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Date: Mon, 11 Jun 2018 11:37:34 +1000
From: Nicholas Piggin <npiggin@gmail.com>
To: Michal =?UTF-8?B?U3VjaMOhbmVr?= <msuchanek@suse.de>
Cc: linuxppc-dev@lists.ozlabs.org, Benjamin Herrenschmidt
 <benh@kernel.crashing.org>
Subject: Re: [RFC PATCH] powerpc/64s: remove POWER9 DD1 support
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On Sun, 10 Jun 2018 22:58:11 +0200
Michal Such=C3=A1nek <msuchanek@suse.de> wrote:

> On Sun, 10 Jun 2018 23:30:27 +1000
> Nicholas Piggin <npiggin@gmail.com> wrote:
>=20
> > POWER9 DD1 was never a product. It is no longer supported by upstream
> > firmware, and it is not effectively supported in Linux due to lack of
> > testing.
> >  =20
>=20
> > diff --git a/arch/powerpc/kvm/book3s_xive_template.c
> > b/arch/powerpc/kvm/book3s_xive_template.c index
> > 99c3620b40d9..487f1f6650cc 100644 ---
> > a/arch/powerpc/kvm/book3s_xive_template.c +++
> > b/arch/powerpc/kvm/book3s_xive_template.c @@ -25,18 +25,6 @@ static
> > void GLUE(X_PFX,ack_pending)(struct kvmppc_xive_vcpu *xc) */
> >  	eieio();
> > =20
> > -	/*
> > -	 * DD1 bug workaround: If PIPR is less favored than CPPR
> > -	 * ignore the interrupt or we might incorrectly lose an IPB
> > -	 * bit.
> > -	 */
> > -	if (cpu_has_feature(CPU_FTR_POWER9_DD1)) {
> > -		__be64 qw1 =3D __x_readq(__x_tima + TM_QW1_OS);
> > -		u8 pipr =3D be64_to_cpu(qw1) & 0xff;
> > -		if (pipr >=3D xc->hw_cppr)
> > -			return;
> > -	}
> > -
> >  	/* Perform the acknowledge OS to register cycle. */
> >  	ack =3D be16_to_cpu(__x_readw(__x_tima + TM_SPC_ACK_OS_REG));
> > =20
> > @@ -105,7 +93,7 @@ static void GLUE(X_PFX,source_eoi)(u32 hw_irq,
> > struct xive_irq_data *xd) *
> >  		 * For LSIs, using the HW EOI cycle works around a
> > problem
> >  		 * on P9 DD1 PHBs where the other ESB accesses don't
> > work
> > -		 * properly.
> > +		 * properly. XXX: can this be removed?
> >  		 */
> >  		if (xd->flags & XIVE_IRQ_FLAG_LSI)
> >  			__x_readq(__x_eoi_page(xd) + =20
>=20
> Maybe this should be really removed or the comment changed to why it is
> still useful?

Good point, I meant to ask Ben about that.

Thanks,
Nick