[RFC PATCH v2] mmc: suspend MMC also when unbinding

[Wolfram Sang <wsa+renesas@sang-engineering.com>]

When unbinding a MMC host, the card should be suspended. Otherwise,
problems may arise. E.g. the card still expects power-off notifications
but there is no host to send them anymore. Shimoda-san tried disabling
notifications only, but there were issues with his approaches [1] [2].

Here is my take on it, based on the review comments:

a) 'In principle we would like to run the similar operations at "remove"
    as during "system suspend"' [1]
b) 'We want to support a graceful power off sequence or the card...' [2]

So, first, mmc_remove_card() gets improved to mark the card as "not
present" and to call the bus specific suspend() handler.

Then, _mmc_suspend gets extended to recognize another reason of being
called, namely when a card removal happens. Building upon the now
updated mmc_remove_card(), this is the case when the card is flagged as
"not present".

The logic of either sending a notification or sending the card to sleep
gets updated to handle this new reason. Controllers able to do full
power cycles will still do a full power cycle. Controllers which can
only do power cycles in suspend, will send the card to sleep.

All this is for MMC. SD/SDIO are unaffected because they are not using
the 'card present' flag.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

[1] https://patchwork.kernel.org/project/linux-renesas-soc/patch/1602581312-23607-1-git-send-email-yoshihiro.shimoda.uh@renesas.com/
[2] https://patchwork.kernel.org/project/linux-mmc/patch/1605005330-7178-1-git-send-email-yoshihiro.shimoda.uh@renesas.com/
---

Lightly tested with a Renesas R-Car S4 Spider board. It bascially works
as expected. Serious testing postponed until the generic direction of
this is approved :)

 drivers/mmc/core/bus.c |  3 +++
 drivers/mmc/core/mmc.c | 29 +++++++++++++++++++++--------
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/drivers/mmc/core/bus.c b/drivers/mmc/core/bus.c
index 0ddaee0eae54..52704d39c6d5 100644
--- a/drivers/mmc/core/bus.c
+++ b/drivers/mmc/core/bus.c
@@ -403,5 +403,8 @@ void mmc_remove_card(struct mmc_card *card)
 		host->cqe_enabled = false;
 	}
 
+	card->state &= ~MMC_STATE_PRESENT; // TBD: mmc_card_clear_present()
+	host->bus_ops->suspend(host);
+
 	put_device(&card->dev);
 }
diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
index 6a23be214543..2bcf9ee0caa8 100644
--- a/drivers/mmc/core/mmc.c
+++ b/drivers/mmc/core/mmc.c
@@ -32,6 +32,12 @@
 #define MIN_CACHE_EN_TIMEOUT_MS 1600
 #define CACHE_FLUSH_TIMEOUT_MS 30000 /* 30s */
 
+enum mmc_pm_reason {
+	MMC_PM_REASON_SHUTDOWN,
+	MMC_PM_REASON_SUSPEND,
+	MMC_PM_REASON_REMOVAL,
+};
+
 static const unsigned int tran_exp[] = {
 	10000,		100000,		1000000,	10000000,
 	0,		0,		0,		0
@@ -2104,11 +2110,16 @@ static int _mmc_flush_cache(struct mmc_host *host)
 	return err;
 }
 
-static int _mmc_suspend(struct mmc_host *host, bool is_suspend)
+static int _mmc_suspend(struct mmc_host *host, enum mmc_pm_reason reason)
 {
 	int err = 0;
-	unsigned int notify_type = is_suspend ? EXT_CSD_POWER_OFF_SHORT :
-					EXT_CSD_POWER_OFF_LONG;
+	unsigned int notify_type = reason == MMC_PM_REASON_SUSPEND ?
+				   EXT_CSD_POWER_OFF_SHORT : EXT_CSD_POWER_OFF_LONG;
+	bool can_pwr_cycle_now = (host->caps2 & MMC_CAP2_FULL_PWR_CYCLE) ||
+				  ((host->caps2 & MMC_CAP2_FULL_PWR_CYCLE_IN_SUSPEND) &&
+				    reason == MMC_PM_REASON_SUSPEND);
+
+	pr_info("%s: suspend reason %d, can pwr cycle %d\n", mmc_hostname(host), reason, can_pwr_cycle_now);
 
 	mmc_claim_host(host);
 
@@ -2119,9 +2130,9 @@ static int _mmc_suspend(struct mmc_host *host, bool is_suspend)
 	if (err)
 		goto out;
 
+	/* Notify if pwr_cycle is possible or power gets cut because of shutdown */
 	if (mmc_can_poweroff_notify(host->card) &&
-	    ((host->caps2 & MMC_CAP2_FULL_PWR_CYCLE) || !is_suspend ||
-	     (host->caps2 & MMC_CAP2_FULL_PWR_CYCLE_IN_SUSPEND)))
+	    (can_pwr_cycle_now || reason == MMC_PM_REASON_SHUTDOWN))
 		err = mmc_poweroff_notify(host->card, notify_type);
 	else if (mmc_can_sleep(host->card))
 		err = mmc_sleep(host);
@@ -2142,9 +2153,11 @@ static int _mmc_suspend(struct mmc_host *host, bool is_suspend)
  */
 static int mmc_suspend(struct mmc_host *host)
 {
+	enum mmc_pm_reason reason = mmc_card_present(host->card) ?
+				    MMC_PM_REASON_SUSPEND : MMC_PM_REASON_REMOVAL;
 	int err;
 
-	err = _mmc_suspend(host, true);
+	err = _mmc_suspend(host, reason);
 	if (!err) {
 		pm_runtime_disable(&host->card->dev);
 		pm_runtime_set_suspended(&host->card->dev);
@@ -2191,7 +2204,7 @@ static int mmc_shutdown(struct mmc_host *host)
 		err = _mmc_resume(host);
 
 	if (!err)
-		err = _mmc_suspend(host, false);
+		err = _mmc_suspend(host, MMC_PM_REASON_SHUTDOWN);
 
 	return err;
 }
@@ -2215,7 +2228,7 @@ static int mmc_runtime_suspend(struct mmc_host *host)
 	if (!(host->caps & MMC_CAP_AGGRESSIVE_PM))
 		return 0;
 
-	err = _mmc_suspend(host, true);
+	err = _mmc_suspend(host, MMC_PM_REASON_SUSPEND);
 	if (err)
 		pr_err("%s: error %d doing aggressive suspend\n",
 			mmc_hostname(host), err);
-- 
2.45.2