From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH 05/10] ARM: dt: tegra: add bindings of power management configurations for PMC Date: Mon, 11 Mar 2013 14:51:37 -0600 Message-ID: <513E43D9.9060109@wwwdotorg.org> References: <1362397241-5786-1-git-send-email-josephl@nvidia.com> <51363F67.8040200@wwwdotorg.org> <1362654973.1890.28.camel@jlo-ubuntu-64.nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1362654973.1890.28.camel-yx3yKKdKkHfc7b1ADBJPm0n48jw8i0AO@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Joseph Lo Cc: Bo Yan , Peter De Schrijver , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" , Grant Likely , Rob Herring , "devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" List-Id: linux-tegra@vger.kernel.org On 03/07/2013 04:16 AM, Joseph Lo wrote: > On Wed, 2013-03-06 at 02:54 +0800, Stephen Warren wrote: >> On 03/04/2013 04:40 AM, Joseph Lo wrote: >>> The PMC mostly controls the entry and exit of the system from different >>> sleep modes. Different platform or system may have different configurations. >>> The power management configurations of PMC is represented as some properties. >>> The system needs to define the properties when the system supports deep sleep >>> mode (i.e. suspend). >> >> One overall question here: For LP0, the idea is that the bootloader >> provides the AVP boot code, puts it in RAM, passes the address to the >> kernel, which then arranges for that code to be executed when the system >> resumes from LP0. Why does the bootloader have to provide the code? Why >> can't the AVP code simply be part of the kernel, just like e.g. the main >> CPU's hotplug/secondary-power-on/power-saving reset vector is part of >> the kernel? If we did that, it'd remove any need for bootloader support >> for LP0 - the kernel would manage it entirely internally. That seems >> much simpler. > > Yes, I had exactly the same question before. I think the downstream discussion we had concluded that we need to keep doing this, so we do need the lp0-vec property in DT. The reason is that LP0 vector code is sometimes encrypted, and the kernel can't perform that encryption, and hence can't provide the code itself - the code must be given to the kernel.