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>

1 files changed, 75 insertions, 14 deletions

diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
index 7cc104ce0f07..3d59c5d81b3d 100644
--- 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);