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mmc: core: Prevent violation of specs while initializing cards 

According to eMMC/SD/SDIO specs, the VDD (VCC) voltage level must be
maintained during the initialization sequence. If we want/need to tune
the voltage level, a complete power cycle of the card must be executed.

Most host drivers conforms to the specifications by only allowing to
change VDD voltage level at the MMC_POWER_UP state, but some also cares
about MMC_POWER_ON state, which they should'nt. This patch will not
break those drivers, but they could clean up code to better reflect
what is expected from the protocol layer.

A big re-work of the mmc_select_voltage function is done to only change
VDD voltage level if the host supports MMC_CAP2_FULL_PWR_CYCLE.
Otherwise only validation of the host and card ocr mask will be done.

A very nice side-effect of this patch is that we now don't need to
reset the negotiated ocr mask at the mmc_power_off function, since now
it will actually reflect the present voltage level, which safely can be
used at the next power up and re-initialization. Moreover, we then only
need to execute mmc_select_voltage from the attach sequence.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>
This commit is contained in:
Ulf Hansson 2013-09-16 11:28:42 +02:00 committed by Chris Ball
parent 6904115095
commit ce69d37b7d
4 changed files with 13 additions and 37 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
drivers/mmc/core/core.c
View File

@ -1358,21 +1358,20 @@ u32 mmc_select_voltage(struct mmc_host *host, u32 ocr)
int bit;
ocr &= host->ocr_avail;
if (!ocr) {
dev_warn(mmc_dev(host), "no support for card's volts\n");
return 0;
}
bit = ffs(ocr);
if (bit) {
bit -= 1;
if (host->caps2 & MMC_CAP2_FULL_PWR_CYCLE) {
bit = ffs(ocr) - 1;
ocr &= 3 << bit;
mmc_host_clk_hold(host);
host->ios.vdd = bit;
mmc_set_ios(host);
mmc_host_clk_release(host);
mmc_power_cycle(host, ocr);
} else {
pr_warning("%s: host doesn't support card's voltages\n",
mmc_hostname(host));
ocr = 0;
bit = fls(ocr) - 1;
ocr &= 3 << bit;
if (bit != host->ios.vdd)
dev_warn(mmc_dev(host), "exceeding card's volts\n");
}
return ocr;
@ -1571,14 +1570,6 @@ void mmc_power_off(struct mmc_host *host)
host->ios.clock = 0;
host->ios.vdd = 0;
/*
* Reset ocr mask to be the highest possible voltage supported for
* this card. This value will be used at next power up.
*/
if (host->card)
host->card->ocr = 1 << (fls(host->ocr_avail) - 1);
if (!mmc_host_is_spi(host)) {
host->ios.bus_mode = MMC_BUSMODE_OPENDRAIN;
host->ios.chip_select = MMC_CS_DONTCARE;

1
drivers/mmc/core/mmc.c
View File

@ -1535,7 +1535,6 @@ static int mmc_resume(struct mmc_host *host)
mmc_claim_host(host);
mmc_power_up(host, host->card->ocr);
mmc_select_voltage(host, host->card->ocr);
err = mmc_init_card(host, host->card->ocr, host->card);
mmc_release_host(host);

1
drivers/mmc/core/sd.c
View File

@ -1103,7 +1103,6 @@ static int mmc_sd_resume(struct mmc_host *host)
mmc_claim_host(host);
mmc_power_up(host, host->card->ocr);
mmc_select_voltage(host, host->card->ocr);
err = mmc_sd_init_card(host, host->card->ocr, host->card);
mmc_release_host(host);

17
drivers/mmc/core/sdio.c
View File

@ -987,7 +987,6 @@ static int mmc_sdio_resume(struct mmc_host *host)
/* Restore power if needed */
if (!mmc_card_keep_power(host)) {
mmc_power_up(host, host->card->ocr);
mmc_select_voltage(host, host->card->ocr);
/*
* Tell runtime PM core we just powered up the card,
* since it still believes the card is powered off.
@ -1045,7 +1044,6 @@ static int mmc_sdio_resume(struct mmc_host *host)
static int mmc_sdio_power_restore(struct mmc_host *host)
{
int ret;
u32 ocr, rocr;
BUG_ON(!host);
BUG_ON(!host->card);
@ -1067,28 +1065,17 @@ static int mmc_sdio_power_restore(struct mmc_host *host)
* for OLPC SD8686 (which expects a [CMD5,5,3,7] init sequence), and
* harmless in other situations.
*
* With these steps taken, mmc_select_voltage() is also required to
* restore the correct voltage setting of the card.
*/
sdio_reset(host);
mmc_go_idle(host);
mmc_send_if_cond(host, host->ocr_avail);
ret = mmc_send_io_op_cond(host, 0, &ocr);
ret = mmc_send_io_op_cond(host, 0, NULL);
if (ret)
goto out;
if (host->ocr_avail_sdio)
host->ocr_avail = host->ocr_avail_sdio;
rocr = mmc_select_voltage(host, ocr & ~0x7F);
if (!rocr) {
ret = -EINVAL;
goto out;
}
ret = mmc_sdio_init_card(host, rocr, host->card,
ret = mmc_sdio_init_card(host, host->card->ocr, host->card,
mmc_card_keep_power(host));
if (!ret && host->sdio_irqs)
mmc_signal_sdio_irq(host);