From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f47.google.com ([74.125.82.47]:37800 "EHLO mail-wm0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753837AbcKBOhS (ORCPT ); Wed, 2 Nov 2016 10:37:18 -0400 Received: by mail-wm0-f47.google.com with SMTP id t79so41497032wmt.0 for ; Wed, 02 Nov 2016 07:37:18 -0700 (PDT) Date: Wed, 2 Nov 2016 14:39:58 +0000 From: Lee Jones To: Linus Walleij Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Patrice Chotard , Amelie Delaunay Subject: Re: [PATCH] mfd: stmpe: Fix RESET regression on STMPE2401 Message-ID: <20161102143958.GW13127@dell> References: <1477992173-30964-1-git-send-email-linus.walleij@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1477992173-30964-1-git-send-email-linus.walleij@linaro.org> Sender: stable-owner@vger.kernel.org List-ID: On Tue, 01 Nov 2016, Linus Walleij wrote: > Since commit c4dd1ba355aae2bc3d1213da6c66c53e3c31e028 > ("mfd: stmpe: Add reset support for all STMPE variant") > we're resetting the STMPE expanders before use. > > This caused a regression on the STMP2401 on the Nomadik > NHK8815: > > stmpe-i2c 0-0043: stmpe2401 detected, chip id: 0x101 > nmk-i2c 101f8000.i2c0: write to slave 0x43 timed out > nmk-i2c 101f8000.i2c0: no ack received after address transmission > stmpe-i2c 0-0044: stmpe2401 detected, chip id: 0x101 > nmk-i2c 101f8000.i2c0: write to slave 0x44 timed out > nmk-i2c 101f8000.i2c0: no ack received after address transmission > > It turns out that we start to poll for the reset bit to > go low again too quickly: the STMPE2401 is not yet online and > ready to be asked for the status of the RESET bit. > > By introducing a 10ms delay before starting to hammer > the register for information, we get back to normal: > > stmpe-i2c 0-0043: stmpe2401 detected, chip id: 0x101 > stmpe-i2c 0-0044: stmpe2401 detected, chip id: 0x101 > > Cc: stable@vger.kernel.org > Cc: Patrice Chotard > Cc: Amelie Delaunay > Cc: Lee Jones > Fixes: c4dd1ba355aa ("mfd: stmpe: Add reset support for all STMPE variant") > Signed-off-by: Linus Walleij > --- > drivers/mfd/stmpe.c | 2 ++ > 1 file changed, 2 insertions(+) Applied to -fixes. > diff --git a/drivers/mfd/stmpe.c b/drivers/mfd/stmpe.c > index cfdae8a3d779..b0c7bcdaf5df 100644 > --- a/drivers/mfd/stmpe.c > +++ b/drivers/mfd/stmpe.c > @@ -851,6 +851,8 @@ static int stmpe_reset(struct stmpe *stmpe) > if (ret < 0) > return ret; > > + msleep(10); > + > timeout = jiffies + msecs_to_jiffies(100); > while (time_before(jiffies, timeout)) { > ret = __stmpe_reg_read(stmpe, stmpe->regs[STMPE_IDX_SYS_CTRL]); -- Lee Jones Linaro STMicroelectronics Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog