Re: [PATCH v2] mci: add new MCI_BROKEN_CD option for testing

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hi,

On 08.08.22 15:55, Sascha Hauer wrote:
> On Mon, Aug 08, 2022 at 03:43:17PM +0200, Ahmad Fatoum wrote:
>> Hello Sascha,
>>
>> On 08.08.22 15:40, Sascha Hauer wrote:
>>> On Mon, Jul 25, 2022 at 01:58:56PM +0200, Ahmad Fatoum wrote:
>>>> In remote labs co-located with other hardware, we've observed card
>>>> detect levers of different boards to sporadically fail to detect
>>>> the card, e.g. because the cable on the usbsdmux was yanked around
>>>> by accident. When this happens, barebox usually boots up normally as
>>>> the card detect is ignored and then Linux waits indefinitely for
>>>> the card-detect to turn active. Add a new config option that can be
>>>> enabled to avoid these issues altogether.
>>>>
>>>> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
>>>> ---
>>>> v1 -> v2:
>>>>   - use early exit instead of if-else
>>>>   - don't fail mci_card_probe if of_register_fixup fails
>>>> ---
>>>>  drivers/mci/Kconfig    | 15 +++++++++++++++
>>>>  drivers/mci/mci-core.c | 36 ++++++++++++++++++++++++++++++++----
>>>>  2 files changed, 47 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/mci/Kconfig b/drivers/mci/Kconfig
>>>> index 21d53c0c3f0b..651e59259790 100644
>>>> --- a/drivers/mci/Kconfig
>>>> +++ b/drivers/mci/Kconfig
>>>> @@ -56,6 +56,21 @@ config MCI_MMC_GPP_PARTITIONS
>>>>  	  Note: by default, 'MMC' devices have no 'general purpose partitions',
>>>>  	  it requires a special one-time configuration step to enable them.
>>>>  
>>>> +config MCI_BROKEN_CD
>>>> +	bool "ignore card-detect pin on boot and in OS"
>>>> +	help
>>>> +	  Say 'y' here to have barebox unconditionally ignore the
>>>> +	  card-detect pin for its own operation and manipulate the
>>>> +	  kernel DT, so all detected MCI cards are polled instead
>>>> +	  of expecting the card detect lever to behave correctly.
>>>> +	  If you need more fine grained control use of_property
>>>> +	  in an init script:
>>>> +
>>>> +	    of_property -fd mmc0 cd-gpios
>>>> +	    of_property -fs mmc0 broken-cd
>>>> +
>>>> +	  If unsure, say 'n' here.
>>>> +
>>>>  comment "--- MCI host drivers ---"
>>>>  
>>>>  config MCI_DW
>>>> diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
>>>> index 82e2f82f5377..4db2253c3a80 100644
>>>> --- a/drivers/mci/mci-core.c
>>>> +++ b/drivers/mci/mci-core.c
>>>> @@ -1727,6 +1727,27 @@ static int mci_register_partition(struct mci_part *part)
>>>>  	return 0;
>>>>  }
>>>>  
>>>> +static int of_broken_cd_fixup(struct device_node *root, void *ctx)
>>>> +{
>>>> +	struct device_d *hw_dev = ctx;
>>>> +	struct device_node *np;
>>>> +	char *name;
>>>> +
>>>> +	name = of_get_reproducible_name(hw_dev->device_node);
>>>> +	np = of_find_node_by_reproducible_name(root, name);
>>>> +	free(name);
>>>> +	if (!np) {
>>>> +		dev_warn(hw_dev, "Cannot find nodepath %s, cannot fixup\n",
>>>> +			 hw_dev->device_node->full_name);
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	of_property_write_bool(np, "cd-gpios", false);
>>>> +	of_property_write_bool(np, "broken-cd", true);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>>  /**
>>>>   * Probe an MCI card at the given host interface
>>>>   * @param mci MCI device instance
>>>> @@ -1737,10 +1758,13 @@ static int mci_card_probe(struct mci *mci)
>>>>  	struct mci_host *host = mci->host;
>>>>  	int i, rc, disknum, ret;
>>>>  
>>>> -	if (host->card_present && !host->card_present(host) &&
>>>> -	    !host->non_removable) {
>>>> -		dev_err(&mci->dev, "no card inserted\n");
>>>> -		return -ENODEV;
>>>> +	if (host->card_present && !host->card_present(host) && !host->non_removable) {
>>>> +		if (!IS_ENABLED(CONFIG_MCI_BROKEN_CD)) {
>>>> +			dev_err(&mci->dev, "no card inserted\n");
>>>> +			return -ENODEV;
>>>> +		}
>>>> +
>>>> +		dev_info(&mci->dev, "no card inserted (ignoring)\n");
>>>>  	}
>>>>  
>>>>  	ret = regulator_enable(host->supply);
>>>> @@ -1818,6 +1842,10 @@ static int mci_card_probe(struct mci *mci)
>>>>  		}
>>>>  	}
>>>>  
>>>> +	if (IS_ENABLED(CONFIG_MCI_BROKEN_CD) && !host->no_sd &&
>>>> +	    dev_of_node(host->hw_dev))
>>>> +		of_register_fixup(of_broken_cd_fixup, host->hw_dev);
>>>
>>> This fixup is only registered when the card is probed, i.e. when it's
>>> used in barebox. Shouldn't it be registered in mci_register() instead?
>>
>> This is intentional. We only know that cards barebox successfully probed
>> are indeed available.
> 
> I don't get this argument. If card detect is broken then why can't we
> let Linux go through the same steps as barebox when barebox hasn't done
> so?
> 
> Letting the card work in Linux only when it was previously used in barebox
> is surprising to me.

I'll change it into a device parameter applicable to all cards in v3.

Cheers,
Ahmad

> 
> Sascha
> 


-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |