RE: [PATCH net-next v3 2/3] net: txgbe: Reset hardware

On Tuesday, October 11, 2022 9:55 AM, Andrew Lunn wrote:

quoted

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So you have an IO barrier before and a read barrier afterwards.  So
all i think you need is a

mb(), not a

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full rd32().

   Andrew

I think we need a readl(), because there are problems that sometimes
IO is not synchronized with flushing memory on some domestic cpu platforms.
It can become a serious problem, causing register error configurations.

So please document this as a comment in the code.

I also then start to wounder if more such flushes are needed, to handle this broken hardware.
Do you have a detailed description of what actually goes wrong? Otherwise how do you know
when such a flush is needed?

   Andrew

We don't know the exact behavior of the platforms, but it works under this workaround. That is, read
the register once after the write operations.