Commit ce69d37b authored by Ulf Hansson's avatar Ulf Hansson Committed by Chris Ball
Browse files

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: default avatarUlf Hansson <ulf.hansson@linaro.org>
Signed-off-by: default avatarChris Ball <cjb@laptop.org>
parent 69041150

drivers/mmc/core/core.c

+11 −20
Original line number Diff line number Diff line
@@ -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;

drivers/mmc/core/mmc.c

+0 −1
Original line number Diff line number Diff line
@@ -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);

drivers/mmc/core/sd.c

+0 −1
Original line number Diff line number Diff line
@@ -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);

drivers/mmc/core/sdio.c

+2 −15
Original line number Diff line number Diff line
@@ -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);

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