_priv;
const unsigned int fw =
intel_uncore_forcewake_for_reg(dev_priv, GMBUS0,
FW_REG_READ | FW_REG_WRITE);
int i = 0, inc, try = 0;
int ret = 0;

intel_uncore_forcewake_get(dev_priv, fw);
retry:
I915_WRITE(GMBUS0, bus->reg0);
I915_WRITE_FW(GMBUS0, bus->reg0);

for (; i < num; i += inc) {
inc = 1;
Expand All @@ -496,8 +490,8 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
}

if (!ret)
ret = gmbus_wait_hw_status(dev_priv, GMBUS_HW_WAIT_PHASE,
GMBUS_HW_WAIT_EN);
ret = gmbus_wait(dev_priv,
GMBUS_HW_WAIT_PHASE, GMBUS_HW_WAIT_EN);
if (ret == -ETIMEDOUT)
goto timeout;
else if (ret)
Expand All @@ -508,7 +502,7 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
* a STOP on the very first cycle. To simplify the code we
* unconditionally generate the STOP condition with an additional gmbus
* cycle. */
I915_WRITE(GMBUS1, GMBUS_CYCLE_STOP | GMBUS_SW_RDY);
I915_WRITE_FW(GMBUS1, GMBUS_CYCLE_STOP | GMBUS_SW_RDY);

/* Mark the GMBUS interface as disabled after waiting for idle.
* We will re-enable it at the start of the next xfer,
Expand All @@ -519,7 +513,7 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
adapter->name);
ret = -ETIMEDOUT;
}
I915_WRITE(GMBUS0, 0);
I915_WRITE_FW(GMBUS0, 0);
ret = ret ?: i;
goto out;

Expand Down Expand Up @@ -548,9 +542,9 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
* of resetting the GMBUS controller and so clearing the
* BUS_ERROR raised by the slave's NAK.
*/
I915_WRITE(GMBUS1, GMBUS_SW_CLR_INT);
I915_WRITE(GMBUS1, 0);
I915_WRITE(GMBUS0, 0);
I915_WRITE_FW(GMBUS1, GMBUS_SW_CLR_INT);
I915_WRITE_FW(GMBUS1, 0);
I915_WRITE_FW(GMBUS0, 0);

DRM_DEBUG_KMS("GMBUS [%s] NAK for addr: %04x %c(%d)\n",
adapter->name, msgs[i].addr,
Expand All @@ -573,7 +567,7 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
timeout:
DRM_DEBUG_KMS("GMBUS [%s] timed out, falling back to bit banging on pin %d\n",
bus->adapter.name, bus->reg0 & 0xff);
I915_WRITE(GMBUS0, 0);
I915_WRITE_FW(GMBUS0, 0);

/*
* Hardware may not support GMBUS over these pins? Try GPIO bitbanging
Expand All @@ -582,6 +576,7 @@ do_gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
ret = -EAGAIN;

out:
intel_uncore_forcewake_put(dev_priv, fw);
return ret;
}

Expand Down

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