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MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="bTVt/3AHGmWN4vDu" Content-Disposition: inline In-Reply-To: X-BeenThere: openbmc@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development list for OpenBMC List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: openbmc@lists.ozlabs.org, Benjamin Fair , Michael Shen Errors-To: openbmc-bounces+openbmc=archiver.kernel.org@lists.ozlabs.org Sender: "openbmc" --bTVt/3AHGmWN4vDu Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Feb 09, 2022 at 12:20:00PM -0800, Ed Tanous wrote: > On Wed, Feb 9, 2022 at 11:56 AM Patrick Williams wrot= e: > > On Tue, Feb 08, 2022 at 04:23:12PM +0800, Michael Shen wrote: > > > On Tue, Feb 8, 2022 at 3:11 PM Patrick Williams w= rote: > > > > On Tue, Feb 08, 2022 at 01:10:37PM +0800, Michael Shen wrote: > > > BIOS owns the MUX select pin and it can decide who owns the SPD(I2C/I= 3C) bus. > > > From my understanding, BIOS only needs to read SPD during the POST st= age. > > > For the rest of time, BIOS will hand over the SPD bus to BMC. > > > > That seems like it might work. You'll have to deal with the time when = the BIOS > > has the mux in the BMC code somehow. Ideally I'd ask for the mux selec= t to also > > be fed to the BMC as an input GPIO so that you can differentiate betwee= n "we > > don't own the mux" and "all the devices are NAKing us". >=20 > This seems like a nitty gritty design detail that's best handled in > code when we review it. I think the important bit here is that there > are paths where this could work without a significant design issue. Just one subtlety. I wouldn't expect this, necessarily, to be in _our_ des= ign and/or code, except that we'd want to document the GPIO line like we do all others. I was trying to hint that "if I were involved in this hardware des= ign, I'd ask for...". If you leave it out, I'm sure it'll work _most_ of the ti= me just fine and it'll be your problem to debug it when it doesn't. --=20 Patrick Williams --bTVt/3AHGmWN4vDu Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEBGD9ii4LE9cNbqJBqwNHzC0AwRkFAmIELsoACgkQqwNHzC0A wRkDWBAAih0cuM4d5UtdZGFxcpwU+L4+UPxq0z5iSXnqNUDBlLRxzyyYk53QtB5N dAlZrQ56eOSaID6qyKHQBHbPVvr3Bt9wncphIjWqMxu1WtnxRf9qvJ3lMrt6gR4p cNNF1+zjwB6pHm1iw8RlbZxgVr1Uew/gbFUzDzRmCmKeKYbdjipDV0gk49/OWM2h lOCyRr6zWIus1JRF/tddCxbYozfvuZuVY2CFHJLbmnkVxplQydhV9UqXyiSu8fZ0 JQQj3GkA+I/S6kqJ3paU10w/5w4Uk63RRY1jzRubWsgyVqdkjQ9Y+u3G+hTfUm1/ kPTfVwVDa73yIQ7c7ocBK5CIrO0/3G0+x+pGdgktHXV5sQAk8ZE321AdiCZqLODx 7MStbeY5JLry7kIAet6l/0KB7HE6eey7VTVVogUz0dEvF8pYkeXUtGDwT3ZaROfl WlDbQPcXfHtzhwPV0baZBCpodoXLbEHeSXP/qpRFTPIEedR8eLFsAAlAuqkqLqsb B0YOxdo33NZre/7fMDRVE5VvrjLicfQlYTyo3gj/xFVXT5tInrjrONnBWPS/gY9E PAmftJSGI5E9ZLjO6ZCi0fjSzAkeClIJYaNnNtQc4AHM0ntexkRhhXvsrrBPgUVV 1jl3PGBxt2P5F9xD9i60CW20nhOoL0/xuGGCbYgCFbWVAliw8Qg= =Jncj -----END PGP SIGNATURE----- --bTVt/3AHGmWN4vDu--