[S] Change in coreboot[main]: mb/google/rex/var/rex: Configure PL4 to 64W if battery status is invalid

[Subrata Banik (Code Review)]

Attention is currently required from: Brandon Breitenstein, Caveh Jalali, Eran Mitrani, Hannah Williams, Jamie Ryu, Kapil Porwal, Sukumar Ghorai, Tarun.

Subrata Banik has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/78322?usp=email )

Change subject: mb/google/rex/var/rex: Configure PL4 to 64W if battery status is invalid
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Patch Set 5:

(4 comments)

File src/mainboard/google/rex/variants/baseboard/rex/ramstage.c:

https://review.coreboot.org/c/coreboot/+/78322/comment/b9f72708_08ab35d9 :
PS5, Line 13: limits
rename this to `performance_efficient_limits`` in one CL

https://review.coreboot.org/c/coreboot/+/78322/comment/bbb5bfa2_d13a1b84 :
PS5, Line 25: p
what is lp ? low_power ?

nit: `power_optimized_limits`

https://review.coreboot.org/c/coreboot/+/78322/comment/09554a2b_3c7e77ae :
PS5, Line 41: google_chromeec_read_battery_status
shouldn't this be < 0 ??

btw, how does google_chromeec_read_battery_status() functionality help you to take the correct decision ?

I assume, what u need is an API to tell you to override PL4 limits if no battery present or dead battery should it named as `google_chromeec_is_battery_enabled()`

``` 
struct cpu_tdp_power_limits *limits = performance_efficient_limits;
size_t limits_size = ARRAY_SIZE(performance_efficient_limits);

if (google_chromeec_is_battery_enabled(&battery_status) == 0) {
    limits = power_optimized_limits;
    limits_size = ARRAY_SIZE(power_optimized_limits);
}

variant_update_cpu_power_limits(imits, ARRAY_SIZE(limits_size));

```

https://review.coreboot.org/c/coreboot/+/78322/comment/96b8716f_d38e4fae :
PS5, Line 42: 		printk(BIOS_ERR, "Failed to read EC battery info\n");
what is the fallback when battery info check is failing ? just continue ?