[U-Boot] [PATCH v2 06/10] powerpc/ppc4xx: Use generic FPGA accessors on all gdsys 405ep/ex boards

[Dirk Eibach <dirk.eibach@gdsys.cc>]

Hi Wolfgang,

in my example we have four FPGAs. One is memory mapped while the other 
three are not.
They all have the same register interface which is mapped by
   struct ihs_fpga {
	u16 reflection_low;
	u16 versions;
	...
	u16 mc_tx_address;
	u16 mc_tx_data;
	u16 mc_tx_cmd;
	...
   };

To have instances of those FPGA structs, we might create an array like 
this:
   struct ihs_fpga system_fpgas[] = {
	(struct ihs_fpga *)CONFIG_SYS_FPGA_BASE,
	(struct ihs_fpga *)NULL,
	(struct ihs_fpga *)NULL,
	(struct ihs_fpga *)NULL,
   };
The first element ist our memory mapped FPGA with base address 
CONFIG_SYS_FPGA_BASE. For the other three I use NULL as base address 
because I don't have any better idea what else to choose.

To probe those FPGAs we might have to do something like:
   for (k=0; k < 4; ++k)
	fpga_set_reg(k, &system_fpgas[k].reflection_low, 
REFLECTION_TESTPATTERN);

The implementation of fpga_set_reg() might look like:

void fpga_set_reg(unsigned int fpga, u16 *reg, u16 data)
{
	switch (fpga) {
	case 0:
		out_le16(reg, data);
		break;
	default:
		mclink_send(fpga - 1, (u16)reg, data);
		break;
	}
}

where mclink_send() is the routine to access the non memory mapped 
FPGAs through the memory mapped FPGA:
   int mclink_send(u8 slave, u16 addr, u16 data)
   {
	...
	fpga_set_reg(0, &system_fpgas[0].mc_tx_address, addr);
	fpga_set_reg(0, &system_fpgas[0].mc_tx_data, data);
	fpga_set_reg(0, &system_fpgas[0].mc_tx_cmd, (slave & 0x03) << 14);
   }

The cast to u16 I am talking about happens, when mclink_send() is 
called.

Cheers
Dirk