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

[Jaehoon Chung]

Hi Siva,

On 01/23/2018 06:29 PM, Siva Durga Prasad Paladugu wrote:
> 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.

I understood what you really want. :) Well, can i keep this RFC patch for considering more?
In future, will need to apply this patch..then i will request to you the patch, not RFC. :)

Best Regards,
Jaehoon Chung

> 
> 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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>>>>>
>>>>>
>>>
>