eMMC host invokes Mmc_rescan discovery device

When the mmc_start_host is invoked to enable a EMMC host
void Mmc_start_host (struct mmc_host *host)
{
Host->f_init = Max (freqs[0], host->f_min);
host->rescan_disable = 0;
Host->ios.power_mode = mmc_power_undefined;

Mmc_claim_host (host);
if (HOST->CAPS2 & Mmc_cap2_no_prescan_powerup)
Mmc_power_off (host);
Else
MMC_POWER_UP (host, host->ocr_avail);
Mmc_release_host (host);

MMC_GPIOD_REQUEST_CD_IRQ (host);
_mmc_detect_change (host, 0, false);
}
In Mmc_start_host, _mmc_detect_change is used to start the scan connected to the MMC on this host device
static void _mmc_detect_change (struct mmc_host *host, unsigned long delay,
BOOL CD_IRQ)
{
/*
* If The device is configured as wakeup, we prevent a new sleep for
* 5 s to give provision for user spaces to consume the event.
*/
if (CD_IRQ &&! ( Host->caps & Mmc_cap_needs_poll) &&
Device_can_wakeup (Mmc_dev (host))
Pm_wakeup_event (Mmc_dev (host), 5000);

Host->detect_change = 1;
Mmc_schedule_delayed_work (&host->detect, delay);
}
Place Host->detect_change, and call Mmc_schedule_delayed_work to scan device
static int mmc_schedule_delayed_work (struct delayed_work *work,
unsigned long delay)
{
Return Queue_delayed_work (SYSTEM_FREEZABLE_WQ, work, delay);
}
But this host->detect this work corresponding Func is assigned in the following way
The assignment in Mmc_alloc_host is as follows:
Init_delayed_work (&host->detect, Mmc_rescan);
So when you call Mmc_schedule_delayed_work, you call the Mmc_rescan
The most wanted in Mmc_rescan is as follows:
for (i = 0; i < array_size (freqs); i++) {
if (!mmc_rescan_try_freq (host, Max (freqs[i), host->f_min))
Break
if (Freqs[i] <= host->f_min)
Break
}

static const unsigned freqs[] = {400000, 300000, 200000, 100000};
Can see each host up to scan four times, find device on the current FREQS exit
static int mmc_rescan_try_freq (struct mmc_host *host, unsigned freq)
{
Host->f_init = freq;

#ifdef Config_mmc_debug
Pr_info ("%s:%s:trying to init card at%u hz\n",
Mmc_hostname (host), __func__, host->f_init);
#endif
MMC_POWER_UP (host, host->ocr_avail);

/*
* Some Emmcs (with VCCQ-always on)
* Do a hardware reset if possible.
*/
Mmc_hw_reset_for_init (host);

/*
* Sdio_reset sends CMD52 to reset card. Since We do not know
* If the is being re-initialized, just send it. CMD52
* should be ignored by SD/EMMC cards.
* Skip it if we already know that we did not support SDIO commands
*/
if (!) ( HOST-&GT;CAPS2 & Mmc_cap2_no_sdio))
Sdio_reset (host);

Mmc_go_idle (host);

if (!) ( HOST-&GT;CAPS2 & MMC_CAP2_NO_SD))
Mmc_send_if_cond (host, host->ocr_avail);

/* order ' s important:probe SDIO, then SD, then MMC * *
if (!) ( HOST-&GT;CAPS2 & Mmc_cap2_no_sdio))
if (!mmc_attach_sdio (host))
return 0;

if (!) ( HOST-&GT;CAPS2 & MMC_CAP2_NO_SD))
if (!MMC_ATTACH_SD (host))
return 0;

if (!) ( HOST-&GT;CAPS2 & Mmc_cap2_no_mmc))
if (!MMC_ATTACH_MMC (host))
return 0;

Mmc_power_off (host);
Return-eio;
}

Can see from the Mmc_rescan_try_freq, eMMC host can hang three kinds of equipment, these three kinds of sets can only hang one can not coexist, and have a certain priority
Where priority is: Mmc->sd->sdio
Take Mmc_attach_sdio->mmc_add_card as an example to print the following log
[11.565233] mmc_host Mmc2:bus speed (slot 0) = 25000000Hz (slot req 2500000)
+ + Setting up Mdev
[11.587289] mmc2:queuing unknown CIS tuple 0x91 (3 bytes)
[11.599206] mmc2:new SDIO card at address 0001

In Mmc_rescan_try_freq, HOST-&GT;CAPS2 & Mmc_cap2_no_sdio are used to determine whether there is a SDIO, that is, if you do not add this mmc_of_parse in flag the default call MMC_ Attach_sdio. The Mmc_of_parse is the DTS corresponding to the parse host, which means that in DTS, if there is no
if (Of_property_read_bool (NP, "No-sdio"))
HOST-&GT;CAPS2 |= Mmc_cap2_no_sdio;
Call Mmc_attach_sdio on the default

int mmc_of_parse (struct mmc_host *host)
{

if (Of_property_read_bool (NP, "DISABLE-WP"))
HOST-&GT;CAPS2 |= Mmc_cap2_no_write_protect;

* * The comment on CD inversion above * *
if (ro_cap_invert ^ ro_gpio_invert)
HOST-&GT;CAPS2 |= Mmc_cap2_ro_active_high;

if (Of_property_read_bool (NP, "Cap-sd-highspeed"))
Host->caps |= Mmc_cap_sd_highspeed;
if (Of_property_read_bool (NP, "Cap-mmc-highspeed"))
Host->caps |= Mmc_cap_mmc_highspeed;
if (Of_property_read_bool (NP, "Sd-uhs-sdr12"))
Host->caps |= Mmc_cap_uhs_sdr12;
if (Of_property_read_bool (NP, "Sd-uhs-sdr25"))
Host->caps |= Mmc_cap_uhs_sdr25;
if (Of_property_read_bool (NP, "Sd-uhs-sdr50"))
Host->caps |= Mmc_cap_uhs_sdr50;
if (Of_property_read_bool (NP, "sd-uhs-sdr104"))
Host->caps |= mmc_cap_uhs_sdr104;
if (Of_property_read_bool (NP, "Sd-uhs-ddr50"))
Host->caps |= Mmc_cap_uhs_ddr50;
if (Of_property_read_bool (NP, "Cap-power-off-card"))
Host->caps |= Mmc_cap_power_off_card;
if (Of_property_read_bool (NP, "Cap-mmc-hw-reset"))
Host->caps |= Mmc_cap_hw_reset;
if (Of_property_read_bool (NP, "CAP-SDIO-IRQ"))
Host->caps |= Mmc_cap_sdio_irq;
if (Of_property_read_bool (NP, "Full-pwr-cycle"))
HOST-&GT;CAPS2 |= mmc_cap2_full_pwr_cycle;
if (Of_property_read_bool (NP, "Keep-power-in-suspend"))
Host->pm_caps |= Mmc_pm_keep_power;

}