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

[Jaehoon Chung]

On 01/11/2015 02:46 AM, Simon Glass wrote:
> Hi,
> 
> 
> On 9 January 2015 at 23:53, Joonyoung Shim <jy0922.shim at 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 at 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 at 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.

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