hw/dma: sifive_pdma: support high 32-bit access of 64-bit register

hw/dma: sifive_pdma: support high 32-bit access of 64-bit register

Real PDMA supports high 32-bit read/write memory access of 64-bit
register.

The following result is PDMA tested in U-Boot on Unmatched board:

1. Real PDMA allows high 32-bit read/write to 64-bit register.
=> mw.l 0x3000000 0x0                      <= Disclaim channel 0
=> mw.l 0x3000000 0x1                      <= Claim channel 0
=> mw.l 0x3000010 0x80000000               <= Write low 32-bit NextDest (NextDest = 0x280000000)
=> mw.l 0x3000014 0x2                      <= Write high 32-bit NextDest
=> md.l 0x3000010 1                        <= Dump low 32-bit NextDest
03000010: 80000000
=> md.l 0x3000014 1                        <= Dump high 32-bit NextDest
03000014: 00000002
=> mw.l 0x3000018 0x80001000               <= Write low 32-bit NextSrc (NextSrc = 0x280001000)
=> mw.l 0x300001c 0x2                      <= Write high 32-bit NextSrc
=> md.l 0x3000018 1                        <= Dump low 32-bit NextSrc
03000010: 80001000
=> md.l 0x300001c 1                        <= Dump high 32-bit NextSrc
03000014: 00000002

2. PDMA transfer from 0x280001000 to 0x280000000 is OK.
=> mw.q 0x3000008 0x4                      <= NextBytes = 4
=> mw.l 0x3000004 0x22000000               <= wsize = rsize = 2 (2^2 = 4 bytes)
=> mw.l 0x280000000 0x87654321             <= Fill test data to dst
=> mw.l 0x280001000 0x12345678             <= Fill test data to src
=> md.l 0x280000000 1; md.l 0x280001000 1  <= Dump src/dst memory contents
280000000: 87654321                              !Ce.
280001000: 12345678                              xV4.
=> md.l 0x3000000 8                        <= Dump PDMA status
03000000: 00000001 22000000 00000004 00000000    ......."........
03000010: 80000000 00000002 80001000 00000002    ................
=> mw.l 0x3000000 0x3                      <= Set channel 0 run and claim bits
=> md.l 0x3000000 8                        <= Dump PDMA status
03000000: 40000001 22000000 00000004 00000000    ...@..."........
03000010: 80000000 00000002 80001000 00000002    ................
=> md.l 0x280000000 1; md.l 0x280001000 1  <= Dump src/dst memory contents
280000000: 12345678                               xV4.
280001000: 12345678                               xV4.

Signed-off-by: Jim Shu <jim.shu@sifive.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Message-id: 20220104063408.658169-2-jim.shu@sifive.com
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>