From: Ville Syrjälä <[email protected]> When the GMBUS based i2c transfer times out, we try to fall back to bit-banging and retry the operation that way. However if the bit-banging attempt also fails, we should probably go back to the GMBUS method for the next attempt. Maybe there simply wasn't anyone one the bus at this time.
There's also a bit of a mess going on with the force_bit handling. It's supposed to be a ref count actually, and it is as far as intel_gmbus_force_bit() is concerned. But it's treated as just a flag by the timeout based bit-banging fallback. I suppose that's fine since we should never end up in the timeout fallback case if force_bit was already non-zero. However now that we want to restore things back to where they were after the bit-banging attempt failed, we're going to have to do things a bit differently to avoid clobbering the force_bit count as set up by intel_gmbus_force_bit(). So let's dedicate the high bit as a flag for the low level timeout based fallback and treat the rest of the bits as a ref count just as before. Signed-off-by: Ville Syrjälä <[email protected]> --- drivers/gpu/drm/i915/i915_drv.h | 1 + drivers/gpu/drm/i915/intel_i2c.c | 10 +++++++--- 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index f37ac120a29d..2348fea59592 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -1043,6 +1043,7 @@ struct intel_fbc_work; struct intel_gmbus { struct i2c_adapter adapter; +#define GMBUS_FORCE_BIT_RETRY (1U << 31) u32 force_bit; u32 reg0; i915_reg_t gpio_reg; diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 7bf8a485e18f..5d4b3604afd2 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -579,7 +579,6 @@ timeout: * Hardware may not support GMBUS over these pins? Try GPIO bitbanging * instead. Use EAGAIN to have i2c core retry. */ - bus->force_bit = 1; ret = -EAGAIN; out: @@ -597,10 +596,15 @@ gmbus_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num) intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS); mutex_lock(&dev_priv->gmbus_mutex); - if (bus->force_bit) + if (bus->force_bit) { ret = i2c_bit_algo.master_xfer(adapter, msgs, num); - else + if (ret < 0) + bus->force_bit &= ~GMBUS_FORCE_BIT_RETRY; + } else { ret = do_gmbus_xfer(adapter, msgs, num); + if (ret == -EAGAIN) + bus->force_bit |= GMBUS_FORCE_BIT_RETRY; + } mutex_unlock(&dev_priv->gmbus_mutex); intel_display_power_put(dev_priv, POWER_DOMAIN_GMBUS); -- 2.4.10 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
