[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: Tuesday, January 23, 2018 7:23 AM
> To: Siva Durga Prasad Paladugu <sivadur at xilinx.com>; u-
> boot at lists.denx.de
> Cc: Vipul Kumar <vipulk at xilinx.com>
> Subject: Re: [RFC PATCH] mmc: Skipping the MMC initialization at the boot
> time
> 
> Hi Siva,
> 
> On 01/22/2018 08:03 PM, Siva Durga Prasad Paladugu wrote:
> > 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
> 
> Then did you check how much time can save?
I didn’t measured, but it will definitely decrease eventhough it can be minimal.
> If user want to save the booting time, will not enter to uboot console?
Yes, user doesn’t need to enter u-boot console, he can simply execute boot command as per environment
and that env may contain corresponding/required mmc init only.

> Well..I didn't agree about saving the booting time.
> 
> If you need to add this config, could you explain in more detail.
> And how many board do enable this config in ./configs/ ?

I see it as an option, anyone can enable if they see value for them or
need boot time improvement.
For me, it's just one config in configs/ as of now.

Thanks,
Siva

> 
> Best Regards,
> Jaehoon Chung
> 
> >
> > 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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