Re: [PATCH] mci: core: add write_reliable device parameter

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

Hello Michael,

On 09.10.24 01:12, Michael Grzeschik wrote:
> Add mmcX.write_reliable parameter so it can be queried by
> scripts and board code.
> 
> Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
> ---
>  drivers/mci/mci-core.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
> index 48a3df9ec9..1b7526abfa 100644
> --- a/drivers/mci/mci-core.c
> +++ b/drivers/mci/mci-core.c
> @@ -2680,6 +2680,22 @@ static int mci_get_partition_setting_completed(struct mci *mci)
>  	return ret;
>  }
>  
> +static int mci_get_write_reliable(struct mci *mci)
> +{
> +	u8 *ext_csd;
> +	int ret;
> +
> +	ext_csd = mci_get_ext_csd(mci);
> +	if (IS_ERR(ext_csd))
> +		return PTR_ERR(ext_csd);
> +
> +	ret = ext_csd[EXT_CSD_WR_REL_SET] & 0x1f;
> +
> +	dma_free(ext_csd);

I know that this is copied off mci_get_partition_setting_completed(),
but why does it need to call mci_get_ext_csd()? Can't we just access
prepopulated mci->ext_csd?

> +
> +	return ret;
> +}> +
>  /**
>   * Probe an MCI card at the given host interface
>   * @param mci MCI device instance
> @@ -2796,6 +2812,13 @@ static int mci_card_probe(struct mci *mci)
>  				"Failed to determine EXT_CSD_PARTITION_SETTING_COMPLETED\n");
>  		else
>  			dev_add_param_bool_fixed(&mci->dev, "partitioning_completed", ret);
> +
> +		ret = mci_get_write_reliable(mci);
> +		if (ret < 0)
> +			dev_dbg(&mci->dev,
> +				"Failed to determine EXT_CSD_WR_REL_SET\n");
> +		else
> +			dev_add_param_bool_fixed(&mci->dev, "write_reliable", ret);

Wouldn't it be confusing for the write reliability setting to remain constant?

For example a script may want to check that the value is not set before running,
but if it's set at runtime, we want the script to notice that on the second run
without having to reset.

I know this would apply to partitioning_completed too.

What do you think?

Cheers,
Ahmad

>  	}
>  
>  	mci_parse_cid(mci);


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