Re: [PATCH v2] mmc: dw_mmc: Add external dma interface support

[Shawn Lin]

On 2015/8/3 19:17, Heiko Stübner wrote:
> Hi Shawn,
>
> Am Montag, 3. August 2015, 11:27:19 schrieb Shawn Lin:
> > DesignWare MMC Controller can support two types of DMA
> > mode: external dma and internal dma. We get a RK312x platform
> > integrated dw_mmc and ARM pl330 dma controller. This patch add
> > edmac ops to suuport these platforms. I've tested it on RK312x
> > platform with edmac mode and RK3288 platform with idmac mode.
> >
> > Patch is based on next of git://git.linaro.org/people/ulf.hansson/mmc
> >
> > Signed-off-by: Shawn Lin <shawn.lin@xxxxxxxxxxxxxx>
> >
> > ---
> >
> > Changes in v2:
> > - Fix typo of dev_info msg
> > - remove unused dmach from declaration of dw_mci_dma_slave
> >
> >   drivers/mmc/host/Kconfig        |  24 +++++-
> >   drivers/mmc/host/dw_mmc-pltfm.c |   4 +
> >   drivers/mmc/host/dw_mmc.c       | 169
> > ++++++++++++++++++++++++++++++++++++++-- include/linux/mmc/dw_mmc.h      |
> > 18 ++++-
> >   4 files changed, 205 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
> > index 6a0f9c7..2a66b08 100644
> > --- a/drivers/mmc/host/Kconfig
> > +++ b/drivers/mmc/host/Kconfig
> > @@ -607,16 +607,36 @@ config MMC_DW
> >   	help
> >   	  This selects support for the Synopsys DesignWare Mobile Storage IP
> >   	  block, this provides host support for SD and MMC interfaces, in both
> > -	  PIO and external DMA modes.
> > +	  PIO, internal DMA mode and external DMA modes.
> > +
> > +choice
> > +	prompt "DesignWare MMC transfer mode"
> > +	depends on MMC_DW
> > +
> > +config MMC_DW_PIO
> > +	bool "Use PIO transfers only"
> > +	help
> > +	  Use PIO to transfer data between memory and the hardware.
> > +	  PIO is slower than DMA as it requires CPU instructions to
> > +	  move the data. This has been the traditional default for
> > +	  the DW MCI driver.
> >
> >   config MMC_DW_IDMAC
> >   	bool "Internal DMAC interface"
> > -	depends on MMC_DW
> >   	help
> >   	  This selects support for the internal DMAC block within the Synopsys
> >   	  Designware Mobile Storage IP block. This disables the external DMA
> >   	  interface.
> >
> > +config MMC_DW_EDMAC
> > +	bool "External DMAC interface"
> > +	help
> > +	  This selects support for the external DMAC block outside the Synopsys
> > +	  Designware Mobile Storage IP block. This disables the internal DMA
> > +	  interface.
> > +
> > +endchoice
> > +
> more a drive-by comment:
>
> This should definitly not be a "choice". We're in multiplatform times, where
> you can have support for a multitude of socs using dw_mmc in one kernel. And
> one might want to use pio, one might want to use the internal dma while
> another one might want to use the external dma.
>
> So which dma to use should definitly be decided at runtime and not at compile-
> time.

Thanks for comment, Heiko.
Definitly it should be decided at runtime. So more DT-bindings' patches 
should be
ACKed as well if we want to remove all the compile-time transfer mode.

Hi, Jaehoon Chung
Any suggestion?

> Heiko


--
Shawn Lin


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