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

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

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.

Cheers,
Ahmad

> 
> Sascha
> 
> 


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