linux-kernel - Re: [PATCH net v2 2/2] net: ixgbe: Use new PCI_DEV_FLAGS_NO_RELAXED

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Date:   Fri, 18 Aug 2017 08:39:23 +0800
From:   Ding Tianhong <dingtianhong@...wei.com>
To:     "Tantilov, Emil S" <emil.s.tantilov@...el.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "sparclinux@...r.kernel.org" <sparclinux@...r.kernel.org>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
        "alexander.duyck@...il.com" <alexander.duyck@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linuxarm@...wei.com" <linuxarm@...wei.com>
Subject: Re: [PATCH net v2 2/2] net: ixgbe: Use new
 PCI_DEV_FLAGS_NO_RELAXED_ORDERING flag



On 2017/8/17 22:17, Tantilov, Emil S wrote:

>> 	ret_val = ixgbe_start_hw_generic(hw);
>>
>> -#ifndef CONFIG_SPARC
>> -	/* Disable relaxed ordering */
>> -	for (i = 0; ((i < hw->mac.max_tx_queues) &&
>> -	     (i < IXGBE_DCA_MAX_QUEUES_82598)); i++) {
>> -		regval = IXGBE_READ_REG(hw, IXGBE_DCA_TXCTRL(i));
>> -		regval &= ~IXGBE_DCA_TXCTRL_DESC_WRO_EN;
>> -		IXGBE_WRITE_REG(hw, IXGBE_DCA_TXCTRL(i), regval);
>> -	}
>> +	if (!pcie_relaxed_ordering_enabled(adapter->pdev)) {
> 
> As Alex mentioned there is no need for this check in any form.
> 
> The HW defaults to Relaxed Ordering enabled unless it is disabled in 
> the PCIe Device Control Register. So the above logic is already done by HW.
> 
> All you have to do is strip the code disabling relaxed ordering.
> 

Hi Tantilov:

I misunderstood Alex's suggestion, But I still couldn't find the logic where
the HW disable the Relaxed Ordering when the PCIe Device Control Register
disable it, can you point it out?

Thanks
Ding

> Thanks,
> Emil
> 
> 
> .
>