linux-kernel - Re: [PATCH RESEND 3/4] mfd: arizona: Update arizona_poll

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Date:   Wed, 8 Feb 2017 10:04:58 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
Cc:     linux-kernel@...r.kernel.org, patches@...nsource.wolfsonmicro.com
Subject: Re: [PATCH RESEND 3/4] mfd: arizona: Update arizona_poll_reg to take
 a timeout in milliseconds

On Tue, 31 Jan 2017, Charles Keepax wrote:

> Currently, we specify the timeout in terms of the number of polls but it
> is more clear from a user of the functions perspective to specify the
> timeout directly in milliseconds, as such update the function to these new
> semantics.
> 
> Signed-off-by: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
> ---
>  drivers/mfd/arizona-core.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mfd/arizona-core.c b/drivers/mfd/arizona-core.c
> index 4cb34c3..ae4cdc4 100644
> --- a/drivers/mfd/arizona-core.c
> +++ b/drivers/mfd/arizona-core.c
> @@ -235,14 +235,18 @@ static irqreturn_t arizona_overclocked(int irq, void *data)
>  	return IRQ_HANDLED;
>  }
>  
> +#define ARIZONA_REG_POLL_DELAY_MS 5
> +
>  static int arizona_poll_reg(struct arizona *arizona,
> -			    int timeout, unsigned int reg,
> +			    int timeout_ms, unsigned int reg,
>  			    unsigned int mask, unsigned int target)
>  {
> +	unsigned int npolls = (timeout_ms + ARIZONA_REG_POLL_DELAY_MS - 1) /
> +			      ARIZONA_REG_POLL_DELAY_MS;

Why the over-complication?

Shouldn't this just be "timeout_ms / ARIZONA_REG_POLL_DELAY_MS"?

>  	unsigned int val = 0;
>  	int ret, i;
>  
> -	for (i = 0; i < timeout; i++) {
> +	for (i = 0; i < npolls; i++) {
>  		ret = regmap_read(arizona->regmap, reg, &val);
>  		if (ret != 0) {
>  			dev_err(arizona->dev, "Failed to read reg 0x%x: %d\n",
> @@ -253,7 +257,8 @@ static int arizona_poll_reg(struct arizona *arizona,
>  		if ((val & mask) == target)
>  			return 0;
>  
> -		usleep_range(1000, 5000);
> +		usleep_range((ARIZONA_REG_POLL_DELAY_MS * 1000) / 2,
> +			     ARIZONA_REG_POLL_DELAY_MS * 1000);

I'm sure there is a macro for conversion from ms to us.

By using such a wide range, you are now not honouring the timeout set
by the caller by as much as 50%.

>  	}
>  
>  	dev_err(arizona->dev, "Polling reg 0x%x timed out: %x\n", reg, val);
> @@ -269,7 +274,7 @@ static int arizona_wait_for_boot(struct arizona *arizona)
>  	 * we won't race with the interrupt handler as it'll be blocked on
>  	 * runtime resume.
>  	 */
> -	ret = arizona_poll_reg(arizona, 5, ARIZONA_INTERRUPT_RAW_STATUS_5,
> +	ret = arizona_poll_reg(arizona, 25, ARIZONA_INTERRUPT_RAW_STATUS_5,
>  			       ARIZONA_BOOT_DONE_STS, ARIZONA_BOOT_DONE_STS);
>  
>  	if (!ret)
> @@ -339,7 +344,7 @@ static int arizona_enable_freerun_sysclk(struct arizona *arizona,
>  			ret);
>  		return ret;
>  	}
> -	ret = arizona_poll_reg(arizona, 25, ARIZONA_INTERRUPT_RAW_STATUS_5,
> +	ret = arizona_poll_reg(arizona, 125, ARIZONA_INTERRUPT_RAW_STATUS_5,
>  			       ARIZONA_FLL1_CLOCK_OK_STS,
>  			       ARIZONA_FLL1_CLOCK_OK_STS);
>  	if (ret)
> @@ -403,7 +408,7 @@ static int wm5102_apply_hardware_patch(struct arizona *arizona)
>  		goto err;
>  	}
>  
> -	ret = arizona_poll_reg(arizona, 5, ARIZONA_WRITE_SEQUENCER_CTRL_1,
> +	ret = arizona_poll_reg(arizona, 25, ARIZONA_WRITE_SEQUENCER_CTRL_1,
>  			       ARIZONA_WSEQ_BUSY, 0);
>  	if (ret)
>  		regmap_write(arizona->regmap, ARIZONA_WRITE_SEQUENCER_CTRL_0,

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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