[U-Boot] [PATCH 1/3] samsung: board: support eMMC reset using DT

[Joonyoung Shim <jy0922.shim@samsung.com>]

On 01/12/2015 10:45 AM, Jaehoon Chung wrote:
> On 01/11/2015 02:46 AM, Simon Glass wrote:
>> Hi,
>>
>>
>> On 9 January 2015 at 23:53, Joonyoung Shim <jy0922.shim@samsung.com> wrote:
>>> On 01/09/2015 08:13 PM, Jaehoon Chung wrote:
>>>> On 01/09/2015 04:31 PM, Joonyoung Shim wrote:
>>>>> +Cc Jaehoon,
>>>>>
>>>>> On 01/09/2015 03:18 AM, Simon Glass wrote:
>>>>>> Hi Joonyoung,
>>>>>>
>>>>>> On 7 January 2015 at 22:44, Joonyoung Shim <jy0922.shim@samsung.com> wrote:
>>>>>>> Some exynos boards require special handling of SD4_nRESET_OUT line for
>>>>>>> eMMC memory to perform complete reboot e.g. Odroid X2/U3/XU3 boards.
>>>>>>>
>>>>>>> This will support eMMC reset using DT from reset_misc of samsung common
>>>>>>> board file and each board files can support eMMC reset on non DT case.
>>>>>>>
>>>>>>> Signed-off-by: Joonyoung Shim <jy0922.shim@samsung.com>
>>>>>>> ---
>>>>>>>  board/samsung/common/board.c                   | 27 ++++++++++++++++++++++++++
>>>>>>>  board/samsung/odroid/odroid.c                  |  2 +-
>>>>>>>  doc/device-tree-bindings/exynos/emmc-reset.txt | 15 ++++++++++++++
>>>>>>>  3 files changed, 43 insertions(+), 1 deletion(-)
>>>>>>>  create mode 100644 doc/device-tree-bindings/exynos/emmc-reset.txt
>>>>>>>
>>>>>>> diff --git a/board/samsung/common/board.c b/board/samsung/common/board.c
>>>>>>> index c04ab3c..3218463 100644
>>>>>>> --- a/board/samsung/common/board.c
>>>>>>> +++ b/board/samsung/common/board.c
>>>>>>> @@ -40,6 +40,8 @@ __weak int exynos_power_init(void)
>>>>>>>         return 0;
>>>>>>>  }
>>>>>>>
>>>>>>> +__weak void exynos_reset_misc(void) {}
>>>>>>> +
>>>>>>>  #if defined CONFIG_EXYNOS_TMU
>>>>>>>  /* Boot Time Thermal Analysis for SoC temperature threshold breach */
>>>>>>>  static void boot_temp_check(void)
>>>>>>> @@ -400,3 +402,28 @@ int misc_init_r(void)
>>>>>>>         return 0;
>>>>>>>  }
>>>>>>>  #endif
>>>>>>> +
>>>>>>> +void reset_misc(void)
>>>>>>> +{
>>>>>>> +#ifdef CONFIG_OF_CONTROL
>>>>>>
>>>>>> I think all Samsung boards have this defined, so this #ifdef can be removed.
>>>>>>
>>>>>
>>>>> OK, if it is true, we can remove this and i will not to support non DT case.
>>>>>
>>>>>>> +       struct gpio_desc gpio = {};
>>>>>>> +       int node;
>>>>>>> +
>>>>>>> +       node = fdt_node_offset_by_compatible(gd->fdt_blob, 0,
>>>>>>> +                       "samsung,emmc-reset");
>>>>>>> +       if (node < 0)
>>>>>>> +               return;
>>>>>>> +
>>>>>>> +       gpio_request_by_name_nodev(gd->fdt_blob, node, "reset-gpio", 0, &gpio,
>>>>>>> +                                  GPIOD_IS_OUT);
>>>>>>> +
>>>>>>> +       if (dm_gpio_is_valid(&gpio)) {
>>>>>>> +               /* Reset eMMC*/
>>>>>>> +               dm_gpio_set_value(&gpio, 0);
>>>>>>> +               mdelay(10);
>>>>>>
>>>>>> That's a very long reset! Is that what it needs?
>>>>>>
>>>>>
>>>>> Jaehoon, is there any guide about wait time of reset at eMMC spec?
>>>>
>>>> Well, I'm not sure, but as Simon's comments, it's long time.
>>>> (Minimum is 1us...Maximum isn't defined.)
>>>>
>>>
>>> This just comes from reset_misc() of board/samsung/odroid/odroid.c file.
>>> Even, hardkernel u-boot waits 50msec.
>>
>> The only info I have immediately to hand is the 'JEDEC Standard No.
>> 84-A441' (eMMC) and it says a 1uS pulse is required. So can we change
>> this to udelay(1)?
> 
> It's minimum value, that's not problem that 10msec is set.
> But if change this value, i think good that it changes to greater value than 1us.
> 

Actually, i don't have any idea about proper wait time, so i will use
just current 10msec with TODO comments until getting right guide about
wait time. Is it ok?

Thanks.