MMC: OMAP: Lazy clock shutdown

MMCA spec says the mmc clock should be kept running for at least
8 cycles after the last RW request. Ensure this with lazy clock
disable after a request, or with an explicit delay before
switching a slot.

Signed-off-by: Jarkko Lavinen <jarkko.lavinen@nokia.com>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>

diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
index 7cc104ce0f07f8b0eec6d5e0dfdd3650e730966e..3d59c5d81b3d1e5e282e046b81250a347640a2fe 100644 (file)
--- a/drivers/mmc/host/omap.c
+++ b/drivers/mmc/host/omap.c
@@ -161,9 +161,38 @@ struct mmc_omap_host {
        wait_queue_head_t       slot_wq;
        int                     nr_slots;
 
+       struct timer_list       clk_timer;
+       spinlock_t              clk_lock;     /* for changing enabled state */
+       unsigned int            fclk_enabled:1;
+
        struct omap_mmc_platform_data *pdata;
 };
 
+void mmc_omap_fclk_offdelay(struct mmc_omap_slot *slot)
+{
+       unsigned long tick_ns;
+
+       if (slot != NULL && slot->host->fclk_enabled && slot->fclk_freq > 0) {
+               tick_ns = (1000000000 + slot->fclk_freq - 1) / slot->fclk_freq;
+               ndelay(8 * tick_ns);
+       }
+}
+
+void mmc_omap_fclk_enable(struct mmc_omap_host *host, unsigned int enable)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(&host->clk_lock, flags);
+       if (host->fclk_enabled != enable) {
+               host->fclk_enabled = enable;
+               if (enable)
+                       clk_enable(host->fclk);
+               else
+                       clk_disable(host->fclk);
+       }
+       spin_unlock_irqrestore(&host->clk_lock, flags);
+}
+
 static void mmc_omap_select_slot(struct mmc_omap_slot *slot, int claimed)
 {
        struct mmc_omap_host *host = slot->host;
@@ -180,32 +209,49 @@ static void mmc_omap_select_slot(struct mmc_omap_slot *slot, int claimed)
        host->mmc = slot->mmc;
        spin_unlock_irqrestore(&host->slot_lock, flags);
 no_claim:
-       clk_enable(host->fclk);
+       del_timer(&host->clk_timer);
+       if (host->current_slot != slot || !claimed)
+               mmc_omap_fclk_offdelay(host->current_slot);
+
        if (host->current_slot != slot) {
+               OMAP_MMC_WRITE(host, CON, slot->saved_con & 0xFC00);
                if (host->pdata->switch_slot != NULL)
                        host->pdata->switch_slot(mmc_dev(slot->mmc), slot->id);
                host->current_slot = slot;
        }
 
-       /* Doing the dummy read here seems to work around some bug
-        * at least in OMAP24xx silicon where the command would not
-        * start after writing the CMD register. Sigh. */
-       OMAP_MMC_READ(host, CON);
+       if (claimed) {
+               mmc_omap_fclk_enable(host, 1);
+
+               /* Doing the dummy read here seems to work around some bug
+                * at least in OMAP24xx silicon where the command would not
+                * start after writing the CMD register. Sigh. */
+               OMAP_MMC_READ(host, CON);
 
-       OMAP_MMC_WRITE(host, CON, slot->saved_con);
+               OMAP_MMC_WRITE(host, CON, slot->saved_con);
+       } else
+               mmc_omap_fclk_enable(host, 0);
 }
 
 static void mmc_omap_start_request(struct mmc_omap_host *host,
                                   struct mmc_request *req);
 
-static void mmc_omap_release_slot(struct mmc_omap_slot *slot)
+static void mmc_omap_release_slot(struct mmc_omap_slot *slot, int clk_enabled)
 {
        struct mmc_omap_host *host = slot->host;
        unsigned long flags;
        int i;
 
        BUG_ON(slot == NULL || host->mmc == NULL);
-       clk_disable(host->fclk);
+
+       if (clk_enabled)
+               /* Keeps clock running for at least 8 cycles on valid freq */
+               mod_timer(&host->clk_timer, jiffies  + HZ/10);
+       else {
+               del_timer(&host->clk_timer);
+               mmc_omap_fclk_offdelay(slot);
+               mmc_omap_fclk_enable(host, 0);
+       }
 
        spin_lock_irqsave(&host->slot_lock, flags);
        /* Check for any pending requests */
@@ -373,7 +419,7 @@ mmc_omap_xfer_done(struct mmc_omap_host *host, struct mmc_data *data)
 
                host->mrq = NULL;
                mmc = host->mmc;
-               mmc_omap_release_slot(host->current_slot);
+               mmc_omap_release_slot(host->current_slot, 1);
                mmc_request_done(mmc, data->mrq);
                return;
        }
@@ -507,7 +553,7 @@ mmc_omap_cmd_done(struct mmc_omap_host *host, struct mmc_command *cmd)
                        mmc_omap_abort_xfer(host, host->data);
                host->mrq = NULL;
                mmc = host->mmc;
-               mmc_omap_release_slot(host->current_slot);
+               mmc_omap_release_slot(host->current_slot, 1);
                mmc_request_done(mmc, cmd->mrq);
        }
 }
@@ -538,7 +584,7 @@ static void mmc_omap_abort_command(struct work_struct *work)
 
                host->mrq = NULL;
                mmc = host->mmc;
-               mmc_omap_release_slot(host->current_slot);
+               mmc_omap_release_slot(host->current_slot, 1);
                mmc_request_done(mmc, cmd->mrq);
        } else
                mmc_omap_cmd_done(host, host->cmd);
@@ -576,6 +622,14 @@ mmc_omap_sg_to_buf(struct mmc_omap_host *host)
                host->buffer_bytes_left = host->total_bytes_left;
 }
 
+static void
+mmc_omap_clk_timer(unsigned long data)
+{
+       struct mmc_omap_host *host = (struct mmc_omap_host *) data;
+
+       mmc_omap_fclk_enable(host, 0);
+}
+
 /* PIO only */
 static void
 mmc_omap_xfer_data(struct mmc_omap_host *host, int write)
@@ -1149,14 +1203,16 @@ static void mmc_omap_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
        struct mmc_omap_slot *slot = mmc_priv(mmc);
        struct mmc_omap_host *host = slot->host;
        int i, dsor;
-
-       dsor = mmc_omap_calc_divisor(mmc, ios);
+       int clk_enabled;
 
        mmc_omap_select_slot(slot, 0);
 
+       dsor = mmc_omap_calc_divisor(mmc, ios);
+
        if (ios->vdd != slot->vdd)
                slot->vdd = ios->vdd;
 
+       clk_enabled = 0;
        switch (ios->power_mode) {
        case MMC_POWER_OFF:
                mmc_omap_set_power(slot, 0, ios->vdd);
@@ -1166,6 +1222,8 @@ static void mmc_omap_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
                mmc_omap_set_power(slot, 1, ios->vdd);
                goto exit;
        case MMC_POWER_ON:
+               mmc_omap_fclk_enable(host, 1);
+               clk_enabled = 1;
                dsor |= 1 << 11;
                break;
        }
@@ -1194,7 +1252,7 @@ static void mmc_omap_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
        }
 
 exit:
-       mmc_omap_release_slot(slot);
+       mmc_omap_release_slot(slot, clk_enabled);
 }
 
 static const struct mmc_host_ops mmc_omap_ops = {
@@ -1335,6 +1393,9 @@ static int __init mmc_omap_probe(struct platform_device *pdev)
        setup_timer(&host->cmd_abort_timer, mmc_omap_cmd_timer,
                    (unsigned long) host);
 
+       spin_lock_init(&host->clk_lock);
+       setup_timer(&host->clk_timer, mmc_omap_clk_timer, (unsigned long) host);
+
        spin_lock_init(&host->dma_lock);
        setup_timer(&host->dma_timer, mmc_omap_dma_timer, (unsigned long) host);
        spin_lock_init(&host->slot_lock);