linux-kernel - Re: [PATCH v5] i2c: omap: correct usage of the interrupt enable register

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Date:	Wed, 19 Jun 2013 12:05:09 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Oleksandr Dmytryshyn <oleksandr.dmytryshyn@...com>
Cc:	Tony Lindgren <tony@...mide.com>, linux-omap@...r.kernel.org,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5] i2c: omap: correct usage of the interrupt enable
 register

On Mon, Jun 03, 2013 at 10:37:20AM +0300, Oleksandr Dmytryshyn wrote:
> We've been lucky not to have any interrupts fire during the suspend
> path, otherwise we would have unpredictable behaviour in the kernel.
> 
> Based on the logic of the kernel code interrupts from i2c should be
> prohibited during suspend. Kernel writes 0 to the I2C_IE register in
> the omap_i2c_runtime_suspend() function. In the other side kernel
> writes saved interrupt flags to the I2C_IE register in
> omap_i2c_runtime_resume() function. I.e. interrupts should be disabled
> during suspend.
> 
> This works for chips with version1 registers scheme. Interrupts are
> disabled during suspend. For chips with version2 scheme registers
> writting 0 to the I2C_IE register does nothing (because now the
> I2C_IRQENABLE_SET register is located at this address). This register
> is used to enable interrupts. For disabling interrupts
> I2C_IRQENABLE_CLR register should be used.
> 
> Because the registers I2C_IRQENABLE_SET and I2C_IE have the same
> addresses, the interrupt enabling procedure is unchanged.
> 
> I've checked that interrupts in the i2c controller are still enabled
> after writting 0 to the I2C_IRQENABLE_SET register. With this patch
> interrupts are disabled in the omap_i2c_runtime_suspend() function.
> 
> Patch is based on:
> git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> tag: v3.10-rc2

Last paragraph should be below "---".

> 
> Verified on OMAP4430.
> 
> Signed-off-by: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@...com>

Applied to for-next, thanks!


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