[U-Boot] [RFC PATCH] mmc: Skipping the MMC initialization at the boot time

[Siva Durga Prasad Paladugu]

Hi Jaehoon,

> -----Original Message-----
> From: Jaehoon Chung [mailto:jh80.chung at samsung.com]
> Sent: Thursday, January 18, 2018 1:46 PM
> To: Siva Durga Prasad Paladugu <sivadur at xilinx.com>; u-
> boot at lists.denx.de
> Cc: Vipul Kumar <vipulk at xilinx.com>; Vipul Kumar <vipulk at xilinx.com>;
> Siva Durga Prasad Paladugu <sivadur at xilinx.com>
> Subject: Re: [RFC PATCH] mmc: Skipping the MMC initialization at the boot
> time
> 
> On 01/18/2018 02:40 PM, Siva Durga Prasad Paladugu wrote:
> > From: Vipul Kumar <vipul.kumar at xilinx.com>
> >
> > By enabling CONFIG_SKIP_EARLY_MMC_INIT config, user can skip the
> MMC
> > initialization at the boot time. After getting the u-boot console,
> > user can select the device using mmc dev and can communicate with that.
> > This is useful where user don't want to perform mmc initialization
> > while booting and can do explicitly later as per choice.
> 
> Is there any use-case? What benefit can user have with this config?
> According to commit-msg, user will choose the mmc device later.
> Is it same with initializing at booting time?
Yes, there may be case, where we have both controllers enabled but user would like to
Communicate with only one at u-boot and this selection also depends on environment
Or something which will be updated from external world then in this case, user will initialize
Later as per his wish. This may save bootime as it initializes only the required one and choice of 
which one to initialize

Thanks,
Siva

> 
> >
> > Signed-off-by: Vipul Kumar <vipulk at xilinx.com>
> > Signed-off-by: Siva Durga Prasad Paladugu <sivadur at xilinx.com>
> > ---
> >  common/board_r.c    | 4 ++--
> >  drivers/mmc/Kconfig | 7 +++++++
> >  2 files changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/common/board_r.c b/common/board_r.c index
> > 2a9df6b..8727b93 100644
> > --- a/common/board_r.c
> > +++ b/common/board_r.c
> > @@ -421,7 +421,7 @@ static int initr_onenand(void)  }  #endif
> >
> > -#ifdef CONFIG_MMC
> > +#if defined(CONFIG_MMC) &&
> !defined(CONFIG_SKIP_EARLY_MMC_INIT)
> >  static int initr_mmc(void)
> >  {
> >         puts("MMC:   ");
> > @@ -768,7 +768,7 @@ static init_fnc_t init_sequence_r[] = {  #ifdef
> > CONFIG_CMD_ONENAND
> >         initr_onenand,
> >  #endif
> > -#ifdef CONFIG_MMC
> > +#if defined(CONFIG_MMC) &&
> !defined(CONFIG_SKIP_EARLY_MMC_INIT)
> >         initr_mmc,
> >  #endif
> >         initr_env,
> > diff --git a/drivers/mmc/Kconfig b/drivers/mmc/Kconfig index
> > ab0627a..05b1503 100644
> > --- a/drivers/mmc/Kconfig
> > +++ b/drivers/mmc/Kconfig
> > @@ -40,6 +40,13 @@ config SPL_DM_MMC
> >
> >  if MMC
> >
> > +config SKIP_EARLY_MMC_INIT
> > +       bool "Skip the MMC initialization at boot time"
> > +       help
> > +         Skip the MMC initialization at the boot time. After getting the u-
> boot
> > +         console, user need to set mmc device and after setting the mmc
> dev, user
> > +         can communicate with that device.
> > +
> >  config ARM_PL180_MMCI
> >         bool "ARM AMBA Multimedia Card Interface and compatible
> support"
> >         depends on DM_MMC && OF_CONTROL
> > --
> > 2.7.4
> >
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