linux-kernel - Re: [PATCH v2 06/14] mmc: dw_mmc: simplify optional reset handling

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Date:   Mon, 20 Mar 2017 11:03:58 +0100
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     linux-mmc@...r.kernel.org, Jaehoon Chung <jh80.chung@...sung.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-kernel@...r.kernel.org,
        "Szyprowski, Marek" <m.szyprowski@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH v2 06/14] mmc: dw_mmc: simplify optional reset handling

Hi Philipp,

On 20.03.2017 10:53, Philipp Zabel wrote:
> On Mon, 2017-03-20 at 10:22 +0100, Andrzej Hajda wrote:
>> Hi Philipp,
>>
>> Todays next branch does not work with exynos5433-tm2 board.
>> I guess this patch causes regression. On MMC without reset controller I
>> get errors:
>> [    4.938222] dwmmc_exynos 15540000.mshc: platform data not available
>> [    4.943268] dwmmc_exynos: probe of 15540000.mshc failed with error -22
>> [    4.950184] dwmmc_exynos 15560000.mshc: platform data not available
>> [    4.955962] dwmmc_exynos: probe of 15560000.mshc failed with error -22
>>
>> Commenting out reset controller get and error checks 'fixes' the issue.
>>
>> On 15.03.2017 12:31, Philipp Zabel wrote:
>>> As of commit bb475230b8e5 ("reset: make optional functions really
>>> optional"), the reset framework API calls use NULL pointers to describe
>>> optional, non-present reset controls.
>>>
>>> This allows to return errors from devm_reset_control_get_optional and to
>>> call reset_control_(de)assert unconditionally.
>>>
>>> Signed-off-by: Philipp Zabel <p.zabel@...gutronix.de>
>>> ---
>>>  drivers/mmc/host/dw_mmc.c | 14 +++++---------
>>>  1 file changed, 5 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/mmc/host/dw_mmc.c b/drivers/mmc/host/dw_mmc.c
>>> index a9ac0b4573131..3d62b0a1f81cb 100644
>>> --- a/drivers/mmc/host/dw_mmc.c
>>> +++ b/drivers/mmc/host/dw_mmc.c
>>> @@ -2968,10 +2968,8 @@ static struct dw_mci_board *dw_mci_parse_dt(struct dw_mci *host)
>>>  
>>>  	/* find reset controller when exist */
>>>  	pdata->rstc = devm_reset_control_get_optional(dev, "reset");
>>> -	if (IS_ERR(pdata->rstc)) {
>>> -		if (PTR_ERR(pdata->rstc) == -EPROBE_DEFER)
>>> -			return ERR_PTR(-EPROBE_DEFER);
>>> -	}
>>> +	if (IS_ERR(pdata->rstc))
>>> +		return ERR_CAST(pdata->rstc);
>>
>> With three lines above commented out it works.
> So devm_reset_control_get_optional returns -EINVAL. Why?
>
> The mshc@...60000 node is compatible to "samsung,exynos7-dw-mshc-smu",
> so that's dw_mmc-exynos.c calling dw_mci_pltfm_register, which then
> calls dw_mci_probe, passing the original platform device as
> host->dev = &pdev->dev, and I expect __of_reset_control_get being called
> with a valid DT node (dev->of_node).
> Since id is set to "reset", of_property_match_string(node,
> "reset-names", id) should then be called and return -EINVAL because the
> "reset-names" property does not exist. Then __of_reset_control_get
> should return NULL because optional == true.
> Some of this obviously doesn't happen, where am I wrong?


When RESET_CONTROLLER is not enabled dummy stubs return -ENOSUPP error [1].

[1]: http://lxr.free-electrons.com/source/include/linux/reset.h#L77

Regards
Andrzej




>
> regards
> Philipp
>
>
>
>