linux-kernel - Re: Spurious timeouts in mvmdio

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Date:	Mon, 16 Dec 2013 18:28:03 +0000
From:	Leigh Brown <leigh@...inno.co.uk>
To:	Nicolas Schichan <nschichan@...ebox.fr>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Jason Cooper <jason@...edaemon.net>, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Florian Fainelli <florian@...nwrt.org>,
	"David S. Miller" <davem@...emloft.net>,
	linux-arm-kernel@...ts.infradead.org,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: Spurious timeouts in mvmdio

On 2013-12-16 18:07, Nicolas Schichan wrote:
> On 12/04/2013 12:42 AM, Russell King - ARM Linux wrote:
>> Alternatively, code it like this instead.
>> 
>>   drivers/net/ethernet/marvell/mvmdio.c |   32 
>> +++++++++++++++-----------------
>>   1 files changed, 15 insertions(+), 17 deletions(-)
>> 
>> diff --git a/drivers/net/ethernet/marvell/mvmdio.c 
>> b/drivers/net/ethernet/marvell/mvmdio.c
>> index 7354960b583b..a6f59831fc5b 100644
>> --- a/drivers/net/ethernet/marvell/mvmdio.c
>> +++ b/drivers/net/ethernet/marvell/mvmdio.c
>> @@ -76,31 +76,29 @@ static int orion_mdio_wait_ready(struct mii_bus 
>> *bus)
>>   {
>>   	struct orion_mdio_dev *dev = bus->priv;
>>   	unsigned long timeout = usecs_to_jiffies(MVMDIO_SMI_TIMEOUT);
>> -	unsigned long end = jiffies + timeout;
>> -	int timedout = 0;
>> 
>> -	while (1) {
>> -	        if (orion_mdio_smi_is_done(dev))
>> +	if (dev->err_interrupt > 0) {
>> +		if (wait_event_timeout(dev->smi_busy_wait,
>> +				       orion_mdio_smi_is_done(dev),
>> +				       1 + timeout))
>>   			return 0;
>> -	        else if (timedout)
>> -			break;
>> +	} else {
>> +		unsigned long end = jiffies + timeout;
>> 
>> -	        if (dev->err_interrupt <= 0) {
>> -			usleep_range(MVMDIO_SMI_POLL_INTERVAL_MIN,
>> -				     MVMDIO_SMI_POLL_INTERVAL_MAX);
>> +		while (1) {
>> +	        	if (orion_mdio_smi_is_done(dev))
>> +				return 0;
>> 
>>   			if (time_is_before_jiffies(end))
>> -				++timedout;
>> -	        } else {
>> -			wait_event_timeout(dev->smi_busy_wait,
>> -				           orion_mdio_smi_is_done(dev),
>> -				           timeout);
>> -
>> -			++timedout;
>> -	        }
>> +				break;
>> +
>> +			usleep_range(MVMDIO_SMI_POLL_INTERVAL_MIN,
>> +				     MVMDIO_SMI_POLL_INTERVAL_MAX);
>> +		}
>>   	}
>> 
>>   	dev_err(bus->parent, "Timeout: SMI busy for too long\n");
>> +
>>   	return  -ETIMEDOUT;
>>   }
> 
> Hi Russell,
> 
> I did not find any commit for this in 3.13-rc4.
> 
> Would you prefer I submit my attempt at refactoring the
> orion_mdio_wait_ready() code ?

I prefer this patch (which I think you originally proposed) because it 
is just as
correct and the code size is a bit smaller in arm mode, and the same 
size in thumb
mode (on my compiler gcc 4.7.2, at least).  I coded the loop in that way 
to make it
small.

I don't mind submitting it to David as I made the mistake in the first 
place.

Regards,

Leigh.

diff --git a/drivers/net/ethernet/marvell/mvmdio.c 
b/drivers/net/ethernet/marvell/mvmdio.c
index 7354960..a42a750 100644
--- a/drivers/net/ethernet/marvell/mvmdio.c
+++ b/drivers/net/ethernet/marvell/mvmdio.c
@@ -92,6 +92,12 @@ static int orion_mdio_wait_ready(struct mii_bus *bus)
  			if (time_is_before_jiffies(end))
  				++timedout;
  	        } else {
+			/* wait_event_timeout does not guarantee a delay of at
+			 * least one whole jiffie, so timeout must be no less
+			 * than two.
+			 */
+			 if (timeout < 2)
+			 	timeout = 2;
  			wait_event_timeout(dev->smi_busy_wait,
  				           orion_mdio_smi_is_done(dev),
  				           timeout);

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