From 7f8afe063139f6fc7076a3e4edf6093a953792dc Mon Sep 17 00:00:00 2001 From: Aaron Durbin Date: Fri, 18 Mar 2016 12:21:23 -0500 Subject: arch/x86: introduce postcar stage/phase Certain chipsets don't have a memory-mapped boot media so their code execution for stages prior to DRAM initialization is backed by SRAM or cache-as-ram. The postcar stage/phase handles the cache-as-ram situation where in order to tear down cache-as-ram one needs to be executing out of a backing store that isn't transient. By current definition, cache-as-ram is volatile and tearing it down leads to its contents disappearing. Therefore provide a shim layer, postcar, that's loaded into memory and executed which does 2 things: 1. Tears down cache-as-ram with a chipset helper function. 2. Loads and runs ramstage. Because those 2 things are executed out of ram there's no issue of the code's backing store while executing the code that tears down cache-as-ram. The current implementation makes no assumption regarding cacheability of the DRAM itself. If the chipset code wishes to cache DRAM for loading of the postcar stage/phase then it's also up to the chipset to handle any coherency issues pertaining to cache-as-ram destruction. Change-Id: Ia58efdadd0b48f20cfe7de2f49ab462306c3a19b Signed-off-by: Aaron Durbin Reviewed-on: https://review.coreboot.org/14140 Tested-by: build bot (Jenkins) Reviewed-by: Patrick Georgi Reviewed-by: Furquan Shaikh --- src/arch/x86/memlayout.ld | 2 ++ 1 file changed, 2 insertions(+) (limited to 'src/arch/x86/memlayout.ld') diff --git a/src/arch/x86/memlayout.ld b/src/arch/x86/memlayout.ld index 5661104179..e6db0b8fe6 100644 --- a/src/arch/x86/memlayout.ld +++ b/src/arch/x86/memlayout.ld @@ -51,6 +51,8 @@ SECTIONS /* Pull in the cache-as-ram rules. */ #include "car.ld" +#elif ENV_POSTCAR + POSTCAR(32M, 1M) #endif } -- cgit v1.2.3