Designware MSHC: dw_mmc versus sdhci-of-dwcmshc?

Designware MSHC: dw_mmc versus sdhci-of-dwcmshc?

[Drew Fustini]

Hello, I am bringing up Linux on an SoC which has Synopsys "DesignWare
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.

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

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

[Jisheng Zhang]

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