Date: Thu, 4 Dec 2014 10:42:10 -0800
From: "David E. Box" <david.e.box@linux.intel.com>
To: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Cc: wsa@the-dreams.de, jdelvare@suse.de, arnd@arndb.de,
        maxime.ripard@free-electrons.com, dianders@chromium.org,
        u.kleine-koenig@pengutronix.de,
        laurent.pinchart+renesas@ideasonboard.com,
        boris.brezillon@free-electrons.com, andrew@lunn.ch, sjg@chromium.org,
        markus.mayer@linaro.org, jacob.jun.pan@linux.intel.com,
        max.schwarz@online.de, mika.westerberg@linux.intel.com,
        skuribay@pobox.com, Romain.Baeriswyl@abilis.com, wenkai.du@intel.com,
        chiau.ee.chew@intel.com, alan@linux.intel.com,
        linux-kernel@vger.kernel.org, linux-i2c@vger.kernel.org
Subject: Re: [PATCH V3 1/2] i2c-designware: Add i2c bus locking support
Message-ID: <20141204184210.GA1530@pathfinder>
References: <1411497626-7984-1-git-send-email-david.e.box@linux.intel.com>
 <1417478973-25522-1-git-send-email-david.e.box@linux.intel.com>
 <1417478973-25522-2-git-send-email-david.e.box@linux.intel.com>
 <5480144F.2040506@linux.intel.com>
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On Thu, Dec 04, 2014 at 09:59:11AM +0200, Jarkko Nikula wrote:
> Hi
> 
> On 12/02/2014 02:09 AM, David E. Box wrote:
> >Adds support for acquiring and releasing a hardware bus lock in the i2c
> >designware core transfer function. This is needed for i2c bus controllers
> >that are shared with but not controlled by the kernel.
> >
> >Signed-off-by: David E. Box <david.e.box@linux.intel.com>
> >---
> >  drivers/i2c/busses/i2c-designware-core.c    | 11 +++++++++++
> >  drivers/i2c/busses/i2c-designware-core.h    |  6 ++++++
> >  drivers/i2c/busses/i2c-designware-platdrv.c | 18 +++++++++++++-----
> >  3 files changed, 30 insertions(+), 5 deletions(-)
> >
> ...
> >diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
> >index a743115..afdff3b 100644
> >--- a/drivers/i2c/busses/i2c-designware-platdrv.c
> >+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
> >@@ -261,10 +261,16 @@ static int dw_i2c_probe(struct platform_device *pdev)
> >  		return r;
> >  	}
> >-	pm_runtime_set_autosuspend_delay(&pdev->dev, 1000);
> >-	pm_runtime_use_autosuspend(&pdev->dev);
> >-	pm_runtime_set_active(&pdev->dev);
> >-	pm_runtime_enable(&pdev->dev);
> >+	i2c_dw_eval_lock_support(dev);
> i2c_dw_eval_lock_support() is added in the next patch.
> >+
> >+	if (dev->pm_runtime_disabled) {
> >+		pm_runtime_forbid(&pdev->dev);
> >+	} else {
> >+		pm_runtime_set_autosuspend_delay(&pdev->dev, 1000);
> >+		pm_runtime_use_autosuspend(&pdev);
> >+		pm_runtime_set_active(&pdev->dev);
> >+		pm_runtime_enable(&pdev->dev);
> >+	}
> >  	return 0;
> >  }
> >@@ -314,7 +320,9 @@ static int dw_i2c_resume(struct device *dev)
> >  	struct dw_i2c_dev *i_dev = platform_get_drvdata(pdev);
> >  	clk_prepare_enable(i_dev->clk);
> >-	i2c_dw_init(i_dev);
> >+
> >+	if (!i_dev->pm_runtime_disabled)
> >+		i2c_dw_init(i_dev);
> Should there be similar conditional call or locking around
> i2c_dw_init() and i2c_dw_disable_int() also in dw_i2c_probe()?
> 

Timely reply. Around i2c_dw_init(), yes. I just discovered this as the source
of a recent hang that's occuring in the loop in __i2c_dw_enable().
The hange occurs very infrequently and only, so far, when not built in. A
block around i2c_dw_disable_int() would make sense as well as a precaution.

Dave
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