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From:   Robert Richter <rrichter@marvell.com>
To:     Borislav Petkov <bp@alien8.de>
CC:     James Morse <james.morse@arm.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        "linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 02/24] EDAC, ghes: Fix grain calculation
Thread-Topic: [PATCH v2 02/24] EDAC, ghes: Fix grain calculation
Thread-Index: AQHVUQY528Xmn3pGVkWm7FH417vWZw==
Date:   Mon, 12 Aug 2019 12:05:25 +0000
Message-ID: <20190812120517.2kktugib244ujgvb@rric.localdomain>
References: <20190624150758.6695-1-rrichter@marvell.com>
 <20190624150758.6695-3-rrichter@marvell.com> <20190809131559.GF2152@zn.tnic>
 <20190812064147.5czmkj7e6hxgvje3@rric.localdomain>
 <20190812073221.GA23772@zn.tnic>
In-Reply-To: <20190812073221.GA23772@zn.tnic>
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On 12.08.19 09:32:22, Borislav Petkov wrote:
> On Mon, Aug 12, 2019 at 06:42:00AM +0000, Robert Richter wrote:

> > With the grain_bits calculation the mask is rounded up to the next
> > power of 2 value.
>=20
> mask	  =3D 0xffffffffff00ff00

grain =3D ~mask + 1

> ~mask	  =3D 0x0000000000ff00ff
> ~mask + 1 =3D 0x0000000000ff0100

grain_bits =3D fls_long(e->grain - 1);
grain_bits =3D 24

grain =3D 1 << grain_bits
grain =3D 0x1000000

So for masks in the range from 0xffffffffff000000 to
0xffffffffff7fffff we have grain_bits set to 24, which corresponds to
a grain of 0x1000000. Looks good to me.

>=20
> Your "trick" of adding a 1 to get to the most significant bit simply
> doesn't work here. Thus:
>=20
> "I guess we can leave it like that for now until some "inventive"
> firmware actually does it."

Fine to me.

-Robert