mmc: sd: add support for tuning during uhs initialization

Host Controller needs tuning during initialization to operate SDR50
and SDR104 UHS-I cards. Whether SDR50 mode actually needs tuning is
indicated by bit 45 of the Host Controller Capabilities register.
A new command CMD19 has been defined in the Physical Layer spec
v3.01 to request the card to send tuning pattern.

We enable Buffer Read Ready interrupt at the very begining of tuning
procedure, because that is the only interrupt generated by the Host
Controller during tuning. We program the block size to 64 in the
Block Size register. We make sure that DMA Enable and Multi Block
Select in the Transfer Mode register are set to 0 before actually
sending CMD19. The tuning block is sent by the card to the Host
Controller using DAT lines, so we set Data Present Select (bit 5) in
the Command register. The Host Controller is responsible for doing
the verfication of tuning block sent by the card at the hardware
level. After sending CMD19, we wait for Buffer Read Ready interrupt.
In case we don't receive an interrupt after the specified timeout
value, we fall back on fixed sampling clock by setting Execute
Tuning (bit 6) and Sampling Clock Select (bit 7) of Host Control2
register to 0. Before exiting the tuning procedure, we disable Buffer
Read Ready interrupt and re-enable other interrupts.

Tested by Zhangfei Gao with a Toshiba uhs card and general hs card,
on mmp2 in SDMA mode.

Signed-off-by: Arindam Nath <arindam.nath@amd.com>
Reviewed-by: Philip Rakity <prakity@marvell.com>
Tested-by: Philip Rakity <prakity@marvell.com>
Acked-by: Zhangfei Gao <zhangfei.gao@marvell.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

1 files changed, 167 insertions, 1 deletions

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index 2a15aad2eba5..8a56eacea34d 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -38,6 +38,8 @@
 #define SDHCI_USE_LEDS_CLASS
 #endif
 
+#define MAX_TUNING_LOOP 40
+
 static unsigned int debug_quirks = 0;
 
 static void sdhci_finish_data(struct sdhci_host *);
@@ -968,7 +970,9 @@ static void sdhci_send_command(struct sdhci_host *host, struct mmc_command *cmd)
                 flags |= SDHCI_CMD_CRC;
         if (cmd->flags & MMC_RSP_OPCODE)
                 flags |= SDHCI_CMD_INDEX;
-        if (cmd->data)
+
+        /* CMD19 is special in that the Data Present Select should be set */
+        if (cmd->data || (cmd->opcode == MMC_SEND_TUNING_BLOCK))
                 flags |= SDHCI_CMD_DATA;
 
         sdhci_writew(host, SDHCI_MAKE_CMD(cmd->opcode, flags), SDHCI_COMMAND);
@@ -1501,12 +1505,157 @@ static int sdhci_start_signal_voltage_switch(struct mmc_host *mmc,
                 return 0;
 }
 
+static int sdhci_execute_tuning(struct mmc_host *mmc)
+{
+        struct sdhci_host *host;
+        u16 ctrl;
+        u32 ier;
+        int tuning_loop_counter = MAX_TUNING_LOOP;
+        unsigned long timeout;
+        int err = 0;
+
+        host = mmc_priv(mmc);
+
+        disable_irq(host->irq);
+        spin_lock(&host->lock);
+
+        ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+
+        /*
+         * Host Controller needs tuning only in case of SDR104 mode
+         * and for SDR50 mode when Use Tuning for SDR50 is set in
+         * Capabilities register.
+         */
+        if (((ctrl & SDHCI_CTRL_UHS_MASK) == SDHCI_CTRL_UHS_SDR104) ||
+            (((ctrl & SDHCI_CTRL_UHS_MASK) == SDHCI_CTRL_UHS_SDR50) &&
+            (host->flags & SDHCI_SDR50_NEEDS_TUNING)))
+                ctrl |= SDHCI_CTRL_EXEC_TUNING;
+        else {
+                spin_unlock(&host->lock);
+                enable_irq(host->irq);
+                return 0;
+        }
+
+        sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
+
+        /*
+         * As per the Host Controller spec v3.00, tuning command
+         * generates Buffer Read Ready interrupt, so enable that.
+         *
+         * Note: The spec clearly says that when tuning sequence
+         * is being performed, the controller does not generate
+         * interrupts other than Buffer Read Ready interrupt. But
+         * to make sure we don't hit a controller bug, we _only_
+         * enable Buffer Read Ready interrupt here.
+         */
+        ier = sdhci_readl(host, SDHCI_INT_ENABLE);
+        sdhci_clear_set_irqs(host, ier, SDHCI_INT_DATA_AVAIL);
+
+        /*
+         * Issue CMD19 repeatedly till Execute Tuning is set to 0 or the number
+         * of loops reaches 40 times or a timeout of 150ms occurs.
+         */
+        timeout = 150;
+        do {
+                struct mmc_command cmd = {0};
+                struct mmc_request mrq = {0};
+
+                if (!tuning_loop_counter && !timeout)
+                        break;
+
+                cmd.opcode = MMC_SEND_TUNING_BLOCK;
+                cmd.arg = 0;
+                cmd.flags = MMC_RSP_R1 | MMC_CMD_ADTC;
+                cmd.retries = 0;
+                cmd.data = NULL;
+                cmd.error = 0;
+
+                mrq.cmd = &cmd;
+                host->mrq = &mrq;
+
+                /*
+                 * In response to CMD19, the card sends 64 bytes of tuning
+                 * block to the Host Controller. So we set the block size
+                 * to 64 here.
+                 */
+                sdhci_writew(host, SDHCI_MAKE_BLKSZ(7, 64), SDHCI_BLOCK_SIZE);
+
+                /*
+                 * The tuning block is sent by the card to the host controller.
+                 * So we set the TRNS_READ bit in the Transfer Mode register.
+                 * This also takes care of setting DMA Enable and Multi Block
+                 * Select in the same register to 0.
+                 */
+                sdhci_writew(host, SDHCI_TRNS_READ, SDHCI_TRANSFER_MODE);
+
+                sdhci_send_command(host, &cmd);
+
+                host->cmd = NULL;
+                host->mrq = NULL;
+
+                spin_unlock(&host->lock);
+                enable_irq(host->irq);
+
+                /* Wait for Buffer Read Ready interrupt */
+                wait_event_interruptible_timeout(host->buf_ready_int,
+                                        (host->tuning_done == 1),
+                                        msecs_to_jiffies(50));
+                disable_irq(host->irq);
+                spin_lock(&host->lock);
+
+                if (!host->tuning_done) {
+                        printk(KERN_INFO DRIVER_NAME ": Timeout waiting for "
+                                "Buffer Read Ready interrupt during tuning "
+                                "procedure, falling back to fixed sampling "
+                                "clock\n");
+                        ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+                        ctrl &= ~SDHCI_CTRL_TUNED_CLK;
+                        ctrl &= ~SDHCI_CTRL_EXEC_TUNING;
+                        sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
+
+                        err = -EIO;
+                        goto out;
+                }
+
+                host->tuning_done = 0;
+
+                ctrl = sdhci_readw(host, SDHCI_HOST_CONTROL2);
+                tuning_loop_counter--;
+                timeout--;
+                mdelay(1);
+        } while (ctrl & SDHCI_CTRL_EXEC_TUNING);
+
+        /*
+         * The Host Driver has exhausted the maximum number of loops allowed,
+         * so use fixed sampling frequency.
+         */
+        if (!tuning_loop_counter || !timeout) {
+                ctrl &= ~SDHCI_CTRL_TUNED_CLK;
+                sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
+        } else {
+                if (!(ctrl & SDHCI_CTRL_TUNED_CLK)) {
+                        printk(KERN_INFO DRIVER_NAME ": Tuning procedure"
+                                " failed, falling back to fixed sampling"
+                                " clock\n");
+                        err = -EIO;
+                }
+        }
+
+out:
+        sdhci_clear_set_irqs(host, SDHCI_INT_DATA_AVAIL, ier);
+        spin_unlock(&host->lock);
+        enable_irq(host->irq);
+
+        return err;
+}
+
 static const struct mmc_host_ops sdhci_ops = {
         .request        = sdhci_request,
         .set_ios        = sdhci_set_ios,
         .get_ro         = sdhci_get_ro,
         .enable_sdio_irq = sdhci_enable_sdio_irq,
         .start_signal_voltage_switch    = sdhci_start_signal_voltage_switch,
+        .execute_tuning                 = sdhci_execute_tuning,
 };
 
 /*****************************************************************************\
@@ -1724,6 +1873,16 @@ static void sdhci_data_irq(struct sdhci_host *host, u32 intmask)
 {
         BUG_ON(intmask == 0);
 
+        /* CMD19 generates _only_ Buffer Read Ready interrupt */
+        if (intmask & SDHCI_INT_DATA_AVAIL) {
+                if (SDHCI_GET_CMD(sdhci_readw(host, SDHCI_COMMAND)) ==
+                    MMC_SEND_TUNING_BLOCK) {
+                        host->tuning_done = 1;
+                        wake_up(&host->buf_ready_int);
+                        return;
+                }
+        }
+
         if (!host->data) {
                 /*
                  * The "data complete" interrupt is also used to
@@ -2160,6 +2319,10 @@ int sdhci_add_host(struct sdhci_host *host)
         if (caps[1] & SDHCI_SUPPORT_DDR50)
                 mmc->caps |= MMC_CAP_UHS_DDR50;
 
+        /* Does the host needs tuning for SDR50? */
+        if (caps[1] & SDHCI_USE_SDR50_TUNING)
+                host->flags |= SDHCI_SDR50_NEEDS_TUNING;
+
         /* Driver Type(s) (A, C, D) supported by the host */
         if (caps[1] & SDHCI_DRIVER_TYPE_A)
                 mmc->caps |= MMC_CAP_DRIVER_TYPE_A;
@@ -2313,6 +2476,9 @@ int sdhci_add_host(struct sdhci_host *host)
 
         setup_timer(&host->timer, sdhci_timeout_timer, (unsigned long)host);
 
+        if (host->version >= SDHCI_SPEC_300)
+                init_waitqueue_head(&host->buf_ready_int);
+
         ret = request_irq(host->irq, sdhci_irq, IRQF_SHARED,
                 mmc_hostname(mmc), host);
         if (ret)