linux-kernel - Re: [PATCH v3 1/1] i2c: omap: correct usage of the interrupt enable register

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Date:	Fri, 31 May 2013 07:06:48 -0500
From:	Dan Murphy <dmurphy@...com>
To:	Oleksandr Dmytryshyn <oleksandr.dmytryshyn@...com>
CC:	Tony Lindgren <tony@...mide.com>, Wolfram Sang <wsa@...-dreams.de>,
	<linux-omap@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/1] i2c: omap: correct usage of the interrupt enable
 register

On 05/31/2013 03:26 AM, Oleksandr Dmytryshyn wrote:
> If the i2c controller during suspend will generate an interrupt, it
> can lead to 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.
>
> Change-Id: Ie49165990a4e7c67a4ccf2e4a66cd3b78f2e2b70
Remove this.
> Signed-off-by: Oleksandr Dmytryshyn <oleksandr.dmytryshyn@...com>
> ---
>  drivers/i2c/busses/i2c-omap.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
> index e02f9e3..64c26f9 100644
> --- a/drivers/i2c/busses/i2c-omap.c
> +++ b/drivers/i2c/busses/i2c-omap.c
> @@ -180,6 +180,8 @@ enum {
>  #define I2C_OMAP_ERRATA_I207		(1 << 0)
>  #define I2C_OMAP_ERRATA_I462		(1 << 1)
>  
> +#define OMAP_I2C_IP_V2_INTERRUPTS_MASK	0x6FFF
> +
>  struct omap_i2c_dev {
>  	spinlock_t		lock;		/* IRQ synchronization */
>  	struct device		*dev;
> @@ -193,6 +195,7 @@ struct omap_i2c_dev {
>  						    long latency);
>  	u32			speed;		/* Speed of bus in kHz */
>  	u32			flags;
> +	u16			scheme;
>  	u16			cmd_err;
>  	u8			*buf;
>  	u8			*regs;
> @@ -1082,7 +1085,7 @@ omap_i2c_probe(struct platform_device *pdev)
>  	int irq;
>  	int r;
>  	u32 rev;
> -	u16 minor, major, scheme;
> +	u16 minor, major;
>  
>  	/* NOTE: driver uses the static register mapping */
>  	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> @@ -1159,8 +1162,8 @@ omap_i2c_probe(struct platform_device *pdev)
>  	 */
>  	rev = __raw_readw(dev->base + 0x04);
>  
> -	scheme = OMAP_I2C_SCHEME(rev);
> -	switch (scheme) {
> +	dev->scheme = OMAP_I2C_SCHEME(rev);
> +	switch (dev->scheme) {
>  	case OMAP_I2C_SCHEME_0:
>  		dev->regs = (u8 *)reg_map_ip_v1;
>  		dev->rev = omap_i2c_read_reg(dev, OMAP_I2C_REV_REG);
> @@ -1289,7 +1292,11 @@ static int omap_i2c_runtime_suspend(struct device *dev)
>  
>  	_dev->iestate = omap_i2c_read_reg(_dev, OMAP_I2C_IE_REG);
>  
> -	omap_i2c_write_reg(_dev, OMAP_I2C_IE_REG, 0);
> +	if (_dev->scheme == OMAP_I2C_SCHEME_0)
> +		omap_i2c_write_reg(_dev, OMAP_I2C_IE_REG, 0);
> +	else
> +		omap_i2c_write_reg(_dev, OMAP_I2C_IP_V2_IRQENABLE_CLR,
> +				   OMAP_I2C_IP_V2_INTERRUPTS_MASK);
>  
>  	if (_dev->rev < OMAP_I2C_OMAP1_REV_2) {
>  		omap_i2c_read_reg(_dev, OMAP_I2C_IV_REG); /* Read clears */


-- 
------------------
Dan Murphy

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