Re: [Intel-wired-lan] [PATCH linux-next] e1000: Remove redundant statement

On Wed, Oct 20, 2021 at 11:08:11AM -0700, Jesse Brandeburg wrote:

Apologies for the duplicates, mail from my intel account going out
through outlook.com is not being delivered.

On Wed, Oct 20, 2021 at 7:00 AM Simon Horman [off-list ref] wrote:

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Value stored to 'ctrl_reg' is never read.

I agree this does seem to be the case.

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Reported-by: Zeal Robot <redacted>
Signed-off-by: luo penghao <redacted>

Reviewed-by: Simon Horman <horms@kernel.org>

Thanks for the review, but (davem/kuba) please do not apply.

Thanks, and sorry for misunderstanding the patch.

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@@ -1215,8 +1215,6 @@ static int e1000_integrated_phy_loopback(struct e1000_adapter *adapter)
              e1000_write_phy_reg(hw, PHY_CTRL, 0x8140);
      }

-     ctrl_reg = er32(CTRL);

Thanks for your patch, but this change is not safe. you're removing a
read that could do two things. The first is that the read "flushes"
the write just above to PCI (it's a PCI barrier), and the second is
that the read can have some side effects.

If this change must be done, the code should be to remove the
assignment to ctrl_reg, but leave the read, so the line would just
look like:
        er32(CTRL);

This will get rid of the warning and not change the flow from the
hardware perspective.

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-
      /* force 1000, set loopback */
      e1000_write_phy_reg(hw, PHY_CTRL, 0x4140);

Please do not apply this.