diff options
| -rw-r--r-- | src/soc/intel/common/basecode/ramtop/ramtop.c | 30 |
1 files changed, 12 insertions, 18 deletions
diff --git a/src/soc/intel/common/basecode/ramtop/ramtop.c b/src/soc/intel/common/basecode/ramtop/ramtop.c index 0ef531acb0..203d3437c7 100644 --- a/src/soc/intel/common/basecode/ramtop/ramtop.c +++ b/src/soc/intel/common/basecode/ramtop/ramtop.c @@ -181,25 +181,19 @@ void early_ramtop_enable_cache_range(void) } size_t ramtop_size = get_ramtop_size(); + if (!ramtop_size) + return; + /* - * Background: Some SoCs have a critical bug inside the NEM logic which is responsible - * for mapping cached memory to physical memory during tear down and - * eventually malfunctions if the number of cache sets is not a power of two. - * This can lead to runtime hangs. + * INTEL RECOMMENDATION: Early Ramtop Caching Configuration * - * Workaround: To mitigate this issue on affected SoCs, we force the MTRR type to - * WC (Write Combining) unless the cache set count is a power of two. - * This change alters caching behavior but prevents the runtime failures. + * Configuring the Early Caching Ramtop range as Write-Back (WB) before + * memory initialization is NOT RECOMMENDED. Speculative execution within + * this WB range can lead to issues. WB configuration should be applied + * to this range ONLY AFTER memory initialization is complete. + * + * To enable Ramtop caching before memory initialization, use Write-Combining + * (WC) instead of Write-Back (WB). */ - unsigned int mtrr_type = MTRR_TYPE_WRCOMB; - /* - * Late romstage (including FSP-M post-memory initialization) needs to be - * executed from cache for performance reasons. This requires caching - * `ramtop_size`, which encompasses both FSP reserved memory and the CBMEM - * range, to guarantee sufficient cache coverage for late romstage. - */ - if (is_cache_sets_power_of_two()) - mtrr_type = MTRR_TYPE_WRBACK; - - set_var_mtrr(mtrr, ramtop - ramtop_size, ramtop_size, mtrr_type); + set_var_mtrr(mtrr, ramtop - ramtop_size, ramtop_size, MTRR_TYPE_WRCOMB); } |