Re: [BUG] CMD52 sent as first command not CMD0

Albert Herranz
2011-02-06T11:19:46Z

Hi,

On 02/06/2011 02:35 AM, Philip Rakity wrote:
>
> proposed solution: I cannot verify this fix until Monday.
> =====
>
> CMD52 is a reset for SDIO cards. CMD0 is not sufficient when
> the card is being re-initialized. Only send CMD52 if
> a) doing a reinitialize
> b) card is SDIO or SDIO_COMBO
>
> Signed-off-by: Philip Rakity <prakity@marvell.com>
> ---
> drivers/mmc/core/core.c | 7 ++++++-
> 1 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 30d4da4..f0ce6f6 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1521,7 +1521,12 @@ static int mmc_rescan_try_freq(struct mmc_host *host, unsigned freq)
> mmc_hostname(host), __func__, host->f_init);
> #endif
> mmc_power_up(host);
> - sdio_reset(host);
> +
> + /* reset sdio before CMD0 when card is being reinitialized */
> + if (host->card &&
> + (host->card->type == MMC_TYPE_SDIO ||
> + host->card->type == MMC_TYPE_SD_COMBO))
> + sdio_reset(host);
> mmc_go_idle(host);
> mmc_hwungate_clock(host);
>

At least on the Nintendo Wii, a platform reset _does not_ reset the SDIO hardware, and there is no known way to power-off/power-on it.
So, in some cases like after a system reboot, we need to issue a CMD52 before a CMD0 (even if on that particular case host->card is NULL) to properly reset the Nintendo Wii SDIO-based Wireless LAN card from its previous state, otherwise the card is not detected.

The proposed fix breaks this and makes the card unavailable after a system reboot.

If you are concerned about unconditionally issuing a CMD52 then we can use a quirk to make sure that we always perform a SDIO reset at least for the Nintendo Wii.

Cheers,
Albert