[PATCH v4 4/5] ARM: mediatek: Add EINT support to MTK pinctrl driver.

[Yingjoe Chen]

On Thu, 2015-01-15 at 18:30 +0100, Linus Walleij wrote:
> On Wed, Jan 14, 2015 at 3:32 AM, Yingjoe Chen <yingjoe.chen at mediatek.com> wrote:
> 
> > Let's me describe my problem more clearly. On our SoC, if a pin support
> > interrupt it will have 2 different numbers for it. For examples, here's
> > a partial list for the gpio and EINT number mappings on mt8135:
> >
> >    gpio  EINT
> >      0     49
> >      1     48
> >     ...........
> >     36     97
> >     37     19
> >     ...........
> >
> > To control interrupt related function, we'll need EINT number to locate
> > corresponding register bits. When interrupt occurs, the interrupt
> > handler will know which EINT interrupt occurs. In irq_chip functions,
> > only .irq_request_resources and .irq_release_resources use gpio number
> > to set pinmux to EINT mode and all the others need EINT number.
> >
> > Because EINT number is used more frequently in interrupt related
> > functions, it make sense to use EINT number as hwirq instead of gpio
> > number. That means irq_domain will translate EINT number to virq.
> > So what mtk_gpio_to_irq actually do is translate gpio number to EINT
> > number and use irq domain to translate it to virq.
> 
> But the EINT is not a hardware number is it?

It is a hardware number. eg, to mask irq for the gpio 0 above, we have
to set bit49 in EINT mask_set register. When this irq triggered, it is
reported using EINT status register bit49.

We can find out EINT number for a GPIO using mtk_desc_pin tables. In
drivers/pinctrl/mediatek/pinctrl-mtk-mt8135.h, for GPIO0, we can see its
EINT is 49 and must set to function 2 for EINT. I believe this is
similar to sunxi.

        MTK_PIN(
                PINCTRL_PIN(0, "MSDC0_DAT7"),
                "D21", "mt8135",
                MTK_EINT_FUNCTION(2, 49),
                MTK_FUNCTION(0, "GPIO0"),
                MTK_FUNCTION(1, "MSDC0_DAT7"),
                MTK_FUNCTION(2, "EINT49"),
                MTK_FUNCTION(3, "I2SOUT_DAT"),
                MTK_FUNCTION(4, "DAC_DAT_OUT"),
                MTK_FUNCTION(5, "PCM1_DO"),
                MTK_FUNCTION(6, "SPI1_MO"),
                MTK_FUNCTION(7, "NALE")
        ),

Joe.C