Re: [PATCH] dt-bindings: nand: denali: reduce the register space in the example

From: Masahiro Yamada
Date: Thu Sep 21 2017 - 01:27:59 EST


2017-09-14 18:06 GMT+09:00 Oleksij Rempel <ore@xxxxxxxxxxxxxx>:
> On 14.09.2017 10:16, Masahiro Yamada wrote:
>> Hi.
>> 2017-09-14 17:04 GMT+09:00 Oleksij Rempel <ore@xxxxxxxxxxxxxx>:
>>> Hi,
>>> i assume arch/arm/boot/dts/socfpga.dtsi should be update as well. Right?
>> I think so.
>> (also arch/arm/boot/dts/socfpga_arria10.dtsi in the same way)
> Hm.. according to
> Table 13-18: NAND Controller Module Data Space Address Range
> Module Instance Start Address End Address
> So <0xff900000 0x100000> seems to be a proper value.

The Alrera's SOCFPGA document describes so.
It is up to each SoC vendor how to describe the register space.

I am focusing on the Denali IP
because this IP is used among several SoCs.

You can see the peripheral region map
starting at page 1-18 of the document you referred to:

Slave ID Description Base Addr Size
L3REGS L3 interconnect GPV 0xFF800000 1 MB
NANDDATA NAND flash controller data 0xFF900000 64 KB
QSPIDATA Quad SPI flash data 0xFFA00000 1 MB

(In the doc, the base is described as 0xFFB900000, but this is
apparently a typo.)

The rationale of the "End Address 0xFF9FFFFF" of NAND_DATA
is the fact that the base address of the next peripheral (QSPIDATA) is

One more, if you look at the next page,

Slave ID Description Base Addr Size
NANDREGS NAND flash controller registers 0xFFB80000 64 KB
FPGAMGRDATA FPGA manager configuration data 0xFFB90000 4 KB

The size of NAND register space is described as 64KB,
but the rationale is just the start of the next peripheral is 0xFFB90000.

(0xFFB90000 - 0xFFB80000 = 0x10000 = 64KB)

Altera apparently reserved address space just for the purpose
of matching the end address to the base address of the next peripheral.

That means, this document specifies address region
much bigger than the IP actually provides.

If you look at page 13-6, there are only two registers
in NANDDATA space.

Table 13-4: Register Map for Indexed Addressing
Control 0x0
Data 0x10

For NANDREGS, in page 13-106, the following is the last register
in the NANDREGS space.

Offset 0x7A0

Obviously, 0x1000 (4KB) is enough for NANDREGS.

To conclude this, this binding document was written
based on the Altera's SOCFPGA specification.

Altera specifies the region size
so that end address matches to the base of the next peripheral.
This is just a matter of SOCFPGA address mapping.

In my opinion, the binding document should not be oriented
to a particular SoC, which is not true for other SoCs.

Best Regards
Masahiro Yamada