Re: [PATCH 2/2] mmc: dw_mmc: add resets support to dw_mmc

Jaehoon Chung
2016-03-29T06:15:29Z

On 03/29/2016 03:09 PM, Shawn Lin wrote:
> 在 2016/3/29 13:56, Jaehoon Chung 写道:
>> On 03/29/2016 11:22 AM, Shawn Lin wrote:
>>> 在 2016/3/25 13:35, Guodong Xu 写道:
>>>> Hi, Shawn
>>>>
>>>> Sorry I replied late. I added comments below.
>>>>
>>>> On 6 March 2016 at 22:16, Shawn Lin <shawn.lin@rock-chips.com
>>>> <mailto:shawn.lin@rock-chips.com>> wrote:
>>>>
>>>> On 2016/3/6 16:47, Guodong Xu wrote:
>>>>
>>>> mmc registers may in abnormal state if mmc is used in bootloader,
>>>> eg. to support booting from eMMC. So we need reset mmc registers
>>>> when kernel boots up, instead of assuming mmc is in clean state.
>>>>
>>>> With this patch, user can add a 'resets' property into dw_mmc dts
>>>> node. When driver parse_dt and probe, it calls reset API to
>>>> deassert the 'reset' of dw_mmc host controller. When probe error or
>>>> remove, it calls reset API to assert it.
>>>>
>>>> Please also refer to
>>>> Documentation/devicetree/bindings/reset/reset.txt
>>>>
>>>> Signed-off-by: Guodong Xu <guodong.xu@linaro.org
>>>> <mailto:guodong.xu@linaro.org>>
>>>> Signed-off-by: Xinwei Kong <kong.kongxinwei@hisilicon.com
>>>> <mailto:kong.kongxinwei@hisilicon.com>>
>>>> Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org
>>>> <mailto:zhangfei.gao@linaro.org>>
>>>>
>>>>
>>>> Really should V2 and add the changelog.
>>>>
>>>>
>>>> Yes, will do. next version I sent will be labelled as V3.
>>>>
>>>>
>>>>
>>>> ---
>>>> drivers/mmc/host/dw_mmc.c | 22 +++++++++++++++++++++-
>>>> 1 file changed, 21 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>>>> index 242f9a0..281ea9c 100644
>>>> --- a/drivers/mmc/host/dw_mmc.c
>>>> +++ b/drivers/mmc/host/dw_mmc.c
>>>> @@ -2878,6 +2878,14 @@ static struct dw_mci_board
>>>> *dw_mci_parse_dt(struct dw_mci *host)
>>>> if (!pdata)
>>>> return ERR_PTR(-ENOMEM);
>>>>
>>>> + /* find reset controller when exist */
>>>> + pdata->rstc = devm_reset_control_get_optional(dev, NULL);
>>>> + if (IS_ERR(pdata->rstc)) {
>>>> + if (PTR_ERR(pdata->rstc) == -EPROBE_DEFER)
>>>> + return ERR_PTR(-EPROBE_DEFER);
>>>> + pdata->rstc = NULL;
>>>>
>>>>
>>>> maybe we can remove "pdata->rstc = NULL", and directly
>>>> use IS_ERR(..) for the following "if (host->pdata->rstc != NULL)"
>>>> statement
>>>>
>>>>
>>>> Yes, will do.
>>>> I see your point, other lines in this file are using IS_ERR(!..), I will
>>>> use this style too.
>>>>
>>>> + }
>>>> +
>>>> /* find out number of slots supported */
>>>> of_property_read_u32(np, "num-slots", &pdata->num_slots);
>>>>
>>>> @@ -2949,7 +2957,9 @@ int dw_mci_probe(struct dw_mci *host)
>>>>
>>>> if (!host->pdata) {
>>>> host->pdata = dw_mci_parse_dt(host);
>>>> - if (IS_ERR(host->pdata)) {
>>>> + if (PTR_ERR(host->pdata) == -EPROBE_DEFER)
>>>> + return -EPROBE_DEFER;
>>>>
>>>>
>>>> please fix the coding style here.
>>>>
>>>>
>>>> Do you mean to add additional {} for this 'if' , like this?
>>>>
>>>> + if (PTR_ERR(host->pdata) == -EPROBE_DEFER) {
>>>> + return -EPROBE_DEFER;
>>>>
>>>> + }
>>>>
>>>> I will add {}.
>>>>
>>>>
>>>>
>>>> + else if (IS_ERR(host->pdata)) {
>>>> dev_err(host->dev, "platform data not
>>>> available\n");
>>>> return -EINVAL;
>>>> }
>>>> @@ -3012,6 +3022,9 @@ int dw_mci_probe(struct dw_mci *host)
>>>> }
>>>> }
>>>>
>>>> + if (host->pdata->rstc != NULL)
>>>> + reset_control_deassert(host->pdata->rstc);
>>>> +
>>>>
>>>>
>>>> sorry, I can't follow your intention here. Shouldn't it be something
>>>> like "assert mmc -> may need delay -> deassert mmc". As your current
>>>> code, nothing happend right?
>>>>
>>>>
>>>> The chip exits from bootloader with this bit asserted. And when entering
>>>> kernel, we only need to deassert.
>>>>
>>>> In my current code, the driver deassert mmc in _probe(), and assert mmc
>>>> in _remove().
>>>
>>> I catch your point. From the previous discussion, we add it to make sure
>>> dw_mmc in good state after leaving bootloader to kernel. But My real question is that you can assert it in bootloader, so you can also
>>> dessert it in bootloaer to make sure dw_mmc work fine when probing
>>> in kernel. In that way, we don't need this patch?
>>
>> Doesn't dw_mci_hw_reset work fine? I think that card should be reset with MMC_CAP_HW_RESET.
>> Could you check this?
>>
>
> MMC_CAP_HW_RESET actually reset the mmc card, but Guodong means to
> reset the controller rather than mmc card :)

We have talked about FBE scenarios, right? :)
Now, I remembered it.

>
>
>> Best Regards,
>> Jaehoon Chung
>>
>>>
>>> More to think, Is it ok to match the behaviour of bootloader stage?
>>> My bootloader doesn't assert the reset pin of dw_mmc, so it seams if
>>> I want to fix you issue on kernel stage, I need a new round of
>>> assert->delay->deassert.
>>>
>>>
>>>>
>>>>
>>>>
>>>> setup_timer(&host->cmd11_timer,
>>>> dw_mci_cmd11_timer, (unsigned long)host);
>>>>
>>>> @@ -3164,6 +3177,9 @@ err_dmaunmap:
>>>> if (host->use_dma && host->dma_ops->exit)
>>>> host->dma_ops->exit(host);
>>>>
>>>> + if (host->pdata->rstc != NULL)
>>>> + reset_control_assert(host->pdata->rstc);
>>>> +
>>>> err_clk_ciu:
>>>> if (!IS_ERR(host->ciu_clk))
>>>> clk_disable_unprepare(host->ciu_clk);
>>>> @@ -3196,11 +3212,15 @@ void dw_mci_remove(struct dw_mci *host)
>>>> if (host->use_dma && host->dma_ops->exit)
>>>> host->dma_ops->exit(host);
>>>>
>>>> + if (host->pdata->rstc != NULL)
>>>> + reset_control_assert(host->pdata->rstc);
>>>> +
>>>> if (!IS_ERR(host->ciu_clk))
>>>> clk_disable_unprepare(host->ciu_clk);
>>>>
>>>> if (!IS_ERR(host->biu_clk))
>>>> clk_disable_unprepare(host->biu_clk);
>>>> +
>>>> }
>>>>
>>>>
>>>> unnecessary new line here.
>>>>
>>>>
>>>> Will fix.
>>>>
>>>> -Guodong
>>>>
>>>>
>>>> EXPORT_SYMBOL(dw_mci_remove);
>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Best Regards
>>>> Shawn Lin
>>>>
>>>>
>>>
>>>
>>>
>>
>>
>>
>>
>
>