lkml.org 
[lkml]   [2022]   [Aug]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 1/3] dt-bindings: spi: stm32: Add st,dual-flash property in st,stm32-qspi.yaml
From


On 8/9/22 09:57, Krzysztof Kozlowski wrote:
> On 09/08/2022 10:52, Patrice CHOTARD wrote:
>> Hi Krzystof
>>
>> On 8/9/22 07:29, Krzysztof Kozlowski wrote:
>>> On 09/08/2022 07:18, Krzysztof Kozlowski wrote:
>>>> On 08/08/2022 19:08, Patrice CHOTARD wrote:
>>>>> Hi Krzystof
>>>>>
>>>>> On 8/8/22 11:01, Krzysztof Kozlowski wrote:
>>>>>> On 08/08/2022 10:40, patrice.chotard@foss.st.com wrote:
>>>>>>> From: Patrice Chotard <patrice.chotard@foss.st.com>
>>>>>>>
>>>>>>> Add new property st,dual-flash which allows to use the QSPI interface as a
>>>>>>> communication channel using up to 8 qspi line.
>>>>>>> This mode can only be used if cs-gpios property is defined.
>>>>>>>
>>>>>>> Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
>>>>>>> ---
>>>>>>> Documentation/devicetree/bindings/spi/st,stm32-qspi.yaml | 8 ++++++++
>>>>>>> 1 file changed, 8 insertions(+)
>>>>>>>
>>>>>>> diff --git a/Documentation/devicetree/bindings/spi/st,stm32-qspi.yaml b/Documentation/devicetree/bindings/spi/st,stm32-qspi.yaml
>>>>>>> index 6ec6f556182f..5e4f9109799e 100644
>>>>>>> --- a/Documentation/devicetree/bindings/spi/st,stm32-qspi.yaml
>>>>>>> +++ b/Documentation/devicetree/bindings/spi/st,stm32-qspi.yaml
>>>>>>> @@ -46,6 +46,14 @@ properties:
>>>>>>> - const: tx
>>>>>>> - const: rx
>>>>>>>
>>>>>>> + st,dual-flash:
>>>>>>> + type: boolean
>>>>>>> + description:
>>>>>>> + Allows to use 8 data lines in case cs-gpios property is defined.
>>>>>>
>>>>>> It's named dual-flash, but what if you want to use QSPI to connect for
>>>>>> example to FPGA?
>>>>>>
>>>>>> Also how is this related to parallel-memories property?
>>>>>
>>>>> I called it "dual-flash" simply because it enable the dual flash feature of the QSPI block (bit CR_DFM : Dual Flash Mode)
>>>>> which allows to use the 8 lines simultaneously of our dual QSPI block.
>>>>
>>>> And how is it related to existing parallel-memories property?
>>>
>>> Maybe I was not specific enough, so let me rephrase - we have already
>>> parallel-memories property. How this one is different (to justify the
>>> new property)? Is just one memory connected in your case to QSPI over 8
>>> data lines?
>>
>> Our QSPI block is a dual Quad-SPI memory interface, it can managed 2 QSPI flashes independently.
>> There is a specific mode, dual flash mode, where the 2 QSPI flashes can be accessed simultaneously
>> using 8 data lines. In this case, both throughput and capacity are two fold with this mode.
>>
>> To illustrate, you can have a look at STM32MP157 reference manual (chapter 27.3.1 figure 172) available here:
>> https://www.st.com/resource/en/reference_manual/rm0436-stm32mp157-advanced-armbased-32bit-mpus-stmicroelectronics.pdf
>>
>> As you mentioned above, the goal is to connect a FPGA to this 8 lines bus.
>>
>> Hope it clarifies enough ;-)
>
> Only partially. Based on the explanation above, it looks like you want
> to use existing parallel-memories property. Please use that one, instead
> of adding a new property for the same feature.

Okay, got it, i didn't notice the parallel-memories property recently added.

Thanks for pointing it.
Patrice

>
> Best regards,
> Krzysztof

\
 
 \ /
  Last update: 2022-08-09 10:02    [W:0.045 / U:0.124 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site