60 lines
1.9 KiB
Plaintext
60 lines
1.9 KiB
Plaintext
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SPI NOR framework
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============================================
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Part I - why we need this framework?
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-------------------------------------
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The SPI bus controller only deals with the byte stream.
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Some controller does not works like a SPI bus controller, it works
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like a SPI NOR controller instead, such as the Freescale's QuadSPI controller.
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The Freescale's QuadSPI controller should know the NOR commands to
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find the right LUT sequence. Unfortunately, the old code can not meet
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this requirement.
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Part II - How does the framework work?
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-------------------------------------
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This framework just adds a new layer between the MTD and the SPI bus driver.
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With this new layer, the SPI NOR controller driver does not depend on the
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m25p80 code anymore.
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Before this framework, the layer is like:
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MTD
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------------------------
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m25p80
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------------------------
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SPI bus driver
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------------------------
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SPI NOR chip
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After this framework, the layer is like:
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MTD
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------------------------
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SPI NOR framework
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------------------------
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m25p80
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------------------------
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SPI bus driver
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------------------------
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SPI NOR chip
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With the SPI NOR controller driver(Freescale QuadSPI), it looks like:
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MTD
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------------------------
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SPI NOR framework
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------------------------
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fsl-quadSPI
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------------------------
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SPI NOR chip
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Part III - How can the drivers use the framework
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-------------------------------------
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The main API is the spi_nor_scan(). Before you call the hook, you should
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initialize the necessary fields for spi_nor{}.
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Please see the drivers/mtd/spi-nor/spi-nor.c for detail.
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Please also reference to the fsl-quadspi.c when you want to write a new driver
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for a SPI NOR controller.
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