linux-kernel - Re: [PATCH v1 RFC 6/7] Add MIB counter reading support

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Date:   Mon, 9 Oct 2017 21:54:43 +0200
From:   Pavel Machek <pavel@....cz>
To:     Tristram.Ha@...rochip.com
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ruediger Schmitt <ruediger.schmitt@...lips.com>,
        muvarov@...il.com, nathan.leigh.conrad@...il.com,
        vivien.didelot@...oirfairelinux.com, UNGLinuxDriver@...rochip.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 RFC 6/7] Add MIB counter reading support

Hi!

> From: Tristram Ha <Tristram.Ha@...rochip.com>
> 
> Add MIB counter reading support.
> Rename ksz_9477_reg.h to ksz9477_reg.h for consistency as the product
> name is always KSZ####.
> Header file ksz_priv.h no longer contains any chip specific data.

Nothing obviously wrong here, but if you are doing another iteration,
it would be nice to separate "Rename ksz_9477_reg.h to ksz9477_reg.h"
from the code changes.

Best regards,

> +	timeout = 1000;
> +	do {
> +		ksz_pread32(dev, port, REG_PORT_MIB_CTRL_STAT__4,
> +			    &data);
> +		usleep_range(1, 10);
> +		if (!(data & MIB_COUNTER_READ))
> +			break;
> +	} while (timeout-- > 0);

1000 iterations, 1usec each, so 1msec, but you allow up to 10 msec. Interesting.

> +	/* failed to read MIB. get out of loop */
> +	if (!timeout) {
> +		dev_dbg(dev->dev, "Failed to get MIB\n");
> +		return;
> +	}

Are you sure this works? AFAICT "timeout" will underflow, so !timeout
will not trigger.


> -static void ksz_get_ethtool_stats(struct dsa_switch *ds, int port,
> -				  uint64_t *buf)
> -{
> -	struct ksz_device *dev = ds->priv;
> -	int i;
> -	u32 data;
> -	int timeout;
> -
> -	mutex_lock(&dev->stats_mutex);
> -
> -	for (i = 0; i < TOTAL_SWITCH_COUNTER_NUM; i++) {
> -		data = MIB_COUNTER_READ;
> -		data |= ((mib_names[i].index & 0xFF) << MIB_COUNTER_INDEX_S);
> -		ksz_pwrite32(dev, port, REG_PORT_MIB_CTRL_STAT__4, data);
> -
> -		timeout = 1000;
> -		do {
> -			ksz_pread32(dev, port, REG_PORT_MIB_CTRL_STAT__4,
> -				    &data);
> -			usleep_range(1, 10);
> -			if (!(data & MIB_COUNTER_READ))
> -				break;
> -		} while (timeout-- > 0);
> -
> -		/* failed to read MIB. get out of loop */
> -		if (!timeout) {
> -			dev_dbg(dev->dev, "Failed to get MIB\n");
> -			break;
> -		}

Hmm. Bug was there already...
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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