Re: [PATCH] mtd: nand: denali: allow to override max_banks from DT property
From: Masahiro Yamada
Date: Sat Mar 26 2016 - 00:28:17 EST
2016-03-25 23:45 GMT+09:00 Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx>:
> On Thu, 24 Mar 2016 21:24:37 +0900
> Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx> wrote:
>> Commit 271707b1d817 ("mtd: nand: denali: max_banks calculation
>> changed in revision 5.1") supported the new encoding of the "n_banks"
>> bits of the "features" register, but there is an unfortunate case
>> that is not covered by that commit.
>> Panasonic (its System LSI division is now Socionext) bought several
>> versions of this IP. The IP released for Panasonic around Feb. 2012
>> is revision 5 and uses the old encoding for n_banks (2 << n_banks).
>> While the one released around Nov. 2012 is also revision 5, but it
>> uses the new encoding (1 << n_banks).
>> The revision register cannot distinguish these two incompatible
>> hardware. I guess this IP series is not well-organized. I could not
>> find any alternative but giving max_banks from DT property.
> Hm, shouldn't that be addressed with a new compatible instead of adding
> a extra property?
>> This commit works around the problem by allowing DT to set the
>> max_banks forcibly. Of course, this DT property can be optional if
>> the auto detection based on the hardware registers works well.
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
>> Documentation/devicetree/bindings/mtd/denali-nand.txt | 4 ++++
>> drivers/mtd/nand/denali.c | 3 ++-
>> drivers/mtd/nand/denali_dt.c | 3 +++
>> 3 files changed, 9 insertions(+), 1 deletion(-)
>> diff --git a/Documentation/devicetree/bindings/mtd/denali-nand.txt b/Documentation/devicetree/bindings/mtd/denali-nand.txt
>> index 785b825..78c250d 100644
>> --- a/Documentation/devicetree/bindings/mtd/denali-nand.txt
>> +++ b/Documentation/devicetree/bindings/mtd/denali-nand.txt
>> @@ -7,6 +7,10 @@ Required properties:
>> - interrupts : The interrupt number.
>> - dma-mask : DMA bit mask
>> +Optional properties:
>> + - max-banks : Maximum number of banks supported by hardware. If not
>> + specified, it is determined based on the "features" register of hardware.
> You might want to prefix that with "denali,".
>> The device tree may optionally contain sub-nodes describing partitions of the
>> address space. See partition.txt for more detail.
In which case, do we have to add a vendor prefix to DT properties?
I do not know a clear rule about this.