linux-kernel - Re: [PATCH net-next-2.6 v2] can: Topcliff: PCH

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Date:	Thu, 11 Nov 2010 11:04:39 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Tomoya MORINAGA <tomoya-linux@....okisemi.com>
CC:	Wolfgang Grandegger <wg@...ndegger.com>,
	"David S. Miller" <davem@...emloft.net>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Christian Pellegrin <chripell@...e.org>,
	Barry Song <21cnbao@...il.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	socketcan-core@...ts.berlios.de, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	andrew.chih.howe.khor@...el.com, qi.wang@...el.com,
	margie.foster@...el.com, yong.y.wang@...el.com,
	Masayuki Ohtake <masa-korg@....okisemi.com>,
	kok.howg.ewe@...el.com, joel.clark@...el.com
Subject: Re: [PATCH net-next-2.6 v2] can: Topcliff: PCH_CAN driver: Fix build
 warnings

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     |
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