[U-Boot] [PATCH 1/2] imx7: spl: Use SPL boot device MMC1 for all of the SOCs MMC/SD boot devices

[Stefano Babic]

On 04/01/2018 11:11, Eran Matityahu wrote:
> On Thu, Jan 4, 2018 at 12:02 PM, Eran Matityahu <eran.m at variscite.com> wrote:
>> On Thu, Jan 4, 2018 at 11:14 AM, Stefano Babic <sbabic at denx.de> wrote:
>>> Hi Eran,
>>>
>>> On 03/01/2018 14:58, Eran Matityahu wrote:
>>>> Hi Uri.
>>>>
>>>>> Hello Eran,
>>>>>
>>>>> On 01/03/2018 12:53 PM, Eran Matityahu wrote:
>>>>>>
>>>>>> Use only one SPL MMC device, similarly to the iMX6 code
>>>>>
>>>>>
>>>>> What is the reason for not using MMC2?
>>>>
>>>> The reason is so that you won't have to initialize more than one MMC
>>>> device in SPL.
>>>> Also, to be consistent with the iMX6 SPL code.
>>>>
>>>>>
>>>>>>
>>>>>> Signed-off-by: Eran Matityahu <eran.m at variscite.com>
>>>>>> ---
>>>>>>   arch/arm/mach-imx/spl.c | 3 +--
>>>>>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/arch/arm/mach-imx/spl.c b/arch/arm/mach-imx/spl.c
>>>>>> index d0d1b73aa6..6b5bd8990c 100644
>>>>>> --- a/arch/arm/mach-imx/spl.c
>>>>>> +++ b/arch/arm/mach-imx/spl.c
>>>>>> @@ -106,10 +106,9 @@ u32 spl_boot_device(void)
>>>>>>         switch (boot_device_spl) {
>>>>>>         case SD1_BOOT:
>>>>>>         case MMC1_BOOT:
>>>>>> -               return BOOT_DEVICE_MMC1;
>>>>>>         case SD2_BOOT:
>>>>>>         case MMC2_BOOT:
>>>>>> -               return BOOT_DEVICE_MMC2;
>>>>>> +               return BOOT_DEVICE_MMC1;
>>>>>>         case SPI_NOR_BOOT:
>>>>>>                 return BOOT_DEVICE_SPI;
>>>>>>         default:
>>>
>>> The reason to have spl_boot_device() is not to initialize more as one
>>> MMC device, but to find which storage contains the next image to be
>>> started (u-boot.img). This is generally (but not in all projects) the
>>> same storage from where the BootROM has loaded SPL.
>>>
>>> According to this, this patch seems wrong. If SPL / u-boot.img are
>>> stored on MMC2 (and maybe MMC2 is the only MMC device for the board),
>>> your patch breaks booting.
>>>
>>> If you have special case, you can write a board_boot_order() in your
>>> board code to overwrite the behavior.
>>>
>>> Best regards,
>>> Stefano Babic
>>
>> The iMX6 spl_boot_device() doesn't even check which MMC device the
>> BootROM has loaded SPL from. It just returns BOOT_DEVICE_MMC1
>> in case the boot device was any MMC/SD device, and leaves it to the
>> board code to detect the exact device and init the appropriate device
>> with the next image (u-boot,img), accordingly.
>> My suggestion is to do the same here.
>>
>> In my iMX7 board, I can boot from MMC1 (SD card) and MMC3 (eMMC),
>> but let's say it's MMC2 in sake of this explanation.
>> Without this patch, in order to boot from MMC2 (with both SPL and u-boot.img
>> on MMC2), I have to initialize both MMC1 and MMC2 devices because SPL
>> loops on all devices until it finds a match, and it halts if the first
>> device is not
>> initialized.
>>
>> With this patch I can use get_boot_device() inside board_mmc_init() and
>> only initialize the MMC device I want to load the next image from (usually
>> the same device).
>>
>> I know I can approach it differently and change the spl_boot_list[0] device to
>> BOOT_DEVICE_MMC1 in board_boot_order(), but I figured the behaviour
>> should be the same for iMX6 and iMX7.
>> If you think the correct way is to return BOOT_DEVICE_MMC2, then we
>> should probably also add a BOOT_DEVICE_MMC3 definition, and also change
>> the iMX6 code to do the same.
>>
> By the way, in my opinion, the iMX6 way 

The imx6 way is the right way to do - rather, i.MX7 does not follow the
same approach.

In i.MX6 code, spl_boot_device() returns the type of boot device instead
of the instance of the peripheral. In fact. it returns a imx6_bmode
(let's away the serial rom, it is messy to detect).

A following board_boot_order() then choose which is the instance for
that detected type, and this is then used to load u-boot.img. This is,
at the end, board specific. Even if in most cases, u-boot.img resides on
the same storage as SPL, there are cases where this is not true.

And just a single MMC is instantiated in SPL - this is decided inside
board code. See for example pcm058.c (but there are plenty of other
examples), just a single MMC is initialized by SPL.

On i.MX7, the same approach was not followed. A single spl_boot_device()
tries to do all.

I agree that i.MX6 approach is better, and I will glad if you would move
i.MX7 to have the same behavior as i.MX6.


>(and this patch also),

No, even if it does not depend from the patch - see above.

> is the
> preferred way,
> since usually you'll only need one MMC device in SPL.
> 

Best regards,
Stefano Babic


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