On Sat, Oct 30, 2010 at 5:18 AM, Linus Walleij
<linus.walleij@xxxxxxxxxxxxxx> wrote:
> This patch modifies the MMC core code to optionally call the
> set_ios() operation on the driver with the clock frequency set
> to 0 (gate) after a grace period of at least 8 MCLK cycles, then
> restore it (ungate) before any new request. This gives
> the driver the option to shut down the MCI clock to the MMC/SD
> card when the clock frequency is 0, i.e. the core has stated
> that the MCI clock does not need to be generated.
>
> It is inspired by existing clock gating code found in the OMAP
> and Atmel drivers and brings this up to the host abstraction.
> Gating is performed before and after any MMC request.
>
> It exemplifies by implementing this for the MMCI/PL180 MMC/SD
> host controller, but it should be simple to switch OMAP and
> Atmel over to using this instead.
Jaehoon will be test it at samsung SoCs.
To Jaehoon
I wonder, if we apply this patch at MMC, then what's happening with
SDHCI clock gating (from jaehoon patch)
I mean SDHCI already did the clock gating and mmc framework also did
the same things.
Please share the results.
Thank you,
Kyungmin Park
>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxxxxxx>
> ---
> It turned out to be easy to port this code forward to the
> current kernel. I'll be hacking some MMCI support code on my
> flight and test it when I get back to Sweden.
>
> In the meantime, Sukumar can you test if this can be made
> to work for you on the OMAP?
> ---
> drivers/mmc/core/Kconfig | 11 +++
> drivers/mmc/core/core.c | 39 +++++++++-
> drivers/mmc/core/core.h | 2 +
> drivers/mmc/core/debugfs.c | 5 +
> drivers/mmc/core/host.c | 187 +++++++++++++++++++++++++++++++++++++++++++-
> drivers/mmc/core/host.h | 4 +
> include/linux/mmc/host.h | 10 +++
> 7 files changed, 256 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/core/Kconfig b/drivers/mmc/core/Kconfig
> index bb22ffd..1018ccc1 100644
> --- a/drivers/mmc/core/Kconfig
> +++ b/drivers/mmc/core/Kconfig
> @@ -16,3 +16,14 @@ config MMC_UNSAFE_RESUME
>
> This option sets a default which can be overridden by the
> module parameter "removable=0" or "removable=1".
> +
> +config MMC_CLKGATE
> + bool "MMC host clock gating (EXPERIMENTAL)"
> + depends on EXPERIMENTAL
> + help
> + This will attempt to agressively gate the clock to the MMC card.
> + This is done to save power due to gating off the logic and bus
> + noise when the MMC card is not in use. Your host driver has to
> + support handling this in order for it to be of any use.
> +
> + If unsure, say N.
> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
> index 8f86d70..e74e767 100644
> --- a/drivers/mmc/core/core.c
> +++ b/drivers/mmc/core/core.c
> @@ -130,6 +130,8 @@ void mmc_request_done(struct mmc_host *host, struct mmc_request *mrq)
>
> if (mrq->done)
> mrq->done(mrq);
> +
> + mmc_host_clk_gate(host);
> }
> }
>
> @@ -190,6 +192,7 @@ mmc_start_request(struct mmc_host *host, struct mmc_request *mrq)
> mrq->stop->mrq = mrq;
> }
> }
> + mmc_host_clk_ungate(host);
> host->ops->request(host, mrq);
> }
>
> @@ -296,7 +299,7 @@ void mmc_set_data_timeout(struct mmc_data *data, const struct mmc_card *card)
>
> timeout_us = data->timeout_ns / 1000;
> timeout_us += data->timeout_clks * 1000 /
> - (card->host->ios.clock / 1000);
> + (mmc_host_clk_rate(card->host) / 1000);
>
> if (data->flags & MMC_DATA_WRITE)
> /*
> @@ -641,6 +644,40 @@ void mmc_set_clock(struct mmc_host *host, unsigned int hz)
> mmc_set_ios(host);
> }
>
> +#ifdef CONFIG_MMC_CLKGATE
> +/*
> + * This gates the clock by setting it to 0 Hz.
> + */
> +void mmc_gate_clock(struct mmc_host *host)
> +{
> + host->clk_old = host->ios.clock;
> + host->ios.clock = 0;
> + host->clk_gated = true;
> + mmc_set_ios(host);
> +}
> +
> +/*
> + * This restores the clock from gating by using the cached
> + * clock value.
> + */
> +void mmc_ungate_clock(struct mmc_host *host)
> +{
> + /*
> + * We should previously have gated the clock, so the clock
> + * shall be 0 here!
> + * The clock may however be 0 during intialization,
> + * when some request operations are performed before setting
> + * the frequency. When ungate is requested in that situation
> + * we just ignore the call.
> + */
> + if (host->clk_old) {
> + BUG_ON(host->ios.clock);
> + mmc_set_clock(host, host->clk_old);
> + }
> + host->clk_gated = false;
> +}
> +#endif
> +
> /*
> * Change the bus mode (open drain/push-pull) of a host.
> */
> diff --git a/drivers/mmc/core/core.h b/drivers/mmc/core/core.h
> index 77240cd..9972808 100644
> --- a/drivers/mmc/core/core.h
> +++ b/drivers/mmc/core/core.h
> @@ -33,6 +33,8 @@ void mmc_init_erase(struct mmc_card *card);
>
> void mmc_set_chip_select(struct mmc_host *host, int mode);
> void mmc_set_clock(struct mmc_host *host, unsigned int hz);
> +void mmc_gate_clock(struct mmc_host *host);
> +void mmc_ungate_clock(struct mmc_host *host);
> void mmc_set_bus_mode(struct mmc_host *host, unsigned int mode);
> void mmc_set_bus_width(struct mmc_host *host, unsigned int width);
> void mmc_set_bus_width_ddr(struct mmc_host *host, unsigned int width,
> diff --git a/drivers/mmc/core/debugfs.c b/drivers/mmc/core/debugfs.c
> index eed1405..998797e 100644
> --- a/drivers/mmc/core/debugfs.c
> +++ b/drivers/mmc/core/debugfs.c
> @@ -183,6 +183,11 @@ void mmc_add_host_debugfs(struct mmc_host *host)
> &mmc_clock_fops))
> goto err_node;
>
> +#ifdef CONFIG_MMC_CLKGATE
> + if (!debugfs_create_u32("clk_delay", (S_IRUSR | S_IWUSR),
> + root, &host->clk_delay))
> + goto err_node;
> +#endif
> return;
>
> err_node:
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 10b8af2..dc39605 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -3,6 +3,7 @@
> *
> * Copyright (C) 2003 Russell King, All Rights Reserved.
> * Copyright (C) 2007-2008 Pierre Ossman
> + * Copyright (C) 2010 Linus Walleij
> *
> * This program is free software; you can redistribute it and/or modify
> * it under the terms of the GNU General Public License version 2 as
> @@ -50,6 +51,187 @@ void mmc_unregister_host_class(void)
> static DEFINE_IDR(mmc_host_idr);
> static DEFINE_SPINLOCK(mmc_host_lock);
>
> +#ifdef CONFIG_MMC_CLKGATE
> +
> +/*
> + * Enabling clock gating will make the core call out to the host
> + * once up and once down when it performs a request or card operation
> + * intermingled in any fashion. The driver will see this through
> + * set_ios() operations with ios.clock field set to 0 to gate
> + * (disable) the block clock, and to the old frequency to enable
> + * it again.
> + */
> +static void mmc_host_clk_gate_delayed(struct mmc_host *host)
> +{
> + unsigned long tick_ns;
> + unsigned long freq = host->ios.clock;
> + unsigned long flags;
> + int users;
> +
> + if (!freq) {
> + pr_err("%s: frequency set to 0 in disable function, "
> + "this means the clock is already disabled.\n",
> + mmc_hostname(host));
> + return;
> + }
> + /*
> + * New requests may have appeared while we were scheduling,
> + * then there is no reason to delay the check before
> + * clk_disable().
> + */
> + spin_lock_irqsave(&host->clk_lock, flags);
> + users = host->clk_requests;
> + /*
> + * Delay 8 bus cycles (from MMC spec) before attempting
> + * to disable the MMCI block clock. The reference count
> + * may have gone up again after this delay due to
> + * rescheduling!
> + */
> + if (!users) {
> + spin_unlock_irqrestore(&host->clk_lock, flags);
> + tick_ns = DIV_ROUND_UP(1000000000, freq);
> + ndelay(host->clk_delay * tick_ns);
> + } else {
> + /* New users appeared while waiting for this work */
> + host->clk_pending_gate = false;
> + spin_unlock_irqrestore(&host->clk_lock, flags);
> + return;
> + }
> + spin_lock_irqsave(&host->clk_lock, flags);
> + if (!host->clk_requests) {
> + spin_unlock_irqrestore(&host->clk_lock, flags);
> + /* this will set host->ios.clock to 0 */
> + mmc_gate_clock(host);
> + spin_lock_irqsave(&host->clk_lock, flags);
> + pr_debug("%s: disabled MCI clock\n",
> + mmc_hostname(host));
> + }
> + host->clk_pending_gate = false;
> + spin_unlock_irqrestore(&host->clk_lock, flags);
> +}
> +
> +/*
> + * Internal work. Work to disable the clock at some later point.
> + */
> +static void mmc_host_clk_gate_work(struct work_struct *work)
> +{
> + struct mmc_host *host = container_of(work, struct mmc_host,
> + clk_disable_work);
> +
> + mmc_host_clk_gate_delayed(host);
> +}
> +
> +/*
> + * mmc_host_clk_ungate - make sure the host ios.clock is
> + * restored to some non-zero value past this call.
> + * @host: host to ungate.
> + *
> + * Increase clock reference count and ungate clock if first user.
> + */
> +void mmc_host_clk_ungate(struct mmc_host *host)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&host->clk_lock, flags);
> + if (host->clk_gated) {
> + spin_unlock_irqrestore(&host->clk_lock, flags);
> + mmc_ungate_clock(host);
> + spin_lock_irqsave(&host->clk_lock, flags);
> + pr_debug("%s: ungated MCI clock\n",
> + mmc_hostname(host));
> + }
> + host->clk_requests++;
> + spin_unlock_irqrestore(&host->clk_lock, flags);
> +}
> +
> +/*
> + * mmc_host_clk_gate - call the host driver with ios.clock
> + * set to zero as often as possible so as to make it
> + * possible to gate off hardware MCI clocks.
> + * @host: host to gate.
> + *
> + * Decrease clock reference count and schedule disablement of clock.
> + */
> +void mmc_host_clk_gate(struct mmc_host *host)
> +{
> + unsigned long flags;
> +
> + spin_lock_irqsave(&host->clk_lock, flags);
> + host->clk_requests--;
> + if (!host->clk_requests) {
> + host->clk_pending_gate = true;
> + schedule_work(&host->clk_disable_work);
> + }
> + spin_unlock_irqrestore(&host->clk_lock, flags);
> +}
> +
> +/*
> + * mmc_host_clk_rate - get current clock frequency setting no matter
> + * whether it's gated or not.
> + * @host: host to get the clock frequency for.
> + */
> +unsigned int mmc_host_clk_rate(struct mmc_host *host)
> +{
> + unsigned long freq;
> + unsigned long flags;
> +
> + spin_lock_irqsave(&host->clk_lock, flags);
> + if (host->clk_gated)
> + freq = host->clk_old;
> + else
> + freq = host->ios.clock;
> + spin_unlock_irqrestore(&host->clk_lock, flags);
> + return freq;
> +}
> +
> +/*
> + * mmc_host_clk_init - set up clock gating code
> + * @host: host with potential hardware clock to control
> + */
> +static inline void mmc_host_clk_init(struct mmc_host *host)
> +{
> + host->clk_requests = 0;
> + host->clk_delay = 8; /* hold MCI clock in 8 cycles by default */
> + host->clk_gated = false;
> + host->clk_pending_gate = false;
> + INIT_WORK(&host->clk_disable_work, mmc_host_clk_gate_work);
> + spin_lock_init(&host->clk_lock);
> +}
> +
> +/*
> + * mmc_host_clk_exit - shut down clock gating code
> + * @host: host with potential hardware clock to control
> + */
> +static inline void mmc_host_clk_exit(struct mmc_host *host)
> +{
> + if (cancel_work_sync(&host->clk_disable_work))
> + mmc_host_clk_gate_delayed(host);
> + BUG_ON(host->clk_requests > 0);
> +}
> +
> +#else
> +inline void mmc_host_clk_ungate(struct mmc_host *host)
> +{
> +}
> +
> +inline void mmc_host_clk_gate(struct mmc_host *host)
> +{
> +}
> +
> +inline unsigned int mmc_host_clk_rate(struct mmc_host *host)
> +{
> + return host->ios.clock;
> +}
> +
> +static inline void mmc_host_clk_init(struct mmc_host *host)
> +{
> +}
> +
> +static inline void mmc_host_clk_exit(struct mmc_host *host)
> +{
> +}
> +#endif
> +
> /**
> * mmc_alloc_host - initialise the per-host structure.
> * @extra: sizeof private data structure
> @@ -82,6 +264,8 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
> host->class_dev.class = &mmc_host_class;
> device_initialize(&host->class_dev);
>
> + mmc_host_clk_init(host);
> +
> spin_lock_init(&host->lock);
> init_waitqueue_head(&host->wq);
> INIT_DELAYED_WORK(&host->detect, mmc_rescan);
> @@ -163,6 +347,8 @@ void mmc_remove_host(struct mmc_host *host)
> device_del(&host->class_dev);
>
> led_trigger_unregister_simple(host->led);
> +
> + mmc_host_clk_exit(host);
> }
>
> EXPORT_SYMBOL(mmc_remove_host);
> @@ -183,4 +369,3 @@ void mmc_free_host(struct mmc_host *host)
> }
>
> EXPORT_SYMBOL(mmc_free_host);
> -
> diff --git a/drivers/mmc/core/host.h b/drivers/mmc/core/host.h
> index 8c87e11..0529b1f 100644
> --- a/drivers/mmc/core/host.h
> +++ b/drivers/mmc/core/host.h
> @@ -10,9 +10,13 @@
> */
> #ifndef _MMC_CORE_HOST_H
> #define _MMC_CORE_HOST_H
> +#include <linux/mmc/host.h>
>
> int mmc_register_host_class(void);
> void mmc_unregister_host_class(void);
> +void mmc_host_clk_ungate(struct mmc_host *host);
> +void mmc_host_clk_gate(struct mmc_host *host);
> +unsigned int mmc_host_clk_rate(struct mmc_host *host);
>
> void mmc_host_deeper_disable(struct work_struct *work);
>
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 6d87f68..c38c400 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -171,6 +171,16 @@ struct mmc_host {
>
> mmc_pm_flag_t pm_caps; /* supported pm features */
>
> +#ifdef CONFIG_MMC_CLKGATE
> + int clk_requests; /* internal reference counter */
> + unsigned int clk_delay; /* number of MCI clk hold cycles */
> + bool clk_gated; /* clock gated */
> + bool clk_pending_gate; /* pending clock gating */
> + struct work_struct clk_disable_work; /* delayed clock disablement */
> + unsigned int clk_old; /* old clock value cache */
> + spinlock_t clk_lock; /* lock for clk fields */
> +#endif
> +
> /* host specific block data */
> unsigned int max_seg_size; /* see blk_queue_max_segment_size */
> unsigned short max_segs; /* see blk_queue_max_segments */
> --
> 1.7.2.3
>
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