linux-kernel - Re: [PATCH V2] i2c-designware: Mask all interrupts during i2c controller enable

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Date:	Wed, 14 May 2014 17:53:41 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	"Du, Wenkai" <wenkai.du@...el.com>
Cc:	"'linux-i2c@...r.kernel.org'" <linux-i2c@...r.kernel.org>,
	"Westerberg, Mika" <mika.westerberg@...el.com>,
	"'linux-kernel@...r.kernel.org'" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2] i2c-designware: Mask all interrupts during i2c
 controller enable

On Thu, Apr 10, 2014 at 11:03:19PM +0000, Du, Wenkai wrote:
> Hi all,
> 
> Updated problem descriptions from Mika's feedback and new test data: 
> 
> There have been "i2c_designware 80860F41:00: controller timed out" errors
> on a number of Baytrail platforms. The issue is caused by incorrect value in
> Interrupt Mask Register (DW_IC_INTR_MASK)  when i2c core is being enabled. 
> This causes call to __i2c_dw_enable() to immediately start the transfer which
> leads to timeout. There are 3 failure modes observed:
> 
> 1. Failure in S0 to S3 resume path
> 
> The default value after reset for DW_IC_INTR_MASK is 0x8ff. When we start 
> the first transaction after resuming from system sleep, TX_EMPTY interrupt 
> is already unmasked because of the hardware default.
> 
> 2. Failure in normal operational path
> 
> This failure happens rarely and is hard to reproduce. Debug trace showed that
> DW_IC_INTR_MASK had value of 0x254 when failure occurred, which meant 
> TX_EMPTY was unmasked.
> 
> 2. Failure in S3 to S0 suspend path
> 
> This failure also happens rarely and is hard to reproduce. Adding debug trace
> that read DW_IC_INTR_MASK made this failure not reproducible. But from ISR 
> call trace we could conclude TX_EMPTY was unmasked when problem occurred.
> 
> 
> The patch masks all interrupts before the controller is enabled to resolve the
> faulty DW_IC_INTR_MASK conditions.
> 
> Signed-off-by: Wenkai Du <wenkai.du@...el.com>

Fixed the commit message and improved the comment to:
	/* enforce disabled interrupts (due to HW issues) */"

Applied to for-current, thanks!


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