Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758780AbcLPVJn (ORCPT ); Fri, 16 Dec 2016 16:09:43 -0500 Received: from mail.savoirfairelinux.com ([208.88.110.44]:52198 "EHLO mail.savoirfairelinux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758293AbcLPVJc (ORCPT ); Fri, 16 Dec 2016 16:09:32 -0500 From: Vivien Didelot To: Peter Rosin Cc: Wolfram Sang , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@savoirfairelinux.com, Vivien Didelot Subject: [PATCH] i2c: i2c-mux-pca954x: only reset last channel on error Date: Fri, 16 Dec 2016 16:08:43 -0500 Message-Id: <20161216210843.26853-1-vivien.didelot@savoirfairelinux.com> X-Mailer: git-send-email 2.10.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1242 Lines: 31 The current code is selecting the mux channel before each operation and does not benefit from the cached value (data->last_chan). That is because pca954x_select_chan() considers any non-zero values from pca954x_reg_write() as an error. But this function (via __i2c_transfer) returns either a negative error code or the positive number of messages executed. Only check "ret" against negative values to restore the caching. Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure") Signed-off-by: Vivien Didelot --- drivers/i2c/muxes/i2c-mux-pca954x.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index 8bc3d36..0469f1e 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -179,7 +179,7 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan) /* Only select the channel if its different from the last channel */ if (data->last_chan != regval) { ret = pca954x_reg_write(muxc->parent, client, regval); - data->last_chan = ret ? 0 : regval; + data->last_chan = ret < 0 ? 0 : regval; } return ret; -- 2.10.2