Subject: Re: [PATCH v11 06/14] peci: Add Aspeed PECI adapter driver

From: Andy Shevchenko <[email-masked]>
Date: Wed, 11 Dec 2019 22:28:18 +0200

On Wed, Dec 11, 2019 at 11:46:16AM -0800, Jae Hyun Yoo wrote:
> This commit adds Aspeed PECI adapter driver for Aspeed
> AST24xx/25xx/26xx SoCs.

...

> +#define   ASPEED_PECI_CMD_IDLE_MASK		(ASPEED_PECI_CMD_STS_MASK | \
> +						 ASPEED_PECI_CMD_PIN_MON)

Better looking when the value completely occupies second line without touching
the first.

...

> +static int aspeed_peci_check_idle(struct aspeed_peci *priv)
> +{
> +	ulong timeout = jiffies + usecs_to_jiffies(ASPEED_PECI_IDLE_CHECK_TIMEOUT_USEC);
> +	u32 cmd_sts;

Like in the previous patch this one has hard to read timeout loops with inefficient code.

> +	for (;;) {
> +		cmd_sts = readl(priv->base + ASPEED_PECI_CMD);
> +		if (!(cmd_sts & ASPEED_PECI_CMD_IDLE_MASK))
> +			break;

> +		if (time_after(jiffies, timeout)) {

This is actually main exit condition (vs. infinite loop).

> +			cmd_sts = readl(priv->base + ASPEED_PECI_CMD);

This make no sense. If you would like to have one more iteration, just spell it
explicitly.

> +			break;
> +		}

> +		usleep_range((ASPEED_PECI_IDLE_CHECK_INTERVAL_USEC >> 2) + 1,
> +			     ASPEED_PECI_IDLE_CHECK_INTERVAL_USEC);
> +	}
> +

> +	return !(cmd_sts & ASPEED_PECI_CMD_IDLE_MASK) ? 0 : -ETIMEDOUT;

Ditto.

> +}

Now look at the other variant:

	do {
		...do something...
		if (success)
			return 0;
		usleep(...);
	} while (time_before(...));

	return -ETIMEDOUT;

* Easy
* less LOCs
* guaranteed always to be at least one iteration
* has explicitly spelled exit condition

BUT!

In this very case you may do even better if you read iopoll.h, i.e
readl_poll_timeout() has this functionality embedded in the macro.

-- 
With Best Regards,
Andy Shevchenko

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