On Wed, Mar 28, 2012 at 3:02 AM, Chris Wilson <chris at chris-wilson.co.uk>
wrote:
> On Wed, 28 Mar 2012 02:36:22 +0800, Daniel Kurtz <djkurtz at chromium.org>
> wrote:
>> Save the GMBUS2 value read while polling for state changes, and then
>> reuse this value when determining for which reason the loops were exited.
>> This is a small optimization which saves a couple of bus accesses for
>> memory mapped IO registers.
>>
>> To avoid "assigning in if clause" checkpatch errors", use a ret variable
>> to store the wait_for macro return value.
>>
>> Signed-off-by: Daniel Kurtz <djkurtz at chromium.org>
>> ---
>> ?drivers/gpu/drm/i915/intel_i2c.c | ? 32 ++++++++++++++++++++------------
>> ?1 files changed, 20 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_i2c.c
>> b/drivers/gpu/drm/i915/intel_i2c.c
>> index c71f3dc..174fc71 100644
>> --- a/drivers/gpu/drm/i915/intel_i2c.c
>> +++ b/drivers/gpu/drm/i915/intel_i2c.c
>> @@ -210,6 +210,7 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv,
>> struct i2c_msg *msg,
>> ? ? ? int reg_offset = dev_priv->gpio_mmio_base;
>> ? ? ? u16 len = msg->len;
>> ? ? ? u8 *buf = msg->buf;
>> + ? ? u32 gmbus2;
> Does the temporary really need such broad scoping?
>
>> ? ? ? I915_WRITE(GMBUS1 + reg_offset,
>> ? ? ? ? ? ? ? ? ?gmbus1 |
>> @@ -219,13 +220,15 @@ gmbus_xfer_read(struct drm_i915_private *dev_priv,
>> struct i2c_msg *msg,
>> ? ? ? ? ? ? ? ? ?GMBUS_SLAVE_READ | GMBUS_SW_RDY);
>> ? ? ? POSTING_READ(GMBUS2 + reg_offset);
> Might as well shave this read as well.
Do you know why POSTING_READ() was there in the first place?
As far as I can tell, these are used to ensure memory barriers are
inserted between a group of writes, and subsequent reads to memory
mapped io registers.
However, the normal I915_READ() and I915_WRITE() macros already call
readl() / writel(), which already have an explicit mb().
So, can we just get rid of all of them, or am I missing something?
If so, I propose we do that in another patch, and leave this one alone.
>
>> ? ? ? do {
>> + ? ? ? ? ? ? int ret;
>> ? ? ? ? ? ? ? u32 val, loop = 0;
>>
>> - ? ? ? ? ? ? if (wait_for(I915_READ(GMBUS2 + reg_offset) &
>> - ? ? ? ? ? ? ? ? ? ? ? ? ?(GMBUS_SATOER | GMBUS_HW_RDY),
>> - ? ? ? ? ? ? ? ? ? ? ? ? ?50))
>> + ? ? ? ? ? ? ret = wait_for((gmbus2 = I915_READ(GMBUS2 + reg_offset)) &
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ?(GMBUS_SATOER | GMBUS_HW_RDY),
>> + ? ? ? ? ? ? ? ? ? ? ? ? ? ?50);
>> + ? ? ? ? ? ? if (ret)
>> ? ? ? ? ? ? ? ? ? ? ? return -ETIMEDOUT;
>> - ? ? ? ? ? ? if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER)
>> + ? ? ? ? ? ? if (gmbus2 & GMBUS_SATOER)
>> ? ? ? ? ? ? ? ? ? ? ? return -ENXIO;
>>
>> ? ? ? ? ? ? ? val = I915_READ(GMBUS3 + reg_offset);
>> @@ -245,6 +248,7 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv,
>> struct i2c_msg *msg)
>> ? ? ? u16 len = msg->len;
>> ? ? ? u8 *buf = msg->buf;
>> ? ? ? u32 val, loop;
>> + ? ? u32 gmbus2;
>>
>> ? ? ? val = loop = 0;
>> ? ? ? while (len && loop < 4) {
>> @@ -260,6 +264,7 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv,
>> struct i2c_msg *msg)
>> ? ? ? ? ? ? ? ? ?GMBUS_SLAVE_WRITE | GMBUS_SW_RDY);
>> ? ? ? POSTING_READ(GMBUS2 + reg_offset);
>> ? ? ? while (len) {
>> + ? ? ? ? ? ? int ret;
>> ? ? ? ? ? ? ? val = loop = 0;
>> ? ? ? ? ? ? ? do {
>> ? ? ? ? ? ? ? ? ? ? ? val |= *buf++ << (8 * loop);
>> @@ -268,11 +273,12 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv,
>> struct i2c_msg *msg)
>> ? ? ? ? ? ? ? I915_WRITE(GMBUS3 + reg_offset, val);
>> ? ? ? ? ? ? ? POSTING_READ(GMBUS2 + reg_offset);
>
> And here.
>
> --
> Chris Wilson, Intel Open Source Technology Centre
