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Date:	Mon, 22 Sep 2014 11:46:59 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Stephen Warren <swarren@...dotorg.org>,
	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>,
	Alexandre Courbot <acourbot@...dia.com>,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH V2] mmc: don't request CD IRQ until mmc_start_host()

On 09/19/2014 06:56 PM, Stephen Warren wrote:
> 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().
> 
> Ideally, we would solve this by removing the call to
> mmc_gpiod_request_cd_irq() from mmc_gpio_request_cd(). This would match
> mmc_gpio*d*_request_cd(), which already doesn't call
> mmc_gpiod_request_cd_irq(). However, we need to keep the call and make it
> conditional; 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(). Unfortunately, the only way I could
> find to differentiate the two cases was to add an extra parameter to
> mmc_gpio_request_cd() to provide this information.
> 
> 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.
> 
> v2: Rather than completely removing mmc_gpio_request_cd()'s call to
> mmc_gpiod_request_cd_irq(), make the call conditional.

Drivers that call mmc_gpio_request_cd() after mmc_add_host() need
to be changed to call it before mmc_add_host().

However the interim fix is to put the call to mmc_gpiod_request_cd_irq()
into those drivers (mmc_spi.c, sdhci-sirf.c, tmio_mmc_pio.c) rather than
adding request_irq.  That touches far fewer lines and is much easier to
backport / apply to stable.


> ---
>  drivers/mmc/core/host.c            |  2 +-
>  drivers/mmc/core/slot-gpio.c       | 13 +++++++++++--
>  drivers/mmc/host/jz4740_mmc.c      |  3 ++-
>  drivers/mmc/host/mmc_spi.c         |  2 +-
>  drivers/mmc/host/mmci.c            |  2 +-
>  drivers/mmc/host/mvsdio.c          |  2 +-
>  drivers/mmc/host/sdhci-esdhc-imx.c |  3 ++-
>  drivers/mmc/host/sdhci-pxav3.c     |  2 +-
>  drivers/mmc/host/sdhci-sirf.c      |  2 +-
>  drivers/mmc/host/sdhci-spear.c     |  3 ++-
>  drivers/mmc/host/sh_mmcif.c        |  2 +-
>  drivers/mmc/host/tmio_mmc_pio.c    |  2 +-
>  include/linux/mmc/slot-gpio.h      |  2 +-
>  13 files changed, 26 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 95cceae96944..217d6c99c11d 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -374,7 +374,7 @@ int mmc_of_parse(struct mmc_host *host)
>  			if (!(flags & OF_GPIO_ACTIVE_LOW))
>  				gpio_inv_cd = true;
>  
> -			ret = mmc_gpio_request_cd(host, gpio, 0);
> +			ret = mmc_gpio_request_cd(host, gpio, 0, false);
>  			if (ret < 0) {
>  				dev_err(host->parent,
>  					"Failed to request CD GPIO #%d: %d!\n",
> diff --git a/drivers/mmc/core/slot-gpio.c b/drivers/mmc/core/slot-gpio.c
> index 5f89cb83d5f0..b63af8392dc1 100644
> --- a/drivers/mmc/core/slot-gpio.c
> +++ b/drivers/mmc/core/slot-gpio.c
> @@ -176,6 +176,7 @@ EXPORT_SYMBOL(mmc_gpiod_request_cd_irq);
>   * @host: mmc host
>   * @gpio: gpio number requested
>   * @debounce: debounce time in microseconds
> + * @request_irq: Request/enable the IRQ, or defer this until later
>   *
>   * As devm_* managed functions are used in mmc_gpio_request_cd(), client
>   * drivers do not need to explicitly call mmc_gpio_free_cd() for freeing up,
> @@ -191,7 +192,7 @@ EXPORT_SYMBOL(mmc_gpiod_request_cd_irq);
>   * Returns zero on success, else an error.
>   */
>  int mmc_gpio_request_cd(struct mmc_host *host, unsigned int gpio,
> -			unsigned int debounce)
> +			unsigned int debounce, bool request_irq)
>  {
>  	struct mmc_gpio *ctx;
>  	int ret;
> @@ -221,7 +222,15 @@ 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);
> +	/*
> +	 * Ideally, we would never request the IRQ here, but rather rely upon
> +	 * mmc_start_host() calling mmc_gpiod_request_cd_irq(). However, some
> +	 * controller drivers call mmc_gpio_request_cd() after calling
> +	 * mmc_add_host() -> mmc_start_host(), and in that case we need to
> +	 * request the IRQ here, since it won't happen anywhere else.
> +	 */
> +	if (request_irq)
> +		mmc_gpiod_request_cd_irq(host);
>  
>  	return 0;
>  }
> diff --git a/drivers/mmc/host/jz4740_mmc.c b/drivers/mmc/host/jz4740_mmc.c
> index 537d6c7a5ae4..a6eae4764396 100644
> --- a/drivers/mmc/host/jz4740_mmc.c
> +++ b/drivers/mmc/host/jz4740_mmc.c
> @@ -716,7 +716,8 @@ static int jz4740_mmc_request_gpios(struct mmc_host *mmc,
>  		mmc->caps2 |= MMC_CAP2_RO_ACTIVE_HIGH;
>  
>  	if (gpio_is_valid(pdata->gpio_card_detect)) {
> -		ret = mmc_gpio_request_cd(mmc, pdata->gpio_card_detect, 0);
> +		ret = mmc_gpio_request_cd(mmc, pdata->gpio_card_detect, 0,
> +					  false);
>  		if (ret)
>  			return ret;
>  	}
> diff --git a/drivers/mmc/host/mmc_spi.c b/drivers/mmc/host/mmc_spi.c
> index cc8d4a6099cd..60102ce7073b 100644
> --- a/drivers/mmc/host/mmc_spi.c
> +++ b/drivers/mmc/host/mmc_spi.c
> @@ -1433,7 +1433,7 @@ static int mmc_spi_probe(struct spi_device *spi)
>  
>  	if (host->pdata && host->pdata->flags & MMC_SPI_USE_CD_GPIO) {
>  		status = mmc_gpio_request_cd(mmc, host->pdata->cd_gpio,
> -					     host->pdata->cd_debounce);
> +					     host->pdata->cd_debounce, true);
>  		if (status != 0)
>  			goto fail_add_host;
>  	}
> diff --git a/drivers/mmc/host/mmci.c b/drivers/mmc/host/mmci.c
> index e4d470704150..af059635e8d3 100644
> --- a/drivers/mmc/host/mmci.c
> +++ b/drivers/mmc/host/mmci.c
> @@ -1660,7 +1660,7 @@ static int mmci_probe(struct amba_device *dev,
>  
>  	/* If DT, cd/wp gpios must be supplied through it. */
>  	if (!np && gpio_is_valid(plat->gpio_cd)) {
> -		ret = mmc_gpio_request_cd(mmc, plat->gpio_cd, 0);
> +		ret = mmc_gpio_request_cd(mmc, plat->gpio_cd, 0, false);
>  		if (ret)
>  			goto clk_disable;
>  	}
> diff --git a/drivers/mmc/host/mvsdio.c b/drivers/mmc/host/mvsdio.c
> index 6b4c5ad3b393..ab08be46f52f 100644
> --- a/drivers/mmc/host/mvsdio.c
> +++ b/drivers/mmc/host/mvsdio.c
> @@ -772,7 +772,7 @@ static int mvsd_probe(struct platform_device *pdev)
>  		    gpio_is_valid(mvsd_data->gpio_card_detect)) {
>  			ret = mmc_gpio_request_cd(mmc,
>  						  mvsd_data->gpio_card_detect,
> -						  0);
> +						  0, false);
>  			if (ret)
>  				goto out;
>  		} else {
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index ccec0e32590f..311d67b3e10c 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -1068,7 +1068,8 @@ static int sdhci_esdhc_imx_probe(struct platform_device *pdev)
>  	/* card_detect */
>  	switch (boarddata->cd_type) {
>  	case ESDHC_CD_GPIO:
> -		err = mmc_gpio_request_cd(host->mmc, boarddata->cd_gpio, 0);
> +		err = mmc_gpio_request_cd(host->mmc, boarddata->cd_gpio, 0,
> +					  false);
>  		if (err) {
>  			dev_err(mmc_dev(host->mmc),
>  				"failed to request card-detect gpio!\n");
> diff --git a/drivers/mmc/host/sdhci-pxav3.c b/drivers/mmc/host/sdhci-pxav3.c
> index 6f842fb8e6b8..007af74225eb 100644
> --- a/drivers/mmc/host/sdhci-pxav3.c
> +++ b/drivers/mmc/host/sdhci-pxav3.c
> @@ -347,7 +347,7 @@ static int sdhci_pxav3_probe(struct platform_device *pdev)
>  
>  		if (gpio_is_valid(pdata->ext_cd_gpio)) {
>  			ret = mmc_gpio_request_cd(host->mmc, pdata->ext_cd_gpio,
> -						  0);
> +						  0, false);
>  			if (ret) {
>  				dev_err(mmc_dev(host->mmc),
>  					"failed to allocate card detect gpio\n");
> diff --git a/drivers/mmc/host/sdhci-sirf.c b/drivers/mmc/host/sdhci-sirf.c
> index 17004531d089..8e01592007be 100644
> --- a/drivers/mmc/host/sdhci-sirf.c
> +++ b/drivers/mmc/host/sdhci-sirf.c
> @@ -88,7 +88,7 @@ static int sdhci_sirf_probe(struct platform_device *pdev)
>  	 * gets setup in sdhci_add_host() and we oops.
>  	 */
>  	if (gpio_is_valid(priv->gpio_cd)) {
> -		ret = mmc_gpio_request_cd(host->mmc, priv->gpio_cd, 0);
> +		ret = mmc_gpio_request_cd(host->mmc, priv->gpio_cd, 0, true);
>  		if (ret) {
>  			dev_err(&pdev->dev, "card detect irq request failed: %d\n",
>  				ret);
> diff --git a/drivers/mmc/host/sdhci-spear.c b/drivers/mmc/host/sdhci-spear.c
> index 9d535c7336ef..e48372529ef7 100644
> --- a/drivers/mmc/host/sdhci-spear.c
> +++ b/drivers/mmc/host/sdhci-spear.c
> @@ -141,7 +141,8 @@ static int sdhci_probe(struct platform_device *pdev)
>  	 */
>  	if (sdhci->data && sdhci->data->card_int_gpio >= 0) {
>  		ret = mmc_gpio_request_cd(host->mmc,
> -					  sdhci->data->card_int_gpio, 0);
> +					  sdhci->data->card_int_gpio, 0,
> +					  false);
>  		if (ret < 0) {
>  			dev_dbg(&pdev->dev,
>  				"failed to request card-detect gpio%d\n",
> diff --git a/drivers/mmc/host/sh_mmcif.c b/drivers/mmc/host/sh_mmcif.c
> index d11708c815d7..b02e90c52432 100644
> --- a/drivers/mmc/host/sh_mmcif.c
> +++ b/drivers/mmc/host/sh_mmcif.c
> @@ -1464,7 +1464,7 @@ static int sh_mmcif_probe(struct platform_device *pdev)
>  	}
>  
>  	if (pd && pd->use_cd_gpio) {
> -		ret = mmc_gpio_request_cd(mmc, pd->cd_gpio, 0);
> +		ret = mmc_gpio_request_cd(mmc, pd->cd_gpio, 0, false);
>  		if (ret < 0)
>  			goto err_clk;
>  	}
> diff --git a/drivers/mmc/host/tmio_mmc_pio.c b/drivers/mmc/host/tmio_mmc_pio.c
> index faf0924e71cb..ce4d92a43d2c 100644
> --- a/drivers/mmc/host/tmio_mmc_pio.c
> +++ b/drivers/mmc/host/tmio_mmc_pio.c
> @@ -1098,7 +1098,7 @@ int tmio_mmc_host_probe(struct tmio_mmc_host **host,
>  	dev_pm_qos_expose_latency_limit(&pdev->dev, 100);
>  
>  	if (pdata->flags & TMIO_MMC_USE_GPIO_CD) {
> -		ret = mmc_gpio_request_cd(mmc, pdata->cd_gpio, 0);
> +		ret = mmc_gpio_request_cd(mmc, pdata->cd_gpio, 0, true);
>  		if (ret < 0) {
>  			tmio_mmc_host_remove(_host);
>  			return ret;
> diff --git a/include/linux/mmc/slot-gpio.h b/include/linux/mmc/slot-gpio.h
> index d2433381e828..9b0893050cc7 100644
> --- a/include/linux/mmc/slot-gpio.h
> +++ b/include/linux/mmc/slot-gpio.h
> @@ -19,7 +19,7 @@ void mmc_gpio_free_ro(struct mmc_host *host);
>  
>  int mmc_gpio_get_cd(struct mmc_host *host);
>  int mmc_gpio_request_cd(struct mmc_host *host, unsigned int gpio,
> -			unsigned int debounce);
> +			unsigned int debounce, bool request_irq);
>  void mmc_gpio_free_cd(struct mmc_host *host);
>  
>  int mmc_gpiod_request_cd(struct mmc_host *host, const char *con_id,
> 

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