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

[Simon Glass]

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)?

Regards,
Simon