linux-kernel - Re: [PATCH v2 3/4] gpio: Add in ast2600 details to Aspeed driver

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Message-ID: <aa7bf455b3ef834fb4e965a6cfc594dc1f7ddb1c.camel@gmail.com>
Date:   Thu, 05 Sep 2019 17:08:24 +1000
From:   Rashmica Gupta <rashmica.g@...il.com>
To:     Andrew Jeffery <andrew@...id.au>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Joel Stanley <joel@....id.au>, linux-gpio@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/4] gpio: Add in ast2600 details to Aspeed driver

On Thu, 2019-09-05 at 13:27 +0930, Andrew Jeffery wrote:
> 
> On Thu, 5 Sep 2019, at 10:47, Rashmica Gupta wrote:
> > The ast2600 is a new generation of SoC from ASPEED. Similarly to
> > the
> > ast2400 and ast2500, it has a GPIO controller for it's 3.6V GPIO
> > pins.
> > Additionally, it has a GPIO controller for 36 1.8V GPIO pins. These
> > voltages are fixed and cannot be configured via pinconf, so we need
> > two
> > separate drivers for them.
> 
> Working backwards, we don't really have multiple drivers, just
> different
> configurations for the same driver. So I think this should be
> reworded.
> 
> Also it's not really the voltage differences that are driving the
> different
> configurations but rather that there are two separate sets of
> registers
> in the 2600 with overlapping bank names (they happen to be split into
> 3.3V and 1.8V groups). The key point being that there aren't just
> more
> GPIO registers tacked on the end of the original 3.3V group.
> 

Good point! I'll reword this. Also they are 3.3V, I'm not sure why I
wrote 3.6V in my patches.

> > Signed-off-by: Rashmica Gupta <rashmica.g@...il.com>
> > ---
> >  drivers/gpio/gpio-aspeed.c | 30 ++++++++++++++++++++++++++++--
> >  1 file changed, 28 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpio/gpio-aspeed.c b/drivers/gpio/gpio-
> > aspeed.c
> > index 16c6eaf70857..4723b8780a8c 100644
> > --- a/drivers/gpio/gpio-aspeed.c
> > +++ b/drivers/gpio/gpio-aspeed.c
> > @@ -662,12 +662,14 @@ static void aspeed_gpio_irq_handler(struct
> > irq_desc *desc)
> >  	struct gpio_chip *gc = irq_desc_get_handler_data(desc);
> >  	struct irq_chip *ic = irq_desc_get_chip(desc);
> >  	struct aspeed_gpio *data = gpiochip_get_data(gc);
> > -	unsigned int i, p, girq;
> > +	unsigned int i, p, girq, banks;
> >  	unsigned long reg;
> > +	struct aspeed_gpio *gpio = gpiochip_get_data(gc);
> >  
> >  	chained_irq_enter(ic, desc);
> >  
> > -	for (i = 0; i < ARRAY_SIZE(aspeed_gpio_banks); i++) {
> > +	banks = DIV_ROUND_UP(gpio->config->nr_gpios, 32);
> > +	for (i = 0; i < banks; i++) {
> >  		const struct aspeed_gpio_bank *bank =
> > &aspeed_gpio_banks[i];
> >  
> >  		reg = ioread32(bank_reg(data, bank, reg_irq_status));
> > @@ -1108,9 +1110,33 @@ static const struct aspeed_gpio_config
> > ast2500_config =
> >  	/* 232 for simplicity, actual number is 228 (4-GPIO hole in
> > GPIOAB) */
> >  	{ .nr_gpios = 232, .props = ast2500_bank_props, };
> >  
> > +static const struct aspeed_bank_props ast2600_bank_props[] = {
> > +	/*     input	  output   */
> > +	{5, 0xffffffff,  0x0000ffff}, /* U/V/W/X */
> > +	{6, 0xffff0000,  0x0fff0000}, /* Y/Z */
> > +	{ },
> > +};
> > +
> > +static const struct aspeed_gpio_config ast2600_config =
> > +	/* 208 3.6V GPIOs */
> > +	{ .nr_gpios = 208, .props = ast2600_bank_props, };
> > +
> > +static const struct aspeed_bank_props ast2600_1_8v_bank_props[] =
> > {
> > +	/*     input	  output   */
> > +	{1, 0x0000000f,  0x0000000f}, /* E */
> 
> If there are 36 GPIOs then this configuration is suggesting that all
> of them
> are capable of input and output. A handy observation here is that the
> first
> 36 GPIOs of the 3.3V GPIO controller in the 2600 also have both
> capabilities,
> so we can re-use the 3.3V configuration if we can limit the number of
> GPIOs
> somehow.
> 
> The devicetree binding already describes an `ngpios` property so
> perhaps
> we could make use of this to use the same properties struct instance
> for both
> controllers in the 2600: Require that the property be present for
> 2600-
> compatible devicetree nodes and test for its presence in probe(),
> then fall
> back to the hard-coded value in the config struct if it is not (this
> keeps
> devicetree compatibility for the 2400 and 2500 drivers).
> 
> This way we can eliminate the aspeed,ast2600-1-8v-gpio compatible
> string
> below (we just use aspeed,ast2600-gpio for both controllers).
> 
> Thoughts?

I like this idea. Once I have confirmation that all the 1.8V pins are
indeed input and output capable I'll send out a v3.

> 
> Andrew
> 
> > +	{ },
> > +};
> > +
> > +static const struct aspeed_gpio_config ast2600_1_8v_config =
> > +	/* 36 1.8V GPIOs */
> > +	{ .nr_gpios = 36, .props = ast2600_1_8v_bank_props, };
> > +
> >  static const struct of_device_id aspeed_gpio_of_table[] = {
> >  	{ .compatible = "aspeed,ast2400-gpio", .data = &ast2400_config,
> > },
> >  	{ .compatible = "aspeed,ast2500-gpio", .data = &ast2500_config,
> > },
> > +	{ .compatible = "aspeed,ast2600-gpio", .data = &ast2600_config,
> > },
> > +	{ .compatible = "aspeed,ast2600-1-8v-gpio",
> > +	  .data = &ast2600_1_8v_config, },
> >  	{}
> >  };
> >  MODULE_DEVICE_TABLE(of, aspeed_gpio_of_table);
> > -- 
> > 2.20.1
> > 
> >