From: Daniel Kurtz Date: Fri, 30 Mar 2012 11:46:37 +0000 (+0800) Subject: drm/i915/intel_i2c: use double-buffered writes X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=7a39a9d4767e8d22d60f2c4bf5eece4f4398c274;p=linux-beck.git drm/i915/intel_i2c: use double-buffered writes The GMBUS controller GMBUS3 register is double-buffered. Take advantage of this by writing two 4-byte words before the first wait for HW_RDY. This helps keep the GMBUS controller from becoming idle during long writes. In fact, during experiments using the GMBUS interrupts, the HW_RDY interrupt would only trigger for transactions >4 bytes after 2 writes to GMBUS3. Signed-off-by: Daniel Kurtz Reviewed-by: Chris Wilson Signed-off-by: Daniel Vetter --- diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c index 99a04f8bcb1f..f02e52aca746 100644 --- a/drivers/gpu/drm/i915/intel_i2c.c +++ b/drivers/gpu/drm/i915/intel_i2c.c @@ -262,13 +262,6 @@ 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) { - if (wait_for(I915_READ(GMBUS2 + reg_offset) & - (GMBUS_SATOER | GMBUS_HW_RDY), - 50)) - return -ETIMEDOUT; - if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER) - return -ENXIO; - val = loop = 0; do { val |= *buf++ << (8 * loop); @@ -276,6 +269,13 @@ gmbus_xfer_write(struct drm_i915_private *dev_priv, struct i2c_msg *msg, I915_WRITE(GMBUS3 + reg_offset, val); POSTING_READ(GMBUS2 + reg_offset); + + if (wait_for(I915_READ(GMBUS2 + reg_offset) & + (GMBUS_SATOER | GMBUS_HW_RDY), + 50)) + return -ETIMEDOUT; + if (I915_READ(GMBUS2 + reg_offset) & GMBUS_SATOER) + return -ENXIO; } return 0; }