linux-kernel - Re: [PATCH 1/2] cs5535-gpio: don't apply errata #36 to edge detect GPIOs

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Message-ID: <20101217180948.66ed5eef@queued.net>
Date:	Fri, 17 Dec 2010 18:09:48 -0800
From:	Andres Salomon <dilinger@...ued.net>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, linux-geode@...ts.infradead.org,
	dsd@...top.org, pgf@...top.org
Subject: Re: [PATCH 1/2] cs5535-gpio: don't apply errata #36 to edge detect
 GPIOs

Note: these two patches fix problems with commit 853ff883, so they
should definitely go in for 3.6.37.


On Wed, 15 Dec 2010 11:28:07
-0800 Andres Salomon <dilinger@...ued.net> wrote:

> 
> The edge detect status GPIOs function differently from the other
> atomic model CS5536 GPIO registers; writing 1 to the high bits clears
> the GPIO, but writing 1 to the lower bits also clears the bit.  This
> means that read-modify-write doesn't actually work for it, so don't
> apply the errata here.  If a negative edge status gets lost after
> resume.. well, we tried our best!
> 
> Signed-off-by: Andres Salomon <dilinger@...ued.net>
> Tested-by: Daniel Drake <dsd@...top.org>
> ---
>  drivers/gpio/cs5535-gpio.c |   15 +++++++++++----
>  1 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpio/cs5535-gpio.c b/drivers/gpio/cs5535-gpio.c
> index 599f6c9..79eb9c5 100644
> --- a/drivers/gpio/cs5535-gpio.c
> +++ b/drivers/gpio/cs5535-gpio.c
> @@ -56,15 +56,22 @@ static struct cs5535_gpio_chip {
>   * registers, see include/linux/cs5535.h.
>   */
>  
> -static void errata_outl(u32 val, unsigned long addr)
> +static void errata_outl(struct cs5535_gpio_chip *chip, u32 val,
> +		unsigned int reg)
>  {
> +	unsigned long addr = chip->base + 0x80 + reg;
> +
>  	/*
>  	 * According to the CS5536 errata (#36), after suspend
>  	 * a write to the high bank GPIO register will clear all
>  	 * non-selected bits; the recommended workaround is a
>  	 * read-modify-write operation.
> +	 *
> +	 * Don't apply this errata to the edge status GPIOs, as
> writing
> +	 * to their lower bits will clear them.
>  	 */
> -	val |= inl(addr);
> +	if (reg != GPIO_POSITIVE_EDGE_STS && reg !=
> GPIO_NEGATIVE_EDGE_STS)
> +		val |= inl(addr);
>  	outl(val, addr);
>  }
>  
> @@ -76,7 +83,7 @@ static void __cs5535_gpio_set(struct
> cs5535_gpio_chip *chip, unsigned offset, outl(1 << offset, chip->base
> + reg); else
>  		/* high bank register */
> -		errata_outl(1 << (offset - 16), chip->base + 0x80 +
> reg);
> +		errata_outl(chip, 1 << (offset - 16), reg);
>  }
>  
>  void cs5535_gpio_set(unsigned offset, unsigned int reg)
> @@ -98,7 +105,7 @@ static void __cs5535_gpio_clear(struct
> cs5535_gpio_chip *chip, unsigned offset, outl(1 << (offset + 16),
> chip->base + reg); else
>  		/* high bank register */
> -		errata_outl(1 << offset, chip->base + 0x80 + reg);
> +		errata_outl(chip, 1 << offset, reg);
>  }
>  
>  void cs5535_gpio_clear(unsigned offset, unsigned int reg)
--
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