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[2/3] drm/i915: Don't try indexed reads to alternate slave addresses

Message ID 20171123194157.25367-2-ville.syrjala@linux.intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Ville Syrjälä Nov. 23, 2017, 7:41 p.m. UTC 
From: Ville Syrjälä <ville.syrjala@linux.intel.com>

We can only specify the one slave address to indexed reads/writes.
Make sure the messages we check are destined to the same slave
address before deciding to do an indexed transfer.

Cc: stable@vger.kernel.org
Cc: Daniel Kurtz <djkurtz@chromium.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Sean Paul <seanpaul@chromium.org>
Fixes: 56f9eac05489 ("drm/i915/intel_i2c: use INDEX cycles for i2c read transactions")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/i915/intel_i2c.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Chris Wilson Nov. 23, 2017, 8:52 p.m. UTC | #1 
Quoting Ville Syrjala (2017-11-23 19:41:56)
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> We can only specify the one slave address to indexed reads/writes.
> Make sure the messages we check are destined to the same slave
> address before deciding to do an indexed transfer.
> 
> Cc: stable@vger.kernel.org
> Cc: Daniel Kurtz <djkurtz@chromium.org>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Sean Paul <seanpaul@chromium.org>
> Fixes: 56f9eac05489 ("drm/i915/intel_i2c: use INDEX cycles for i2c read transactions")
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris
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Patch

diff --git a/drivers/gpu/drm/i915/intel_i2c.c b/drivers/gpu/drm/i915/intel_i2c.c
index 165375cbef2f..4b4528d7010f 100644
--- a/drivers/gpu/drm/i915/intel_i2c.c
+++ b/drivers/gpu/drm/i915/intel_i2c.c
@@ -438,6 +438,7 @@  static bool
 gmbus_is_index_read(struct i2c_msg *msgs, int i, int num)
 {
 	return (i + 1 < num &&
+		msgs[i].addr == msgs[i + 1].addr &&
 		!(msgs[i].flags & I2C_M_RD) && msgs[i].len <= 2 &&
 		(msgs[i + 1].flags & I2C_M_RD));
 }