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    Subject[PATCH 3.16.y-ckt 081/254] mmc: don't request CD IRQ until mmc_start_host()
    Date
    3.16.7-ckt2 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Stephen Warren <swarren@nvidia.com>

    commit d4d11449088ee9aca16fd1884b852b8b73a4bda1 upstream.

    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@arm.linux.org.uk>
    Cc: Adrian Hunter <adrian.hunter@intel.com>
    Cc: Alexandre Courbot <acourbot@nvidia.com>
    Cc: Linus Walleij <linus.walleij@linaro.org>
    Signed-off-by: Stephen Warren <swarren@nvidia.com>
    Acked-by: Adrian Hunter <adrian.hunter@intel.com>
    Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
    Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
    ---
    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;
    --
    2.1.0


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