Re: [PATCH v3 2/3] spi: dt-bindings: Describe stacked/parallel memories modes

Tudor.Ambarus
2021-12-07T07:44:35Z

On 12/7/21 9:35 AM, Tudor Ambarus wrote:
> On 12/7/21 9:14 AM, Pratyush Yadav wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
>>
>> On 06/12/21 10:59AM, Miquel Raynal wrote:
>>> Describe two new memories modes:
>>> - A stacked mode when the bus is common but the address space extended
>>> with an additinals wires.
>>> - A parallel mode with parallel busses accessing parallel flashes where
>>> the data is spread.
>>>
>>> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
>>> ---
>>> .../bindings/spi/spi-peripheral-props.yaml | 21 +++++++++++++++++++
>>> 1 file changed, 21 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
>>> index 5dd209206e88..13aa6a2374c9 100644
>>> --- a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
>>> +++ b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
>>> @@ -82,6 +82,27 @@ properties:
>>> description:
>>> Delay, in microseconds, after a write transfer.
>>>
>>> + stacked-memories:
>>> + type: boolean
>>
>> I don't think a boolean is enough to completely describe the memory.
>> Sure, you say the memories are stacked, but where do you specify when to
>> switch the CS? They could be two 512 MiB memories, two 1 GiB memories,
>> or one 512 MiB and one 256 MiB.
>
> If the multi-die flash contains identical dies then the die boundary can be
> determined with flash_size / number_of_cs. Are there any multi die flashes

but the problem is there, yes, there is still the case where there are stacked
devices with a single cs. We'll need to describe the size of the die in some
way.