[XS] Change in coreboot[main]: intel/cmm/block: use CONFIG_SMM_TSEG_SIZE in sa_get_tseg_size function

[Subrata Banik (Code Review)]

Attention is currently required from: Anil Kumar K, Bora Guvendik, Jamie Ryu, Jeremy Compostella, Jérémy Compostella, Paul Menzel, Wonkyu Kim.

Subrata Banik has posted comments on this change by Wonkyu Kim. ( https://review.coreboot.org/c/coreboot/+/84210?usp=email )

Change subject: intel/cmm/block: use CONFIG_SMM_TSEG_SIZE in sa_get_tseg_size function
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Patch Set 3:

(2 comments)

File src/soc/intel/common/block/systemagent/systemagent_early.c:

https://review.coreboot.org/c/coreboot/+/84210/comment/8612df26_319ca45f?usp... :
PS2, Line 155: 	return sa_get_gsm_base() - sa_get_tseg_base();
> FSP team mentioned that Tseg size is passed by UPD and memory map(relationship for  Tesg base and gsm base) can also be changed in future silicon.  So, FSP team recommend use Tseg size which is passed to UPD which is CONFIG_SMM_TSEG_SIZE.

Sorry, unable to follow why we need to adhere to the FSP team recommendation when we know what is the correct way to calculate the Tseg size. I hear your problem and suggested a better path to check GSM size to know if IGD exists. Am I missing anything ?

File src/soc/intel/common/block/systemagent/systemagent_early.c:

https://review.coreboot.org/c/coreboot/+/84210/comment/a46c5385_5bf6c802?usp... :
PS3, Line 151: 	if (CONFIG_SMM_TSEG_SIZE) {
             : 		return CONFIG_SMM_TSEG_SIZE;
             : 	}
             :
> If CONFIG_SMM_TSEG_SIZE is defined use CONFIG_SMM_TSEG_SIZE rather than calculation.

i'm unable to follow the problem of calculating the exact value using `GSM base - TSEG size` to calculate the actual value (reading from HW register) rather relying on static config. what if some floor/ceiling adjustment has been made over CONFIG_SMM_TSEG_SIZE to define the alignment? in such case relying on CONFIG_SMM_TSEG_SIZE won't be appropriate