Change in coreboot[master]: intel/xeon_sp, mb/ocp/deltalake: Rework get_stack_busnos()

[Angel Pons (Code Review)]

Attention is currently required from: Anjaneya "Reddy" Chagam, Maxim Polyakov, Morgan Jang.
Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/49457 )

Change subject: intel/xeon_sp, mb/ocp/deltalake: Rework get_stack_busnos()
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Patch Set 4:

(2 comments)

File src/soc/intel/xeon_sp/util.c:

https://review.coreboot.org/c/coreboot/+/49457/comment/925f301e_77ba69c6 
PS4, Line 18: get_stack_busnos
As this function now provides one bus number, remove the plural `s`: `get_stack_busno`

https://review.coreboot.org/c/coreboot/+/49457/comment/30de17c5_0a32aedf 
PS4, Line 19: {
            : 	uint32_t reg;
            : 	uint8_t  busno = 0;
            : 	if (stack >= MAX_IIO_STACK) {
            : 		printk(BIOS_ERR, "%s:%s Stack %d does not exist!\n", __FILE__, __func__, stack);
            : 	} else if (stack >= 4) {
            : 		reg = pci_mmio_read_config32(PCI_DEV(UBOX_DECS_BUS, UBOX_DECS_DEV,
            : 			UBOX_DECS_FUNC), UBOX_DECS_CPUBUSNO1_CSR);
            : 		busno = BUSNO(stack - 4, reg);
            : 	} else {
            : 		reg = pci_mmio_read_config32(PCI_DEV(UBOX_DECS_BUS, UBOX_DECS_DEV,
            : 			UBOX_DECS_FUNC), UBOX_DECS_CPUBUSNO_CSR);
            : 		busno = BUSNO(stack, reg);
            : 	}
            : 	return busno;
            : }
Since the register definitions are orthogonal, this can be simplified a bit:

{
    if (stack >= MAX_IIO_STACK) {
    	printk(BIOS_ERR, "%s: Stack %u does not exist!\n", __func__, stack);
    	return 0;
    }
    const pci_devfn_t dev = PCI_DEV(UBOX_DECS_BUS, UBOX_DECS_DEV, UBOX_DECS_FUNC);
    const uint32_t reg32 = pci_io_read_config32(dev, UBOX_DECS_CPUBUSNO_CSR + stack / 4);
    return (reg32 >> (8 * (stack % 4)) & 0xff;
 }

Yes, this doesn't use any of the definitions that the previous patch adds. I find it's clearer this way.