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Message-Id: <1411401462-1509-1-git-send-email-swarren@wwwdotorg.org>
Date: Mon, 22 Sep 2014 09:57:42 -0600
From: Stephen Warren <swarren@...dotorg.org>
To: Chris Ball <chris@...ntf.net>, Ulf Hansson <ulf.hansson@...aro.org>
Cc: linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
Stephen Warren <swarren@...dia.com>,
Russell King <linux@....linux.org.uk>,
Adrian Hunter <adrian.hunter@...el.com>,
Alexandre Courbot <acourbot@...dia.com>,
Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH] mmc: don't request CD IRQ until mmc_start_host()
From: Stephen Warren <swarren@...dia.com>
As soon as the CD IRQ is requested, it can trigger, since it's an
externally controlled event. If it does, delayed_work host->detect will
be scheduled.
Many host controller probe()s are roughly structured as:
*_probe() {
host = sdhci_pltfm_init();
mmc_of_parse(host->mmc);
rc = sdhci_add_host(host);
if (rc) {
sdhci_pltfm_free();
return rc;
}
In 3.17, CD IRQs can are enabled quite early via *_probe() ->
mmc_of_parse() -> mmc_gpio_request_cd() -> mmc_gpiod_request_cd_irq().
Note that in linux-next, mmc_of_parse() calls mmc_gpio*d*_request_cd()
rather than mmc_gpio_request_cd(), and mmc_gpio*d*_request_cd() doesn't
call mmc_gpiod_request_cd_irq(). However, this issue still exists if
mmc_gpio_request_cd() is called directly before mmc_start_host().
sdhci_add_host() may fail part way through (e.g. due to deferred
probe for a vmmc regulator), and sdhci_pltfm_free() does nothing to
unrequest the CD IRQ nor cancel the delayed_work. sdhci_pltfm_free() is
coded to assume that if sdhci_add_host() failed, then the delayed_work
cannot (or should not) have been triggered.
This can lead to the following with CONFIG_DEBUG_OBJECTS_* enabled, when
kfree(host) is eventually called inside sdhci_pltfm_free():
WARNING: CPU: 2 PID: 6 at lib/debugobjects.c:263 debug_print_object+0x8c/0xb4()
ODEBUG: free active (active state 0) object type: timer_list hint: delayed_work_timer_fn+0x0/0x18
The object being complained about is host->detect.
There's no need to request the CD IRQ so early; mmc_start_host() already
requests it. For most SDHCI hosts at least, the typical call path that
does this is: *_probe() -> sdhci_add_host() -> mmc_add_host() ->
mmc_start_host(). Therefore, remove the call to mmc_gpiod_request_cd_irq()
from mmc_gpio_request_cd(). This also matches mmc_gpio*d*_request_cd(),
which already doesn't call mmc_gpiod_request_cd_irq().
However, some host controller drivers call mmc_gpio_request_cd() after
mmc_start_host() has already been called, and assume that this will also
call mmc_gpiod_request_cd_irq(). Update those drivers to explicitly call
mmc_gpiod_request_cd_irq() themselves. Ideally, these drivers should be
modified to move their call to mmc_gpio_request_cd() before their call
to mmc_add_host(). However that's too large a change for stable.
This solves the problem (eliminates the kernel error message above),
since it guarantees that the IRQ can't trigger before mmc_start_host()
is called.
The critical point here is that once sdhci_add_host() calls
mmc_add_host() -> mmc_start_host(), sdhci_add_host() is coded not to
fail. In other words, if there's a chance that mmc_start_host() may have
been called, and CD IRQs triggered, and the delayed_work scheduled,
sdhci_add_host() won't fail, and so cleanup is no longer via
sdhci_pltfm_free() (which doesn't free the IRQ or cancel the work queue)
but instead must be via sdhci_remove_host(), which calls mmc_remove_host()
-> mmc_stop_host(), which does free the IRQ and cancel the work queue.
CC: Russell King <linux@....linux.org.uk>
Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Alexandre Courbot <acourbot@...dia.com>
Cc: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Stephen Warren <swarren@...dia.com>
---
Note: This is a patch for v3.17 (and perhaps earlier); linux-next doesn't
have this problem due to other code re-structing. However, I think those
patches are too large to backport.
v3: Explicitly call mmc_gpiod_request_cd_irq() from drivers that call
mmc_gpio_request_cd() after calling mmc_add_host(), rather than modifying
the function signature of mmc_gpio_request_cd().
v2: Rather than completely removing mmc_gpio_request_cd()'s call to
mmc_gpiod_request_cd_irq(), make the call conditional.
---
drivers/mmc/core/slot-gpio.c | 2 --
drivers/mmc/host/mmc_spi.c | 1 +
drivers/mmc/host/sdhci-sirf.c | 1 +
drivers/mmc/host/tmio_mmc_pio.c | 1 +
4 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/mmc/core/slot-gpio.c b/drivers/mmc/core/slot-gpio.c
index 5f89cb83d5f0..187f48a5795a 100644
--- a/drivers/mmc/core/slot-gpio.c
+++ b/drivers/mmc/core/slot-gpio.c
@@ -221,8 +221,6 @@ int mmc_gpio_request_cd(struct mmc_host *host, unsigned int gpio,
ctx->override_cd_active_level = true;
ctx->cd_gpio = gpio_to_desc(gpio);
- mmc_gpiod_request_cd_irq(host);
-
return 0;
}
EXPORT_SYMBOL(mmc_gpio_request_cd);
diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c
index cc8d4a6099cd..e4a07546f8b6 100644
--- a/drivers/mmc/host/mmc_spi.c
+++ b/drivers/mmc/host/mmc_spi.c
@@ -1436,6 +1436,7 @@ static int mmc_spi_probe(struct spi_device *spi)
host->pdata->cd_debounce);
if (status != 0)
goto fail_add_host;
+ mmc_gpiod_request_cd_irq(mmc);
}
if (host->pdata && host->pdata->flags & MMC_SPI_USE_RO_GPIO) {
diff --git a/drivers/mmc/host/sdhci-sirf.c b/drivers/mmc/host/sdhci-sirf.c
index 17004531d089..b6db259aea9e 100644
--- a/drivers/mmc/host/sdhci-sirf.c
+++ b/drivers/mmc/host/sdhci-sirf.c
@@ -94,6 +94,7 @@ static int sdhci_sirf_probe(struct platform_device *pdev)
ret);
goto err_request_cd;
}
+ mmc_gpiod_request_cd_irq(host->mmc);
}
return 0;
diff --git a/drivers/mmc/host/tmio_mmc_pio.c b/drivers/mmc/host/tmio_mmc_pio.c
index faf0924e71cb..59d9a7249b2e 100644
--- a/drivers/mmc/host/tmio_mmc_pio.c
+++ b/drivers/mmc/host/tmio_mmc_pio.c
@@ -1103,6 +1103,7 @@ int tmio_mmc_host_probe(struct tmio_mmc_host **host,
tmio_mmc_host_remove(_host);
return ret;
}
+ mmc_gpiod_request_cd_irq(mmc);
}
*host = _host;
--
1.9.1
--
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