[PATCH] mmc: Add mmc_force_detect_change_begin / _end functions
Ulf Hansson
ulf.hansson at linaro.org
Mon Aug 22 06:39:34 PDT 2016
On 6 August 2016 at 15:05, Hans de Goede <hdegoede at redhat.com> wrote:
> 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.
Agree, and thanks for the detailed description of the problem!
>
> 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.
Hmm, in the first scan-attempt there will be an SDIO card properly
detected, right!?
The problem occurs when the SDIO func driver gets probed and when it
loads the new firmware, which may happen later or even not at all as
it also depends if the SDIO func driver has been registered.
I am also thinking about the system PM suspend/resume case. In cases
where the SDIO card actually becomes powered off/on in suspend/resume.
In this case, I assume the SDIO card will be re-detected through
mmc_sdio_resume(), although the same sequence as during the SDIO func
driver ->probe() must be repeated (loading firmware etc).
To me it seems like we need a new SDIO func API, to re-initialize the
SDIO card without powering off it first. I guess in the end it will be
quite similar to what you propose, but my point is that I rather make
this a specific SDIO API instead of trying to hook it into the rescan
sequence.
>
> Cc: Icenowy Zheng <icenowy at aosc.xyz>
> Cc: Maxime Ripard <maxime.ripard at free-electrons.com>
> Cc: Chen-Yu Tsai <wens at csie.org>
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> ---
> drivers/mmc/core/core.c | 47 ++++++++++++++++++++++++++++++++++++++++++-----
> include/linux/mmc/host.h | 4 ++++
> 2 files changed, 46 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 8b4dfd4..d850cde 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -1716,8 +1716,11 @@ 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);
>
> @@ -1742,6 +1745,7 @@ 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;
> @@ -1759,6 +1763,11 @@ 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;
> @@ -1907,6 +1916,27 @@ 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;
> @@ -2584,7 +2614,8 @@ 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;
>
> @@ -2601,7 +2632,8 @@ 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;
> @@ -2634,15 +2666,20 @@ 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 45cde8c..e9b3115 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -333,6 +333,8 @@ 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 */
> @@ -408,6 +410,8 @@ 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);
> +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 *);
>
> static inline void mmc_signal_sdio_irq(struct mmc_host *host)
> --
> 2.7.4
>
Kind regards
Uffe
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