Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754809AbcCRIsc (ORCPT ); Fri, 18 Mar 2016 04:48:32 -0400 Received: from mail-wm0-f65.google.com ([74.125.82.65]:36575 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753750AbcCRIrA (ORCPT ); Fri, 18 Mar 2016 04:47:00 -0400 From: Jan Glauber To: Wolfram Sang Cc: linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org, David Daney , Peter Swain , Jan Glauber Subject: [PATCH v4 09/14] i2c-octeon: Faster operation when IFLG signals late Date: Fri, 18 Mar 2016 09:46:34 +0100 Message-Id: X-Mailer: git-send-email 1.9.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2064 Lines: 64 From: Peter Swain Some versions can deliver low-level twsi irq before twsi_ctl.iflg is set, leading to timeout-driven i/o. When an irq signals event, but woken task does not see the expected twsi_ctl.iflg, re-check about 80uS later. EEPROM reads on 100kHz i2c now measure ~5.2kB/s, about 1/2 what's achievable, and much better than the worst-case 100 bytes/sec before. Signed-off-by: Peter Swain Signed-off-by: Jan Glauber Acked-by: David Daney --- drivers/i2c/busses/i2c-octeon.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/drivers/i2c/busses/i2c-octeon.c b/drivers/i2c/busses/i2c-octeon.c index aa676ce..d3a3e2e 100644 --- a/drivers/i2c/busses/i2c-octeon.c +++ b/drivers/i2c/busses/i2c-octeon.c @@ -342,6 +342,28 @@ static int octeon_i2c_test_iflg(struct octeon_i2c *i2c) return (octeon_i2c_read_ctl(i2c) & TWSI_CTL_IFLG) != 0; } +#define I2C_OCTEON_IFLG_WAIT 80 /* microseconds */ + +/* + * Wait-helper which addresses the delayed-IFLAG problem by re-polling for + * missing TWSI_CTL[IFLG] a few us later, when irq has signalled an event, + * but none found. Skip this re-poll on the first (non-wakeup) call. + */ +static int poll_iflg(struct octeon_i2c *i2c, int *first_p) +{ + int iflg = octeon_i2c_test_iflg(i2c); + + if (iflg) + return 1; + if (*first_p) + *first_p = 0; + else { + usleep_range(I2C_OCTEON_IFLG_WAIT, 2 * I2C_OCTEON_IFLG_WAIT); + iflg = octeon_i2c_test_iflg(i2c); + } + return iflg; +} + /** * octeon_i2c_wait - wait for the IFLG to be set * @i2c: The struct octeon_i2c @@ -351,9 +373,10 @@ static int octeon_i2c_test_iflg(struct octeon_i2c *i2c) static int octeon_i2c_wait(struct octeon_i2c *i2c) { long time_left; + int first = 1; i2c->int_en(i2c); - time_left = wait_event_timeout(i2c->queue, octeon_i2c_test_iflg(i2c), + time_left = wait_event_timeout(i2c->queue, poll_iflg(i2c, &first), i2c->adap.timeout); i2c->int_dis(i2c); if (!time_left) { -- 1.9.1