mmc: core: Add support for HS400 re-tuning

HS400 re-tuning must be done in HS200 mode. Add
the ability to switch from HS400 mode to HS200
mode before re-tuning and switch back to HS400
after re-tuning.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/core.h

@@ -88,6 +88,8 @@ void mmc_remove_card_debugfs(struct mmc_card *card);
 void mmc_init_context_info(struct mmc_host *host);
 
 int mmc_execute_tuning(struct mmc_card *card);
+int mmc_hs200_to_hs400(struct mmc_card *card);
+int mmc_hs400_to_hs200(struct mmc_card *card);
 
 #endif
 

drivers/mmc/core/host.c

@@ -340,6 +340,7 @@ void mmc_retune_release(struct mmc_host *host)
 
 int mmc_retune(struct mmc_host *host)
 {
+	bool return_to_hs400 = false;
 	int err;
 
 	if (host->retune_now)
@@ -354,8 +355,24 @@ int mmc_retune(struct mmc_host *host)
 
 	host->doing_retune = 1;
 
+	if (host->ios.timing == MMC_TIMING_MMC_HS400) {
+		err = mmc_hs400_to_hs200(host->card);
+		if (err)
+			goto out;
+
+		return_to_hs400 = true;
+
+		if (host->ops->prepare_hs400_tuning)
+			host->ops->prepare_hs400_tuning(host, &host->ios);
+	}
+
 	err = mmc_execute_tuning(host->card);
+	if (err)
+		goto out;
 
+	if (return_to_hs400)
+		err = mmc_hs200_to_hs400(host->card);
+out:
 	host->doing_retune = 0;
 
 	return err;

drivers/mmc/core/mmc.c

@@ -1092,6 +1092,94 @@ static int mmc_select_hs400(struct mmc_card *card)
 	return 0;
 }
 
+int mmc_hs200_to_hs400(struct mmc_card *card)
+{
+	return mmc_select_hs400(card);
+}
+
+/* Caller must hold re-tuning */
+static int mmc_switch_status(struct mmc_card *card)
+{
+	u32 status;
+	int err;
+
+	err = mmc_send_status(card, &status);
+	if (err)
+		return err;
+
+	return mmc_switch_status_error(card->host, status);
+}
+
+int mmc_hs400_to_hs200(struct mmc_card *card)
+{
+	struct mmc_host *host = card->host;
+	bool send_status = true;
+	unsigned int max_dtr;
+	int err;
+
+	if (host->caps & MMC_CAP_WAIT_WHILE_BUSY)
+		send_status = false;
+
+	/* Reduce frequency to HS */
+	max_dtr = card->ext_csd.hs_max_dtr;
+	mmc_set_clock(host, max_dtr);
+
+	/* Switch HS400 to HS DDR */
+	err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING,
+			   EXT_CSD_TIMING_HS, card->ext_csd.generic_cmd6_time,
+			   true, send_status, true);
+	if (err)
+		goto out_err;
+
+	mmc_set_timing(host, MMC_TIMING_MMC_DDR52);
+
+	if (!send_status) {
+		err = mmc_switch_status(card);
+		if (err)
+			goto out_err;
+	}
+
+	/* Switch HS DDR to HS */
+	err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_BUS_WIDTH,
+			   EXT_CSD_BUS_WIDTH_8, card->ext_csd.generic_cmd6_time,
+			   true, send_status, true);
+	if (err)
+		goto out_err;
+
+	mmc_set_timing(host, MMC_TIMING_MMC_HS);
+
+	if (!send_status) {
+		err = mmc_switch_status(card);
+		if (err)
+			goto out_err;
+	}
+
+	/* Switch HS to HS200 */
+	err = __mmc_switch(card, EXT_CSD_CMD_SET_NORMAL, EXT_CSD_HS_TIMING,
+			   EXT_CSD_TIMING_HS200,
+			   card->ext_csd.generic_cmd6_time, true, send_status,
+			   true);
+	if (err)
+		goto out_err;
+
+	mmc_set_timing(host, MMC_TIMING_MMC_HS200);
+
+	if (!send_status) {
+		err = mmc_switch_status(card);
+		if (err)
+			goto out_err;
+	}
+
+	mmc_set_bus_speed(card);
+
+	return 0;
+
+out_err:
+	pr_err("%s: %s failed, error %d\n", mmc_hostname(card->host),
+	       __func__, err);
+	return err;
+}
+
 /*
  * For device supporting HS200 mode, the following sequence
  * should be done before executing the tuning process.