drivers/intel/fsp2_0: Add native implementation for FSP Debug Handler

This patch implements coreboot native debug handler to manage the FSP
event messages.

`FSP Event Handlers` feature introduced in FSP to generate event
messages to aid in the debugging of firmware issues. This eliminates
the need for FSP to directly write debug messages to the UART and FSP
might not need to know the board related UART port configuration.
Instead FSP signals the bootloader to inform it of a new debug message.
This allows the coreboot to provide board specific methods of reporting
debug messages, example: legacy UART or LPSS UART etc.

This implementation has several advantages as:
1. FSP relies on XIP `DebugLib` driver even while printing FSP-S debug
   messages, hence, without ROM being cached, post `romstage` would
   results into sluggish boot with FSP debug enabled.

   This patch utilities coreboot native debug implementation which is
   XIP during FSP-M and relocatable to DRAM based resource for FSP-S.

2. This patch simplifies the FSP DebugLib implementation and remove the
   need to have serial port library. Instead coreboot `printk` can be
   used for display FSP serial messages. Additionally, unifies the debug
   library between coreboot and FSP.

3. This patch is also useful to get debug prints even with FSP
   non-serial image (refer to `Note` below) as FSP PEIMs are now
   leveraging coreboot debug library instead FSP `NULL` DebugLib
   reference for release build.

4. Can optimize the FSP binary size by removing the DebugLib dependency
   from most of FSP PEIMs, for example: on Alder Lake FSP-M debug binary
   size is reduced by ~100KB+ and FSP-S debug library size is also
   reduced by ~300KB+ (FSP-S debug and release binary size is exactly
   same with this code changes). The total savings is ~400KB for each
   FSP copy, and in case of Chrome AP firmware with 3 copies, the total
   savings would be 400KB * 3 = ~1.2MB.

Note: Need to modify FSP source code to remove `MDEPKG_NDEBUG` as
compilation flag for release build and generate FSP binary with non-NULL
FSP debug wrapper module injected (to allow FSP event handler to execute
even with FSP non-serial image) in the final FSP.fd.

BUG=b:225544587
TEST=Able to build and boot brya. Also, verified the FSP debug log is
exactly same before and with this code change.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: I1018e67d70492b18c76531f9e78d3b58fa435cd4
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63007
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

0 files changed, 0 insertions, 0 deletions