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Subject[PATCH 2/2] mmc: Add mmc_force_detect_change_begin / _end functions
Date
From: Hans de Goede <hdegoede@redhat.com>

Some sdio devices have a multiple stage bring-up process. Specifically
the esp8089 (for which an out of tree driver is available) loads firmware
on the first call to its sdio-drivers' probe function and then resets
the device causing it to reboot from its RAM with the new firmware.

When this sdio device reboots it comes back up in 1 bit 400 KHz mode
again, and we need to walk through the whole ios negatiation and sdio setup
again.

There are 2 problems with this:

1) Typically these devices are soldered onto some (ARM) tablet / SBC
PCB and as such are described in devicetree as "non-removable", which
causes the mmc-core to scan them only once and not poll for the device
dropping of the bus. Normally this is the right thing todo but in the
eso8089 example we need the mmc-core to notice the module has disconnected
(since it is now in 1 bit mode again it will not talk to the host in 4 bit
mode). This can be worked around by using "broken-cd" in devicetree
instead of "non-removable", but that is not a proper fix since the device
really is non-removable.

2) When the mmc-core detects the device has disconnected it will poweroff
the device, causing the RAM loaded firmware to be lost. This can be worked
around in devicetree by using regulator-always-on (and avoiding the use of
mmc-pwrseq), but again that is more of a hack then a proper fix.

This commmit fixes 1) by adding a mmc_force_detect_change function which
will cause scanning for device removal / insertion until a new device is
detected. 2) Is fixed by a keep_power flag to the mmc_force_detect_change
function which when set causes the mmc-core to keep the power to the device
on during the rescan.

Cc: Icenowy Zheng <icenowy@aosc.xyz>
Cc: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
drivers/mmc/core/core.c | 47 ++++++++++++++++++++++++++++++++++++++++++-----
include/linux/mmc/host.h | 7 +++++++
2 files changed, 49 insertions(+), 5 deletions(-)

diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
index 26431267a3e2..103badde910b 100644
--- a/drivers/mmc/core/core.c
+++ b/drivers/mmc/core/core.c
@@ -1620,8 +1620,11 @@ int mmc_select_drive_strength(struct mmc_card *card, unsigned int max_dtr,
*/
void mmc_power_up(struct mmc_host *host, u32 ocr)
{
- if (host->ios.power_mode == MMC_POWER_ON)
+ if (host->ios.power_mode == MMC_POWER_ON) {
+ if (host->ios.clock == 0)
+ goto set_clock;
return;
+ }

mmc_pwrseq_pre_power_on(host);

@@ -1646,6 +1649,7 @@ void mmc_power_up(struct mmc_host *host, u32 ocr)

mmc_pwrseq_post_power_on(host);

+set_clock:
host->ios.clock = host->f_init;

host->ios.power_mode = MMC_POWER_ON;
@@ -1663,6 +1667,11 @@ void mmc_power_off(struct mmc_host *host)
if (host->ios.power_mode == MMC_POWER_OFF)
return;

+ if (host->rescan_keep_power) {
+ mmc_set_clock(host, 0);
+ return;
+ }
+
mmc_pwrseq_power_off(host);

host->ios.clock = 0;
@@ -1804,6 +1813,27 @@ void mmc_detect_change(struct mmc_host *host, unsigned long delay)
}
EXPORT_SYMBOL(mmc_detect_change);

+/**
+ * mmc_force_detect_change - force rescanning of a MMC socket even if
+ * it is non-removable
+ * @host: host to rescan
+ * @delay: optional delay to wait before detection (jiffies)
+ * @keep_power: if set do not turn of vdd / call pwrseq_off during rescan
+ *
+ * MMC drivers which need non-removable sdio devices to be rescanned
+ * (e.g. because the device reboots its fw after a firmware upload),
+ * can call this to force scanning the MMC socket for changes, even
+ * if it is non-removable.
+ */
+void mmc_force_detect_change(struct mmc_host *host, unsigned long delay,
+ bool keep_power)
+{
+ host->rescan_force = 1;
+ host->rescan_keep_power = keep_power;
+ _mmc_detect_change(host, delay, false);
+}
+EXPORT_SYMBOL(mmc_force_detect_change);
+
void mmc_init_erase(struct mmc_card *card)
{
unsigned int sz;
@@ -2566,7 +2596,8 @@ void mmc_rescan(struct work_struct *work)
return;

/* If there is a non-removable card registered, only scan once */
- if (!mmc_card_is_removable(host) && host->rescan_entered)
+ if (!mmc_card_is_removable(host) && host->rescan_entered &&
+ !host->rescan_force)
return;
host->rescan_entered = 1;

@@ -2583,7 +2614,8 @@ void mmc_rescan(struct work_struct *work)
* if there is a _removable_ card registered, check whether it is
* still present
*/
- if (host->bus_ops && !host->bus_dead && mmc_card_is_removable(host))
+ if (host->bus_ops && !host->bus_dead &&
+ (mmc_card_is_removable(host) || host->rescan_force))
host->bus_ops->detect(host);

host->detect_change = 0;
@@ -2616,15 +2648,20 @@ void mmc_rescan(struct work_struct *work)
}

for (i = 0; i < ARRAY_SIZE(freqs); i++) {
- if (!mmc_rescan_try_freq(host, max(freqs[i], host->f_min)))
+ if (!mmc_rescan_try_freq(host, max(freqs[i], host->f_min))) {
+ if (host->rescan_force) {
+ host->rescan_force = 0;
+ host->rescan_keep_power = 0;
+ }
break;
+ }
if (freqs[i] <= host->f_min)
break;
}
mmc_release_host(host);

out:
- if (host->caps & MMC_CAP_NEEDS_POLL)
+ if ((host->caps & MMC_CAP_NEEDS_POLL) || host->rescan_force)
mmc_schedule_delayed_work(&host->detect, HZ);
}

diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index ebd1cebbef0c..d56d79867bbd 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -338,6 +338,8 @@ struct mmc_host {

int rescan_disable; /* disable card detection */
int rescan_entered; /* used with nonremovable devices */
+ int rescan_force; /* force rescan of (nonremovable) devices */
+ int rescan_keep_power; /* Do not power off card */

int need_retune; /* re-tuning is needed */
int hold_retune; /* hold off re-tuning */
@@ -420,6 +422,11 @@ int mmc_power_save_host(struct mmc_host *host);
int mmc_power_restore_host(struct mmc_host *host);

void mmc_detect_change(struct mmc_host *, unsigned long delay);
+
+/* HdG: HACK HACK HACK do not upstream */
+#define MMC_HAS_FORCE_DETECT_CHANGE
+void mmc_force_detect_change(struct mmc_host *host, unsigned long delay,
+ bool keep_power);
void mmc_request_done(struct mmc_host *, struct mmc_request *);
void mmc_command_done(struct mmc_host *host, struct mmc_request *mrq);

--
2.11.0
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