Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933468AbdDFSNl (ORCPT ); Thu, 6 Apr 2017 14:13:41 -0400 Received: from mail.free-electrons.com ([62.4.15.54]:50598 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754889AbdDFSN1 (ORCPT ); Thu, 6 Apr 2017 14:13:27 -0400 Date: Thu, 6 Apr 2017 20:13:24 +0200 From: Alexandre Belloni To: Ben Hutchings Cc: Sebastian Reichel , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 4.4 23/26] power: reset: at91-poweroff: timely shutdown LPDDR memories Message-ID: <20170406181324.horsqbprkajwuern@piout.net> References: <20170406083604.362636628@linuxfoundation.org> <20170406083605.797902629@linuxfoundation.org> <1491500739.10415.38.camel@codethink.co.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1491500739.10415.38.camel@codethink.co.uk> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1646 Lines: 53 On 06/04/2017 at 18:45:39 +0100, Ben Hutchings wrote: > On Thu, 2017-04-06 at 10:38 +0200, Greg Kroah-Hartman wrote: > > 4.4-stable review patch. If anyone has any objections, please let me know. > > > > ------------------ > > > > From: Alexandre Belloni > > > > commit 0b0408745e7ff24757cbfd571d69026c0ddb803c upstream. > > > > LPDDR memories can only handle up to 400 uncontrolled power off. Ensure the > > proper power off sequence is used before shutting down the platform. > > > > Signed-off-by: Alexandre Belloni > > Signed-off-by: Sebastian Reichel > > Signed-off-by: Greg Kroah-Hartman > [...] > > +static void at91_lpddr_poweroff(void) > > +{ > > + asm volatile( > > + /* Align to cache lines */ > > + ".balign 32\n\t" > > + > > + /* Ensure AT91_SHDW_CR is in the TLB by reading it */ > > + " ldr r6, [%2, #" __stringify(AT91_SHDW_CR) "]\n\t" > > This clobbers r6... > > > + /* Power down SDRAM0 */ > > + " str %1, [%0, #" __stringify(AT91_DDRSDRC_LPR) "]\n\t" > > + /* Shutdown CPU */ > > + " str %3, [%2, #" __stringify(AT91_SHDW_CR) "]\n\t" > > + > > + " b .\n\t" > > + : > > + : "r" (mpddrc_base), > > + "r" cpu_to_le32(AT91_DDRSDRC_LPDDR2_PWOFF), > > + "r" (at91_shdwc_base), > > + "r" cpu_to_le32(AT91_SHDW_KEY | AT91_SHDW_SHDW) > > + : "r0"); > [...] > > ...but the clobber list has r0. > Indeed. However, It doesn't matter much as nothing can possibly run afterwards. -- Alexandre Belloni, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com