netdev - Re: [patch 2.6.24-git] net/enc28j60: oops fix, low power mode

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Date:	Wed, 06 Feb 2008 18:11:30 +0100
From:	Claudio Lanconelli <lanconelli.claudio@...ar.com>
To:	netdev@...r.kernel.org
CC:	David Brownell <david-b@...bell.net>
Subject: Re: [patch 2.6.24-git] net/enc28j60: oops fix, low power mode

David Brownell wrote:
> From: David Brownell <dbrownell@...rs.sourceforge.net>
>
> Prevent unaligned packet oops on enc28j60 packet RX.
>   
How can I reproduce the unaligned packet oops? Did you use any utilities 
to force this condition?
> Keep enc28j60 chips in low-power mode when they're not in use.
> At typically 120 mA, these chips run hot even when idle.  Low
> power mode cuts that power usage by a factor of around 100.
>   
Good idea, but with your patch applied, after some ifconfig down - 
ifconfig up cycle, the
enc28j60 is left in an unknown state and it doesn' Rx/Tx anything.
In such cases If I dump the counters with ifconfig I got rx error 
counter > 0 and the RX and TX packets counters are freezed.
Actually I don't know what causes the freeze, it needs investigation. 
The cause can be the rx error condition or the power down/up commands.
May be receiving packets while it's going to wakeup causes problems.

Can you split the patch in 2 parts, unaligned rx and power save?

> +/*
> + * Low power mode shrinks power consumption about 100x, so we'd like
> + * the chip to be in that mode whenever it's inactive.
> + */
> +static void enc28j60_lowpower(struct enc28j60_net *priv, bool is_low)
> +{
> +	int	tmp;
> +
> +	dev_dbg(&priv->spi->dev, "%s power...\n", is_low ? "low" : "high");
>   
use
if(netif_msg_drv(priv)) printk(...
instead of dev_dbg(), please.
Doing so we can switch on/off messages runtime using ethtool.

> +
> +	mutex_lock(&priv->lock);
> +	if (is_low) {
> +		nolock_reg_bfclr(priv, ECON1, ECON1_RXEN);
> +		for (;;) {
> +			tmp = nolock_regb_read(priv, ESTAT);
> +			if (!(tmp & ESTAT_RXBUSY))
> +				break;
> +		}
>   
Avoid infinite waiting loops, please.
Look at enc28j60_phy_read() for example.
> +		for (;;) {
> +			tmp = nolock_regb_read(priv, ECON1);
> +			if (!(tmp & ECON1_TXRTS))
> +				break;
> +		}
>   
idem
> +		/* ECON2_VRPS was set during initialization */
> +		nolock_reg_bfset(priv, ECON2, ECON2_PWRSV);
> +	} else {
> +		nolock_reg_bfclr(priv, ECON2, ECON2_PWRSV);
> +		for (;;) {
> +			tmp = nolock_regb_read(priv, ESTAT);
> +			if (tmp & ESTAT_CLKRDY)
> +				break;
> +		}
>   
idem

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