linux-kernel - Re: [PATCH v1 0/2] spi: cadence-qspi: Add cadence-qspi support for Intel LGM SoC

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Date:   Thu, 10 Oct 2019 13:08:58 +0800
From:   "Ramuthevar, Vadivel MuruganX" 
        <vadivel.muruganx.ramuthevar@...ux.intel.com>
To:     Vignesh Raghavendra <vigneshr@...com>, broonie@...nel.org
Cc:     robh+dt@...nel.org, mark.rutland@....com,
        linux-spi@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, cheol.yong.kim@...el.com,
        qi-ming.wu@...el.com
Subject: Re: [PATCH v1 0/2] spi: cadence-qspi: Add cadence-qspi support for
 Intel LGM SoC

Hi Vignesh,

On 10/10/2019 12:18 PM, Vignesh Raghavendra wrote:
>
> On 10/10/19 7:04 AM, Ramuthevar, Vadivel MuruganX wrote:
>> HI Vignesh,
>>
>> On 17/9/2019 12:50 AM, Vignesh Raghavendra wrote:
>>> Hi,
>>>
>>> On 16/09/19 1:08 PM, Ramuthevar,Vadivel MuruganX wrote:
>>>> patch 1: Add YAML for cadence-qspi devicetree cdocumentation.
>>>> patch 2: cadence-qspi controller driver to support QSPI-NAND flash
>>>> using existing spi-nand framework with legacy spi protocol.
>>> Nope, you cannot have two drivers for the same IP (i.e Cadence QSPI)
>>> just to support to different types of SPI memories. This is the reason
>>> why spi_mem_ops was introduced.
>>>
>>> Please rewrite this driver over to use spi_mem_ops (instead of using
>>> generic SPI xfers) so that same driver supports both SPI-NOR and
>>> SPI-NAND flashes. Once that's done drivers/mtd/spi-nor/cadence-quadspi.c
>>> can be deleted.
>>>
>>> There are few existing examples of spi_mem_ops users in drivers/spi/
>>> (git grep spi_mem_ops) and materials here on how to write such a driver:
>>>
>>> [1]
>>> https://bootlin.com/blog/spi-mem-bringing-some-consistency-to-the-spi-memory-ecosystem/
>>>
>>> [2] https://www.youtube.com/watch?v=PkWbuLM_gmU
>> As per Mark Brown and your suggestion,  I have started adapting
>> cadence-qaudspi driver with spi_mem_ops framework to work
>> QSPI-NAND/NOR as a generic driver(completely removed the legacy
>> SPI-XFERS),  is in progress on Intel LGM SoC.
>> QSPI-IP on Intel LGM  do not have DMA  support and also not part of QSPI
>> IP, so couldn't able to validate DMA related.
>> will adapt the DMA things which are existing in cadence-quadspi.c as it is.
>>
> Great, appreciate the effort!
>
>> currently TI and Altera SoC's use this Cadence-qspi IP , both are not
>> using DMA as per my understanding (correct me if it is wrong).
>> confirmed through device tree entry.
>>
> TI platforms use DMA to read data from flash in memory mapped mode
> (direct access controller) using mem-to-mem DMA channels. Mem-to-mem DMA
> channels are requested as and when needed and are not part of DT
> description (as they are not bound to a device)
yes, understood now, Thanks!
>> what is your opinion on DMA related stuff?
> Not having DMA support would be a regression. Please keep the DAC + DMA
> part as is. I can help you will all the DMA related testing...
Sure, will keep DAC + DMA, as we discussed earlier use QUIRKS to 
differentiate and follow the same.

---
With Regards
Vadivel

> Regards
> Vignesh
>
>> also using macronix(QSPI-NOR)
>> flash/Micron(QSPI-NAND).
>> ---
>> With Regards
>> Vadivel
>>>> Ramuthevar Vadivel Murugan (2):
>>>>     dt-bindings: spi: Add support for cadence-qspi IP Intel LGM SoC
>>>>     spi: cadence-qspi: Add QSPI support for Intel LGM SoC
>>>>
>>>>    .../devicetree/bindings/spi/cadence,qspi-nand.yaml |  84 +++
>>>>    drivers/spi/Kconfig                                |   9 +
>>>>    drivers/spi/Makefile                               |   1 +
>>>>    drivers/spi/spi-cadence-qspi-apb.c                 | 644
>>>> +++++++++++++++++++++
>>>>    drivers/spi/spi-cadence-qspi-apb.h                 | 174 ++++++
>>>>    drivers/spi/spi-cadence-qspi.c                     | 461
>>>> +++++++++++++++
>>>>    drivers/spi/spi-cadence-qspi.h                     |  73 +++
>>>>    7 files changed, 1446 insertions(+)
>>>>    create mode 100644
>>>> Documentation/devicetree/bindings/spi/cadence,qspi-nand.yaml
>>>>    create mode 100644 drivers/spi/spi-cadence-qspi-apb.c
>>>>    create mode 100644 drivers/spi/spi-cadence-qspi-apb.h
>>>>    create mode 100644 drivers/spi/spi-cadence-qspi.c
>>>>    create mode 100644 drivers/spi/spi-cadence-qspi.h
>>>>