On Feb 15, 2012 6:48 PM, "Daniel Vetter" <daniel@xxxxxxxx> wrote: > > On Thu, Feb 09, 2012 at 12:03:17PM -0800, Benson Leung wrote: > > gmbus_xfer with a single message (particularly a single message write) would > > set Bus Cycle Select to 100b, the Gen Stop cycle, instead of 101b, > > No Index, Stop cycle. This would not start single message i2c transactions. > > > > Also, gmbus_xfer done: will disable the interface without checking if > > it is idle. In the case of writes, there will be no wait on status or delay > > to ensure the write starts and completes before the interface is turned off. > > > > Fixed the former issue by using the same cycle selection as used in the > > I2C_M_RD for the write case. > > GMBUS_CYCLE_WAIT | (i + 1 == num ? GMBUS_CYCLE_STOP : 0) > > Fixed the latter by waiting on GMBUS_ACTIVE to deassert before disable. > > > > Signed-off-by: Benson Leung <bleung@xxxxxxxxxxxx> Reviewed-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx> > > Can you clarify the commit message a bit and say that the first hunk is > just for optics and the issue is only with the write path (because the > read path is correct already). Silly me is just to easily confused ;-) > > Btw, I've reworked the gmbus -> gpio bit-banging fallback code a bit and > if that passes review and all I'll reenable gmbus by default again. See > > http://cgit.freedesktop.org/~danvet/drm/log/?h=gmbus If the write case is fixed by Benson's patch, is there any known use case that still requires i2c bit banging on these pins? It would be a nice cleanup to remove it completely. Also, I can think of at least two further potential performance improvements that I was wondering if anybody has yet pursued: (1) Enabling the i915's gmbus interrupt. This would eliminate the need for the (relatively slow) wait_for polling loop. (2) Taking advantage of the i915's "INDEX" cycles to combine writing a (1 or 2 byte) address & reading back an array of bytes into a single transaction. Best Regards, -Daniel > > Yours, Daniel > > > --- > > drivers/gpu/drm/i915/intel_i2c.c | 13 +++++++++---- > > 1 files changed, 9 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c > > index d30cccc..64bb9cd 100644 > > --- a/drivers/gpu/drm/i915/intel_i2c.c > > +++ b/drivers/gpu/drm/i915/intel_i2c.c > > @@ -249,7 +249,8 @@ gmbus_xfer(struct i2c_adapter *adapter, > > > > if (msgs[i].flags & I2C_M_RD) { > > I915_WRITE(GMBUS1 + reg_offset, > > - GMBUS_CYCLE_WAIT | (i + 1 == num ? GMBUS_CYCLE_STOP : 0) | > > + GMBUS_CYCLE_WAIT | > > + (i + 1 == num ? GMBUS_CYCLE_STOP : 0) | > > (len << GMBUS_BYTE_COUNT_SHIFT) | > > (msgs[i].addr << GMBUS_SLAVE_ADDR_SHIFT) | > > GMBUS_SLAVE_READ | GMBUS_SW_RDY); > > @@ -278,7 +279,8 @@ gmbus_xfer(struct i2c_adapter *adapter, > > > > I915_WRITE(GMBUS3 + reg_offset, val); > > I915_WRITE(GMBUS1 + reg_offset, > > - (i + 1 == num ? GMBUS_CYCLE_STOP : GMBUS_CYCLE_WAIT) | > > + GMBUS_CYCLE_WAIT | > > + (i + 1 == num ? GMBUS_CYCLE_STOP : 0) | > > (msgs[i].len << GMBUS_BYTE_COUNT_SHIFT) | > > (msgs[i].addr << GMBUS_SLAVE_ADDR_SHIFT) | > > GMBUS_SLAVE_WRITE | GMBUS_SW_RDY); > > @@ -317,9 +319,12 @@ clear_err: > > I915_WRITE(GMBUS1 + reg_offset, 0); > > > > done: > > - /* Mark the GMBUS interface as disabled. We will re-enable it at the > > - * start of the next xfer, till then let it sleep. > > + /* Mark the GMBUS interface as disabled after waiting for idle. > > + * We will re-enable it at the start of the next xfer, > > + * till then let it sleep. > > */ > > + if (wait_for((I915_READ(GMBUS2 + reg_offset) & GMBUS_ACTIVE) == 0, 10)) > > + DRM_INFO("GMBUS timed out waiting for idle\n"); > > I915_WRITE(GMBUS0 + reg_offset, 0); > > return i; > > > > -- > > 1.7.1 > > > > _______________________________________________ > > dri-devel mailing list > > dri-devel@xxxxxxxxxxxxxxxxxxxxx > > http://lists.freedesktop.org/mailman/listinfo/dri-devel > > -- > Daniel Vetter > Mail: daniel@xxxxxxxx > Mobile: +41 (0)79 365 57 48 _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
