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

Thu Jan 4 12:05:54 UTC 2018

On Thu, Jan 4, 2018 at 2:02 PM, Uri Mashiach
<uri.mashiach at compulab.co.il> wrote:
>
>
> On 01/04/2018 01:37 PM, Stefano Babic wrote:
>>
>> On 04/01/2018 11:56, Eran Matityahu wrote:
>>>
>>> On Thu, Jan 4, 2018 at 12:42 PM, Stefano Babic <sbabic at denx.de> wrote:
>>>>
>>>> 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.
>>>>>
>>> We are saying the same thing.
>>
>>
>> :-)
>>
>>> Except, you are wrong in one little thing: the i.MX6 version of
>>> spl_boot_device() doesn't return an imx6_bmode. It detects the
>>> imx6_bmode and returns a BOOT_DEVICE_*.
>>
>>
>> True, but this is used as "type" for i.MX6, it is a real device for
>> i.MX7 (get_boot_device() in arch/arm/mach-imx/mx7/soc.c). This is also
>> due to differences in SOC, I admit.
>>
>>> In case of an MMC/.SD boot mode it returns BOOT_DEVICE_MMC1.
>>> This patch indeed makes the i.MX7 behaviour the same as i.MX6.
>>
>>
>> The thing is if this patch breaks some boards. As far as I can see,
>> there is just 2 i.MX7 with SPL support: colibri_imx7 (it has just
>> USDHC1, no problem) and cl-som-imx7 that initialize MMC3 (but I do not
>> know if it boots from it, in any case it is not MMC2). Uri, you
>> commented this patch and you are the maintainer for cl-som-imx7. Do you
>> see any problem with that ?
>
>
> The cl-som-imx7 board doesn't boot from MMC3, so the patch doesn't influence
> the board.
>
> I prefer the approach of using the spl_boot_list instead of "loosing" the
> boot instance, that might be used in other future boards.

You do not actually lose the boot instance.
You can always use get_boot_device().

Regards,
Eran
>
> --
> Regards,
> Uri