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In-Reply-To: <CAHf5cscRkiCHw9HmJncTuA9E1dZDmEYTvkhkH4dF-nZcpEDnaA@mail.gmail.com>
From: "Milton Miller II" <miltonm@us.ibm.com>
To: VINOTHKUMAR RK <vkrk.user@gmail.com>
Date: Mon, 19 Jul 2021 16:32:10 +0000
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Subject: Re:  AST2600: Linux driver support for SPI controller
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On July 19, 2021,  VINOTHKUMAR RK wrote:
>Hello all,
>
>This is regarding SPI controller driver support in OpenBMC.
>Here is the scenario: Three devices connected over same SPI
>controller as mentioned below:
>
>Firmware SPI Memory Controller (BSPI): (0x1E620000):
>    - Flash 0 (CS0)
>    - Flash 1 (CS1)
>    - MCU/CPLD (CS2)
>
>When I look at the OpenBMC Linux repository, I could find
>'aspeed-smc.c' driver under the MTD subsystem, so this seems to work
>only for flash devices.
>
>Do we've any other driver support or a solution to handle all the
>three devices? Any help/suggestions would be appreciated.

I was involved with the driver you found before Cedric took it=20
over.

I am not aware of anyone writing a generic SPI acccess driver.  =20
The hardwaredoes have a user mode that does not auto-sequence, but=20
as I remember its limited in that it can not read and write data=20
at the same time and is limited to transfers that are multiples of=20
a byte.

If your MCU/CPLD can live with these limitations then you or=20
someone can integrate a spi layer driver into the current=20
driver.

Note on the 2600 the hardware for the host is the same as the=20
hardware for the BMC.  It may be easier to develop spi mode on=20
that port because it could be developed while running with the=20
BMC from existing driver.  Alternatively it could be developed=20
on a system that runs on eMMC.

Milton