Re: Designware MSHC: dw_mmc versus sdhci-of-dwcmshc?

[Jisheng Zhang <jszhang@kernel.org>]

On Sat, Aug 27, 2022 at 01:07:16PM -0700, Drew Fustini wrote:
> Hello, I am bringing up Linux on an SoC which has Synopsys "DesignWare

Hi Drew,

> Cores Mobile Storage Host Controller (Cryptographic)" IP configured to
> support an eMMC 5.0 device (IS21ES08G) on the bring-up board. I am
> trying to figure out why there are two seemingly similar drivers,
> dw_mmc and sdhci-of-dwmshc, in drivers/mmc/host for Synopsys
> DesignWare host controller IP. I am hoping someone might be able to
> give me some insight into the history of these drivers.

Generally speaking, dw_mmc isn't sdhci compatible while the
sdhci-of-dwmshc is sdhci compatible. Those two are for two different
controllers.

Regards
> 
> I have found the following:
> 
> - dw_mmc.c is a "DW Multimedia Card Interface driver"
> - created back in 2011 with f95f3850f7a9 ("mmc: dw_mmc: Add Synopsys
> DesignWare mmc host driver.")
> - CONFIG_MMC_DW  refers to it as "Synopsys DesignWare Memory Card
> Interface" with description of "Synopsys DesignWare Mobile Storage IP
> block, this provides host support for SD and MMC interfaces, in both
> PIO, internal DMA mode and external DMA mode"
> - "snps,dw-mshc" compatible supported in dw_mmc-pltfm.c and
> synopsys-dw-mshc.yaml binding refers to it as "Synopsys Designware
> Mobile Storage Host Controller"
> 
> - sdhci-of-dwcmshc.c is a "SDHCI platform driver for Synopsys DWC MSHC"
> - created more recently in 2018 with e438cf49b305 ("mmc:
> sdhci-of-dwcmshc: add SDHCI OF Synopsys DWC MSHC driver")
> - CONFIG_MMC_SDHCI_OF_DWCMSHC refers to it as "SDHCI OF support for
> the Synopsys DWC MSHC" with description of "Synopsys DesignWare Cores
> Mobile Storage Controller support."
> - the driver supports "snps,dwcmshc-sdhci" compatible and the
> snps,dwcmshc-sdhci.yaml binding describes it as "Synopsys Designware
> Mobile Storage Host Controller"
> 
> I would greatly appreciate any advice anyone may have on which driver
> might be the best fit.
> 
> Thank you,
> Drew