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List:       intel-wired-lan
Subject:    [Intel-wired-lan] [question] i40e: Question about the i40e_clear_pxe_mode() function
From:       "Xuguizhu (Guzhu Xu, Intelligent Computing Business Dept)" <xuguizhu () huawei ! com>
Date:       2019-03-27 10:58:35
Message-ID: 315E3AFC3F1FCC4A88C68B5581547E0682A9D1D5 () dggemm513-mbx ! china ! huawei ! com
[Download RAW message or body]

In the process of testing the NCSI function of the X722 NIC, when we started the \
ubuntu 18.04 system using the legacy mode, the system was put into the panic state by \
injecting a fault into the system through the "echo c > /proc/sysrq-trigger" command. \
When using the i40e driver in the ubuntu system, NCSI is broken after the injection \
failure. After upgrading the kernel to 5.1-rc2, the problem still exists. After using \
the driver released in sourceforge.net, the same test is performed and the NSCI \
function is normal.

After comparing the drivers of the two branches, we found that this problem may be \
related to the i40e_clear_pxe_mode() function. The code for the I40E driver released \
in the kernel community is as follows: void i40e_clear_pxe_mode(struct i40e_hw *hw)
{
	u32 reg;

	if (i40e_check_asq_alive(hw))
		i40e_aq_clear_pxe_mode(hw, NULL);

	/* Clear single descriptor fetch/write-back mode */
	reg = rd32(hw, I40E_GLLAN_RCTL_0);

	if (hw->revision_id == 0) {
		/* As a work around clear PXE_MODE instead of setting it */
		wr32(hw, I40E_GLLAN_RCTL_0, (reg & (~I40E_GLLAN_RCTL_0_PXE_MODE_MASK)));
	} else {
		wr32(hw, I40E_GLLAN_RCTL_0, (reg | I40E_GLLAN_RCTL_0_PXE_MODE_MASK));
	}
}

The code for the i40e_clear_pxe_mode() function in the driver released in \
sourceforge.net is as follows: void i40e_clear_pxe_mode(struct i40e_hw *hw)
{
	if (i40e_check_asq_alive(hw))
		i40e_aq_clear_pxe_mode(hw, NULL);
}

We only modify the code of the i40e_clear_pxe_mode() function based on the code \
released by sourceforge.net. After testing, we can still reproduce the issue of NCSI \
break.

Our question is: what is the reason for adding this code, how to solve the problem we \
are now facing.




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