From 1ce5a11b0faf0657a65a510ba960554bbfee2410 Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Wed, 30 Mar 2016 16:33:09 +0100
Subject: [PATCH] bcm2835-sdhost: Adjust to core clock changes

The SDHOST block uses the core clock, so previously it has been
necessary to prevent the core clock from changing in order to maintain
performance and prevent accidental SD bus overclocking.

With this patch the sdhost driver is notified of clock changes, allowing
it to delay them while an SD access is outstanding and to delay new SD
accesses while the clock is changing. This feature is disabled in the
case where the core frequency can never change.

Now that the driver copes with changes to the core clock, it is safe
to disable the io_is_busy feature of the on-demand governor.

Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
 drivers/mmc/host/Kconfig          |   1 +
 drivers/mmc/host/bcm2835-sdhost.c | 140 ++++++++++++++++++++++++++++++++------
 2 files changed, 119 insertions(+), 22 deletions(-)

--- a/drivers/mmc/host/Kconfig
+++ b/drivers/mmc/host/Kconfig
@@ -36,6 +36,7 @@ config MMC_BCM2835_PIO_DMA_BARRIER
 config MMC_BCM2835_SDHOST
 	tristate "Support for the SDHost controller on BCM2708/9"
 	depends on MACH_BCM2708 || MACH_BCM2709 || ARCH_BCM2835
+	depends on RASPBERRYPI_FIRMWARE
 	help
 	  This selects the SDHost controller on BCM2835/6.
 
--- a/drivers/mmc/host/bcm2835-sdhost.c
+++ b/drivers/mmc/host/bcm2835-sdhost.c
@@ -50,6 +50,10 @@
 #include <linux/of_dma.h>
 #include <linux/time.h>
 #include <linux/workqueue.h>
+#include <linux/cpufreq.h>
+#include <linux/semaphore.h>
+#include <soc/bcm2835/raspberrypi-firmware.h>
+
 
 #define DRIVER_NAME "sdhost-bcm2835"
 
@@ -136,6 +140,8 @@
 
 #define MHZ 1000000
 
+#define RPI_FIRMWARE_CLOCK_CORE  4
+
 
 struct bcm2835_host {
 	spinlock_t		lock;
@@ -151,7 +157,9 @@ struct bcm2835_host {
 
 	bool			slow_card;	/* Force 11-bit divisor */
 
-	unsigned int		max_clk;	/* Max possible freq */
+	unsigned int		max_clk;	/* Max src clock freq */
+	unsigned int		min_clk;	/* Min src clock freq */
+	unsigned int		cur_clk;	/* Current src clock freq */
 
 	struct tasklet_struct	finish_tasklet;	/* Tasklet structures */
 
@@ -183,6 +191,7 @@ struct bcm2835_host {
 	unsigned int			use_sbc:1;		/* Send CMD23 */
 
 	unsigned int			debug:1;		/* Enable debug output */
+	unsigned int			variable_clock:1;	/* The core clock may change */
 
 	/*DMA part*/
 	struct dma_chan			*dma_chan_rxtx;		/* DMA channel for reads and writes */
@@ -208,6 +217,9 @@ struct bcm2835_host {
 	u32				pio_limit;	/* Maximum block count for PIO (0 = always DMA) */
 
 	u32				sectors;	/* Cached card size in sectors */
+
+	struct notifier_block		cpufreq_nb;	/* The cpufreq callback list item */
+	struct semaphore		cpufreq_semaphore; /* Interlock between SD activity and cpufreq changes */
 };
 
 #if ENABLE_LOG
@@ -227,6 +239,10 @@ static u32 sdhost_log_idx;
 static spinlock_t log_lock;
 static void __iomem *timer_base;
 
+static int bcm2835_sdhost_cpufreq_callback(struct notifier_block *nb,
+					   unsigned long action, void *data);
+static unsigned int get_core_clock(unsigned int mode);
+
 #define LOG_ENTRIES (256*1)
 #define LOG_SIZE (sizeof(LOG_ENTRY_T)*LOG_ENTRIES)
 
@@ -448,20 +464,14 @@ static void bcm2835_sdhost_reset(struct
 
 static void bcm2835_sdhost_set_ios(struct mmc_host *mmc, struct mmc_ios *ios);
 
-static void bcm2835_sdhost_init(struct bcm2835_host *host, int soft)
+static void bcm2835_sdhost_init(struct bcm2835_host *host)
 {
-	pr_debug("bcm2835_sdhost_init(%d)\n", soft);
+	pr_debug("bcm2835_sdhost_init()\n");
 
 	/* Set interrupt enables */
 	host->hcfg = SDHCFG_BUSY_IRPT_EN;
 
 	bcm2835_sdhost_reset_internal(host);
-
-	if (soft) {
-		/* force clock reconfiguration */
-		host->clock = 0;
-		bcm2835_sdhost_set_ios(host->mmc, &host->mmc->ios);
-	}
 }
 
 static void bcm2835_sdhost_wait_transfer_complete(struct bcm2835_host *host)
@@ -1499,10 +1509,10 @@ static irqreturn_t bcm2835_sdhost_irq(in
 	return result;
 }
 
-void bcm2835_sdhost_set_clock(struct bcm2835_host *host, unsigned int clock)
+void bcm2835_sdhost_set_clock(struct bcm2835_host *host)
 {
 	int div = 0; /* Initialized for compiler warning */
-	unsigned int input_clock = clock;
+	unsigned int clock = host->clock;
 
 	if (host->debug)
 		pr_info("%s: set_clock(%d)\n", mmc_hostname(host->mmc), clock);
@@ -1543,17 +1553,17 @@ void bcm2835_sdhost_set_clock(struct bcm
 	    return;
 	}
 
-	div = host->max_clk / clock;
+	div = host->cur_clk / clock;
 	if (div < 2)
 		div = 2;
-	if ((host->max_clk / div) > clock)
+	if ((host->cur_clk / div) > clock)
 		div++;
 	div -= 2;
 
 	if (div > SDCDIV_MAX_CDIV)
 	    div = SDCDIV_MAX_CDIV;
 
-	clock = host->max_clk / (div + 2);
+	clock = host->cur_clk / (div + 2);
 	host->mmc->actual_clock = clock;
 
 	/* Calibrate some delays */
@@ -1561,7 +1571,7 @@ void bcm2835_sdhost_set_clock(struct bcm
 	host->ns_per_fifo_word = (1000000000/clock) *
 		((host->mmc->caps & MMC_CAP_4_BIT_DATA) ? 8 : 32);
 
-	if (clock > input_clock) {
+	if (clock > host->clock) {
 		/* Save the closest value, to make it easier
 		   to reduce in the event of error */
 		host->overclock_50 = (clock/MHZ);
@@ -1587,9 +1597,9 @@ void bcm2835_sdhost_set_clock(struct bcm
 	bcm2835_sdhost_write(host, host->mmc->actual_clock/2, SDTOUT);
 
 	if (host->debug)
-		pr_info("%s: clock=%d -> max_clk=%d, cdiv=%x (actual clock %d)\n",
-			mmc_hostname(host->mmc), input_clock,
-			host->max_clk, host->cdiv, host->mmc->actual_clock);
+		pr_info("%s: clock=%d -> cur_clk=%d, cdiv=%x (actual clock %d)\n",
+			mmc_hostname(host->mmc), host->clock,
+			host->cur_clk, host->cdiv, host->mmc->actual_clock);
 }
 
 static void bcm2835_sdhost_request(struct mmc_host *mmc, struct mmc_request *mrq)
@@ -1638,6 +1648,13 @@ static void bcm2835_sdhost_request(struc
 	    (mrq->data->blocks > host->pio_limit))
 		bcm2835_sdhost_prepare_dma(host, mrq->data);
 
+	if (host->variable_clock &&
+	    (down_killable(&host->cpufreq_semaphore) != 0)) {
+		mrq->cmd->error = -EINTR;
+		mmc_request_done(mmc, mrq);
+		return;
+	}
+
 	spin_lock_irqsave(&host->lock, flags);
 
 	WARN_ON(host->mrq != NULL);
@@ -1687,6 +1704,52 @@ static void bcm2835_sdhost_request(struc
 	spin_unlock_irqrestore(&host->lock, flags);
 }
 
+static int bcm2835_sdhost_cpufreq_callback(struct notifier_block *nb,
+					   unsigned long action, void *data)
+{
+	struct cpufreq_freqs *freq = data;
+	struct bcm2835_host *host;
+
+	host = container_of(nb, struct bcm2835_host, cpufreq_nb);
+
+	if (freq->cpu == 0) {
+		switch (action) {
+		case CPUFREQ_PRECHANGE:
+			if (down_killable(&host->cpufreq_semaphore) != 0)
+				return NOTIFY_BAD;
+			break;
+		case CPUFREQ_POSTCHANGE:
+			if (freq->new > freq->old)
+				host->cur_clk = host->max_clk;
+			else
+				host->cur_clk = host->min_clk;
+			bcm2835_sdhost_set_clock(host);
+			up(&host->cpufreq_semaphore);
+			break;
+		default:
+			break;
+		}
+	}
+	return NOTIFY_OK;
+}
+
+static unsigned int get_core_clock(unsigned int mode)
+{
+	struct rpi_firmware *fw = rpi_firmware_get(NULL);
+	struct {
+		u32 id;
+		u32 val;
+	} packet;
+	int ret;
+
+	packet.id = RPI_FIRMWARE_CLOCK_CORE;
+	ret = rpi_firmware_property(fw, mode, &packet, sizeof(packet));
+	if (ret)
+		return 0;
+
+	return packet.val;
+}
+
 static void bcm2835_sdhost_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
 {
 
@@ -1700,13 +1763,16 @@ static void bcm2835_sdhost_set_ios(struc
 			ios->clock, ios->power_mode, ios->bus_width,
 			ios->timing, ios->signal_voltage, ios->drv_type);
 
+	if (ios->clock && !host->cur_clk)
+		host->cur_clk = get_core_clock(RPI_FIRMWARE_GET_CLOCK_RATE);
+
 	spin_lock_irqsave(&host->lock, flags);
 
 	log_event("IOS<", ios->clock, 0);
 
 	if (!ios->clock || ios->clock != host->clock) {
-		bcm2835_sdhost_set_clock(host, ios->clock);
 		host->clock = ios->clock;
+		bcm2835_sdhost_set_clock(host);
 	}
 
 	/* set bus width */
@@ -1795,7 +1861,7 @@ static void bcm2835_sdhost_tasklet_finis
 			host->overclock_50--;
 			pr_warn("%s: reducing overclock due to errors\n",
 				mmc_hostname(host->mmc));
-			bcm2835_sdhost_set_clock(host,50*MHZ);
+			bcm2835_sdhost_set_clock(host);
 			mrq->cmd->error = -EILSEQ;
 			mrq->cmd->retries = 1;
 		}
@@ -1813,6 +1879,9 @@ static void bcm2835_sdhost_tasklet_finis
 
 	spin_unlock_irqrestore(&host->lock, flags);
 
+	if (host->variable_clock)
+		up(&host->cpufreq_semaphore);
+
 	if (terminate_chan)
 	{
 		int err = dmaengine_terminate_all(terminate_chan);
@@ -1915,10 +1984,10 @@ int bcm2835_sdhost_add_host(struct bcm28
 	setup_timer(&host->timer, bcm2835_sdhost_timeout,
 		    (unsigned long)host);
 
-	bcm2835_sdhost_init(host, 0);
+	bcm2835_sdhost_init(host);
 
 	ret = request_irq(host->irq, bcm2835_sdhost_irq, 0 /*IRQF_SHARED*/,
-				  mmc_hostname(mmc), host);
+			  mmc_hostname(mmc), host);
 	if (ret) {
 		pr_err("%s: failed to request IRQ %d: %d\n",
 		       mmc_hostname(mmc), host->irq, ret);
@@ -1953,6 +2022,7 @@ static int bcm2835_sdhost_probe(struct p
 	struct bcm2835_host *host;
 	struct mmc_host *mmc;
 	const __be32 *addr;
+	unsigned int max_clk;
 	int ret;
 
 	pr_debug("bcm2835_sdhost_probe\n");
@@ -2062,6 +2132,28 @@ static int bcm2835_sdhost_probe(struct p
 	if (ret)
 		goto err;
 
+	/* Query the core clock frequencies */
+	host->min_clk = get_core_clock(RPI_FIRMWARE_GET_MIN_CLOCK_RATE);
+	max_clk = get_core_clock(RPI_FIRMWARE_GET_MAX_CLOCK_RATE);
+	if (max_clk != host->max_clk) {
+		pr_warn("%s: Expected max clock %d, found %d\n",
+			mmc_hostname(mmc), host->max_clk, max_clk);
+		host->max_clk = max_clk;
+	}
+
+	if (host->min_clk != host->max_clk) {
+		host->cpufreq_nb.notifier_call =
+			bcm2835_sdhost_cpufreq_callback;
+		sema_init(&host->cpufreq_semaphore, 1);
+		cpufreq_register_notifier(&host->cpufreq_nb,
+					  CPUFREQ_TRANSITION_NOTIFIER);
+		host->variable_clock = 1;
+		host->cur_clk = 0; /* Get this later */
+	} else {
+		host->variable_clock = 0;
+		host->cur_clk = host->max_clk;
+	}
+
 	platform_set_drvdata(pdev, host);
 
 	pr_debug("bcm2835_sdhost_probe -> OK\n");
@@ -2081,6 +2173,10 @@ static int bcm2835_sdhost_remove(struct
 
 	pr_debug("bcm2835_sdhost_remove\n");
 
+	if (host->variable_clock)
+		cpufreq_unregister_notifier(&host->cpufreq_nb,
+					    CPUFREQ_TRANSITION_NOTIFIER);
+
 	mmc_remove_host(host->mmc);
 
 	bcm2835_sdhost_set_power(host, false);
