Re: [PATCH] mci: core: add device parameter for eMMC boot ack

[Sascha Hauer <s.hauer@pengutronix.de>]

On Wed, May 13, 2020 at 01:46:36PM +0200, Lucas Stach wrote:
> This adds an easy way to enable the boot acknowledge function of
> a eMMC device, without the need to frob the EXT_CSD setting via
> the mmc_extcsd command.
> A boot ack is required whenever the boot partitions are read via
> the fast initialization boot protocol.
> 
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> ---
>  drivers/mci/mci-core.c | 33 +++++++++++++++++++++++++++------
>  include/mci.h          |  2 ++
>  2 files changed, 29 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/mci/mci-core.c b/drivers/mci/mci-core.c
> index f3718327f18d..d33bc0c1a41e 100644
> --- a/drivers/mci/mci-core.c
> +++ b/drivers/mci/mci-core.c
> @@ -516,6 +516,7 @@ static int mmc_change_freq(struct mci *mci)
>  
>  		mci->ext_csd_part_config = mci->ext_csd[EXT_CSD_PARTITION_CONFIG];
>  		mci->bootpart = (mci->ext_csd_part_config >> 3) & 0x7;
> +		mci->boot_ack_enable = (mci->ext_csd_part_config >> 6) & 0x1;
>  	}
>  
>  	return 0;
> @@ -1592,6 +1593,17 @@ static int mci_set_boot(struct param_d *param, void *priv)
>  			  EXT_CSD_PARTITION_CONFIG, mci->ext_csd_part_config);
>  }
>  
> +static int mci_set_boot_ack(struct param_d *param, void *priv)
> +{
> +	struct mci *mci = priv;
> +
> +	mci->ext_csd_part_config &= ~(0x1 << 6);
> +	mci->ext_csd_part_config |= mci->boot_ack_enable << 6;
> +
> +	return mci_switch(mci,
> +			  EXT_CSD_PARTITION_CONFIG, mci->ext_csd_part_config);
> +}

There's only one correct setting for each board or SoC. Instead of
letting the user choose between right and wrong, can't we add a hook to
be called from the board/SoC code? A device tree property might be an
option as well, something like barebox,enable-boot-ack.

There are also bits to change the bus width after power up which might
need adjustments which would mean another parameter with the current
approach.

Sascha

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