Messages in this thread | | | Subject | Re: [PATCH] net: ethernet: et131x: Remove redundant register read | From | Mark Einon <> | Date | Fri, 17 Jul 2020 16:21:51 +0100 |
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On Fri, 2020-07-17 at 15:40 +0200, Andrew Lunn wrote: > On Fri, Jul 17, 2020 at 02:21:35PM +0100, Mark Einon wrote: > > Following the removal of an unused variable assignment (remove > > unused variable 'pm_csr') the associated register read can also go, > > as the read also occurs in the subsequent > > call. > > Hi Mark > > Do you have any hardware documentation which indicates these read are > not required? Have you looked back through the git history to see if > there are any comments about these read? > > Hardware reads which appear pointless are sometimes very important to > actually make the hardware work. > > Andrew
Hi Andrew,
Yes - I'm aware of such effects. In the original vendor driver ( https://gitlab.com/einonm/Legacy-et131x) the read of this register ( pm_phy_sw_coma) is not wrapped in a function call and is always called once when needed.
Also in the current kernel driver et1310_in_phy_coma() is called a few other times without the removed read being made.
The datasheet I have for a similar device (et1011) doesn't say anything other than the register should be read/write.
So I think this is a safe thing to do.
Best regards,
Mark
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