Commit fdf492a1 authored by Doug Anderson's avatar Doug Anderson Committed by Chris Ball
Browse files

mmc: dw_mmc: Honor requests to set the clock to 0 



Previously the dw_mmc driver would ignore any requests to disable the
card's clock.  This doesn't seem like a good thing in general, but had
one extra bad side effect in the following situation:
* mmc core would set clk to 400kHz at boot time while scanning
* mmc core would set clk to 0 since no card, but it would be ignored.
* suspend to ram and resume; clocks in the dw_mmc IP block are now 0
  but dw_mmc thinks that they're 400kHz (it ignored the set to 0).
* insert card
* mmc core would set clk to 400kHz which would be considered a no-op.

Note that if there is no card in the slot and we do a suspend/resume
cycle, we _do_ still end up with differences in a dw_mmc register
dump, but the differences are clock related and we've got the clock
disabled both before and after, so this should be OK.

Signed-off-by: default avatarDoug Anderson <dianders@chromium.org>
Signed-off-by: default avatarSeungwon Jeon <tgih.jun@samsung.com>
Signed-off-by: default avatarChris Ball <cjb@laptop.org>
parent e2c63599

drivers/mmc/host/dw_mmc.c

+28 −16
Original line number Diff line number Diff line
@@ -88,6 +88,9 @@ struct idmac_desc { 
 * @queue_node: List node for placing this node in the @queue list of

 *	&struct dw_mci.

 * @clock: Clock rate configured by set_ios(). Protected by host->lock.

 * @__clk_old: The last updated clock with reflecting clock divider.

 *	Keeping track of this helps us to avoid spamming the console

 *	with CONFIG_MMC_CLKGATE.

 * @flags: Random state bits associated with the slot.

 * @id: Number of this slot.

 * @last_detect_state: Most recently observed card detect state.
@@ -105,6 +108,7 @@ struct dw_mci_slot { 
	struct list_head	queue_node;



	unsigned int		clock;

	unsigned int		__clk_old;

	unsigned long		flags;

#define DW_MMC_CARD_PRESENT	0

#define DW_MMC_CARD_NEED_INIT	1
@@ -632,24 +636,31 @@ static void mci_send_cmd(struct dw_mci_slot *slot, u32 cmd, u32 arg) 
static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit)

{

	struct dw_mci *host = slot->host;

	unsigned int clock = slot->clock;

	u32 div;

	u32 clk_en_a;



	if (slot->clock != host->current_speed || force_clkinit) {

		div = host->bus_hz / slot->clock;

		if (host->bus_hz % slot->clock && host->bus_hz > slot->clock)

	if (!clock) {

		mci_writel(host, CLKENA, 0);

		mci_send_cmd(slot,

			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);

	} else if (clock != host->current_speed || force_clkinit) {

		div = host->bus_hz / clock;

		if (host->bus_hz % clock && host->bus_hz > clock)

			/*

			 * move the + 1 after the divide to prevent

			 * over-clocking the card.

			 */

			div += 1;



		div = (host->bus_hz != slot->clock) ? DIV_ROUND_UP(div, 2) : 0;

		div = (host->bus_hz != clock) ? DIV_ROUND_UP(div, 2) : 0;



		if ((clock << div) != slot->__clk_old || force_clkinit)

			dev_info(&slot->mmc->class_dev,

			 "Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ"

			 " div = %d)\n", slot->id, host->bus_hz, slot->clock,

			 div ? ((host->bus_hz / div) >> 1) : host->bus_hz, div);

				 "Bus speed (slot %d) = %dHz (slot req %dHz, actual %dHZ div = %d)\n",

				 slot->id, host->bus_hz, clock,

				 div ? ((host->bus_hz / div) >> 1) :

				 host->bus_hz, div);



		/* disable clock */

		mci_writel(host, CLKENA, 0);
@@ -676,9 +687,12 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot, bool force_clkinit) 
		mci_send_cmd(slot,

			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);



		host->current_speed = slot->clock;

		/* keep the clock with reflecting clock dividor */

		slot->__clk_old = clock << div;

	}



	host->current_speed = clock;



	/* Set the current slot bus width */

	mci_writel(host, CTYPE, (slot->ctype << slot->id));

}
@@ -807,13 +821,11 @@ static void dw_mci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios) 


	mci_writel(slot->host, UHS_REG, regs);



	if (ios->clock) {

	/*

	 * Use mirror of ios->clock to prevent race with mmc

	 * core ios update when finding the minimum.

	 */

	slot->clock = ios->clock;

	}



	if (drv_data && drv_data->set_ios)

		drv_data->set_ios(slot->host, ios);

CRA Git | Maintained and supported by SUSTech CRA and CCSE