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RE: [PATCH] stmmac: Discard masked flags in interrupt status register

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  RE: [PATCH] stmmac: Discard masked flags in interrupt status  register Alexey Brodkin <Alexey.Brodkin@synopsys.com> - 2017-02-01 21:30 +0100
    Re: [PATCH] stmmac: Discard masked flags in interrupt status  register David Miller <davem@davemloft.net> - 2017-02-01 22:10 +0100

#1571962 — RE: [PATCH] stmmac: Discard masked flags in interrupt status register

Hi David, all,

> -----Original Message-----
> From: David Miller [mailto:davem@davemloft.net]
> Sent: Monday, January 30, 2017 2:16 AM
> To: Alexey.Brodkin@synopsys.com
> Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org;
> peppe.cavallaro@st.com; fabrice.gasnier@st.com; manabian@gmail.com;
> preid@electromag.com.au; alexandre.torgue@gmail.com;
> Vineet.Gupta1@synopsys.com
> Subject: Re: [PATCH] stmmac: Discard masked flags in interrupt status
> register
> 
> From: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
> Date: Fri, 27 Jan 2017 15:24:43 +0300
> 
> > DW GMAC databook says the following about bits in "Register 15
> > (Interrupt Mask Register)":
> > --------------------------->8-------------------------
> > When set, this bit __disables_the_assertion_of_the_interrupt_signal__
> > because of the setting of XXX bit in Register 14 (Interrupt Status
> > Register).
> > --------------------------->8-------------------------
> >
> > In fact even if we mask one bit in the mask register it doesn't
> > prevent corresponding bit to appear in the status register, it only
> > disables interrupt generation for corresponding event.
> >
> > But currently we expect a bit different behavior: status bits to be in
> > sync with their masks, i.e. if mask for bit A is set in the mask
> > register then bit A won't appear in the interrupt status register.
> >
> > This was proven to be incorrect assumption, see discussion here [1].
> > That misunderstanding causes unexpected behaviour of the GMAC, for
> > example we were happy enough to just see bogus messages about link
> > state changes.
> >
> > So from now on we'll be only checking bits that really may trigger an
> > interrupt.
> >
> > [1] https://lkml.org/lkml/2016/11/3/413
> >
> > Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
> 
> This looks good, applied, thanks.

May we have that one back-ported to stable branches starting from 4.8.x?

That issue started to appear due to a change from pr_debug() to pr_info() in commit
70523e639bf8 ("drivers: net: stmmac: reworking the PCS code.").

-Alexey

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#1571978

From: Alexey Brodkin <Alexey.Brodkin@synopsys.com>
Date: Wed, 1 Feb 2017 20:22:22 +0000

> May we have that one back-ported to stable branches starting from 4.8.x?
> 
> That issue started to appear due to a change from pr_debug() to pr_info() in commit
> 70523e639bf8 ("drivers: net: stmmac: reworking the PCS code.").

Sure, queued up for -stable.

Thanks.

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