From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Roese Date: Mon, 2 May 2011 13:50:42 +0200 Subject: [U-Boot] PPC405EX CHIP_21 erratum In-Reply-To: <4DBAED2A.4030705@harris.com> References: <4DBAED2A.4030705@harris.com> Message-ID: <201105021350.43119.sr@denx.de> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hi Steve, On Friday 29 April 2011 18:54:02 Steven A. Falco wrote: > We've been bitten by the PPC405EX CHIP_21 erratum. How did it affect you exactly? Was an incorrect PVR detected? Did this result in some problems (Linux etc)? > I've looked through the > U-Boot code, but it doesn't appear that there is a work-around for this > one. Correct, there currently is no workaround. > The following patch is my adaptation of AMCC's suggestion as to the fix. > But I have to say that I don't care for it, if for no other reason that it > will break if a rev E comes out. > > Also, I made it #ifdef'd on CONFIG_405EX, but it will not work on a 405EXr. > And I have seen a 405EX report its PVR as if it were a 405EXr. It's not > looking good for the suggested work-around. > > AMCC claims this can be fixed in hardware, by always doing a double reset. > Naturally, that is hard to implement and would mean massive rework of > existing boards. Yes, there are many 405EX(r) boards in the field already. Such an hardware workaround should really be avoided if possible. > So I am contemplating a different work-around, whereby software always > resets the board on a cold boot (if such a thing can be reliably > detected). That would hopefully be the equivalent of the hardware double > reset, and would not be dependent on specific PVR values, making it more > "future proof". > > Has anyone else run across this? Do you have similar concerns about the > patch? No, I have not seen this problem before. And yes, I would also prefer your "alternative suggestion", with the always reboot after powerup optionally built into the U-Boot image. But as you already mentioned, we would have to find a way to reliably detect the powerup reset, so that we don't end in an reset-loop. Cheers, Stefan -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-0 Fax: (+49)-8142-66989-80 Email: office at denx.de