Re: [PATCH net-next-2.6 v2] can: Topcliff: PCH_CAN driver: Fix build warnings - Marc Kleine-Budde

From: Marc Kleine-Budde <mkl-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
To: Tomoya MORINAGA <tomoya-linux-ECg8zkTtlr0C6LszWs/t0g@public.gmane.org>
Cc: andrew.chih.howe.khor-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
	Masayuki Ohtake
	<masa-korg-ECg8zkTtlr0C6LszWs/t0g@public.gmane.org>,
	Samuel Ortiz <sameo-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
	margie.foster-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
	netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public.gmane.org,
	yong.y.wang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
	kok.howg.ewe-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
	Wolfgang Grandegger <wg-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>,
	joel.clark-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org,
	"David S. Miller" <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>,
	Christian Pellegrin <chripell-VaTbYqLCNhc@public.gmane.org>,
	qi.wang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org
Subject: Re: [PATCH net-next-2.6 v2] can: Topcliff: PCH_CAN driver: Fix build warnings
Date: Thu, 11 Nov 2010 11:04:39 +0100	[thread overview]
Message-ID: <4CDBBFB7.70806@pengutronix.de> (raw)
In-Reply-To: <002501cb8186$b56a6280$66f8800a-a06+6cuVnkTSQfdrb5gaxUEOCMrvLtNR@public.gmane.org>

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On 11/11/2010 10:56 AM, Tomoya MORINAGA wrote:
>>>>> + if (priv->tx_obj == (PCH_OBJ_NUM + 1)) { /* Point tail Obj + 1 */
>>>>> +  while (ioread32(&priv->regs->treq2) & 0xfc00)
>>>>> +   udelay(1);
>>>
>>> When points tail of Tx message object,
>>> this driver waits until completion of all tx messaeg objects.
>>
>> Looping busy it not an option here.
>>
>>> Thus, application/driver ought not to be able to put Tx object exceed the number of tx message object.
>>> Thus I think these code(netif_stop_queue/netif_wake_queue) are completely redundant.
>>
>> Nope - please remove the waiting completely and convert your flow
>> control to netif_stop_queue/netif_wake_queue.
>>
> 
> I see.
> I will remove like above.
> 
> BTW, Let me know the reason.
> Could you explain the reason why you deny looping busy loop ?

That would kill performance.

cheers, Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |

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