[U-Boot] [PATCH 2/2] mmc: Split device init to decouple OCR-polling delay
Simon Glass
sjg at chromium.org
Sun Oct 21 05:16:00 CEST 2012
From: Che-Liang Chiou <clchiou at chromium.org>
Most of time that MMC driver spends on initializing a device is polling
OCR (operation conditions register). To decouple this polling loop,
device init is split into two parts: The first part fires the OCR query
command, and the second part polls the result. So the caller is now no
longer bound to the OCR-polling delay; he may fire the query, go
somewhere and then come back later for the result.
To use this, call mmc_set_preinit() on any device which needs this.
This can save significant amounts of time on boot (e.g. 200ms) by
hiding the MMC init time behind other init.
Signed-off-by: Che-Liang Chiou <clchiou at chromium.org>
Signed-off-by: Simon Glass <sjg at chromium.org>
---
drivers/mmc/mmc.c | 135 ++++++++++++++++++++++++++++++++++++++++------------
include/mmc.h | 30 ++++++++++++
2 files changed, 134 insertions(+), 31 deletions(-)
diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
index 18a037d..d397326 100644
--- a/drivers/mmc/mmc.c
+++ b/drivers/mmc/mmc.c
@@ -594,48 +594,70 @@ sd_send_op_cond(struct mmc *mmc)
return 0;
}
+/* We pass in the cmd since otherwise the init seems to fail */
+static int mmc_send_op_cond_iter(struct mmc *mmc, struct mmc_cmd *cmd,
+ int use_arg)
+{
+ int err;
+
+ cmd->cmdidx = MMC_CMD_SEND_OP_COND;
+ cmd->resp_type = MMC_RSP_R3;
+ cmd->cmdarg = 0;
+ if (use_arg && !mmc_host_is_spi(mmc)) {
+ cmd->cmdarg =
+ (mmc->voltages &
+ (mmc->op_cond_response & OCR_VOLTAGE_MASK)) |
+ (mmc->op_cond_response & OCR_ACCESS_MODE);
+
+ if (mmc->host_caps & MMC_MODE_HC)
+ cmd->cmdarg |= OCR_HCS;
+ }
+ err = mmc_send_cmd(mmc, cmd, NULL);
+ if (err)
+ return err;
+ mmc->op_cond_response = cmd->response[0];
+ return 0;
+}
+
int mmc_send_op_cond(struct mmc *mmc)
{
- int timeout = 10000;
struct mmc_cmd cmd;
- int err;
+ int err, i;
/* Some cards seem to need this */
mmc_go_idle(mmc);
/* Asking to the card its capabilities */
- cmd.cmdidx = MMC_CMD_SEND_OP_COND;
- cmd.resp_type = MMC_RSP_R3;
- cmd.cmdarg = 0;
-
- err = mmc_send_cmd(mmc, &cmd, NULL);
+ mmc->op_cond_pending = 1;
+ for (i = 0; i < 2; i++) {
+ err = mmc_send_op_cond_iter(mmc, &cmd, i != 0);
+ if (err)
+ return err;
- if (err)
- return err;
+ /* exit if not busy (flag seems to be inverted) */
+ if (mmc->op_cond_response & OCR_BUSY)
+ return 0;
+ }
+ return IN_PROGRESS;
+}
- udelay(1000);
+int mmc_complete_op_cond(struct mmc *mmc)
+{
+ struct mmc_cmd cmd;
+ int timeout = 1000;
+ uint start;
+ int err;
+ mmc->op_cond_pending = 0;
+ start = get_timer(0);
do {
- cmd.cmdidx = MMC_CMD_SEND_OP_COND;
- cmd.resp_type = MMC_RSP_R3;
- cmd.cmdarg = (mmc_host_is_spi(mmc) ? 0 :
- (mmc->voltages &
- (cmd.response[0] & OCR_VOLTAGE_MASK)) |
- (cmd.response[0] & OCR_ACCESS_MODE));
-
- if (mmc->host_caps & MMC_MODE_HC)
- cmd.cmdarg |= OCR_HCS;
-
- err = mmc_send_cmd(mmc, &cmd, NULL);
-
+ err = mmc_send_op_cond_iter(mmc, &cmd, 1);
if (err)
return err;
-
- udelay(1000);
- } while (!(cmd.response[0] & OCR_BUSY) && timeout--);
-
- if (timeout <= 0)
- return UNUSABLE_ERR;
+ if (get_timer(start) > timeout)
+ return UNUSABLE_ERR;
+ udelay(100);
+ } while (!(mmc->op_cond_response & OCR_BUSY));
if (mmc_host_is_spi(mmc)) { /* read OCR for spi */
cmd.cmdidx = MMC_CMD_SPI_READ_OCR;
@@ -1295,7 +1317,7 @@ block_dev_desc_t *mmc_get_dev(int dev)
}
#endif
-int mmc_init(struct mmc *mmc)
+int mmc_start_init(struct mmc *mmc)
{
int err;
@@ -1335,17 +1357,48 @@ int mmc_init(struct mmc *mmc)
if (err == TIMEOUT) {
err = mmc_send_op_cond(mmc);
- if (err) {
+ if (err && err != IN_PROGRESS) {
printf("Card did not respond to voltage select!\n");
return UNUSABLE_ERR;
}
}
- err = mmc_startup(mmc);
+ if (err == IN_PROGRESS)
+ mmc->init_in_progress = 1;
+
+ return err;
+}
+
+static int mmc_complete_init(struct mmc *mmc)
+{
+ int err = 0;
+
+ if (mmc->op_cond_pending)
+ err = mmc_complete_op_cond(mmc);
+
+ if (!err)
+ err = mmc_startup(mmc);
if (err)
mmc->has_init = 0;
else
mmc->has_init = 1;
+ mmc->init_in_progress = 0;
+ return err;
+}
+
+int mmc_init(struct mmc *mmc)
+{
+ int err = IN_PROGRESS;
+ unsigned start = get_timer(0);
+
+ if (mmc->has_init)
+ return 0;
+ if (!mmc->init_in_progress)
+ err = mmc_start_init(mmc);
+
+ if (!err || err == IN_PROGRESS)
+ err = mmc_complete_init(mmc);
+ debug("%s: %d, time %lu\n", __func__, err, get_timer(start));
return err;
}
@@ -1383,6 +1436,25 @@ int get_mmc_num(void)
return cur_dev_num;
}
+void mmc_set_preinit(struct mmc *mmc, int preinit)
+{
+ mmc->preinit = preinit;
+}
+
+static void do_preinit(void)
+{
+ struct mmc *m;
+ struct list_head *entry;
+
+ list_for_each(entry, &mmc_devices) {
+ m = list_entry(entry, struct mmc, link);
+
+ if (m->preinit)
+ mmc_start_init(m);
+ }
+}
+
+
int mmc_initialize(bd_t *bis)
{
INIT_LIST_HEAD (&mmc_devices);
@@ -1393,5 +1465,6 @@ int mmc_initialize(bd_t *bis)
print_mmc_devices(',');
+ do_preinit();
return 0;
}
diff --git a/include/mmc.h b/include/mmc.h
index a13e2bd..445d714 100644
--- a/include/mmc.h
+++ b/include/mmc.h
@@ -62,6 +62,7 @@
#define UNUSABLE_ERR -17 /* Unusable Card */
#define COMM_ERR -18 /* Communications Error */
#define TIMEOUT -19
+#define IN_PROGRESS -20 /* operation is in progress */
#define MMC_CMD_GO_IDLE_STATE 0
#define MMC_CMD_SEND_OP_COND 1
@@ -260,6 +261,10 @@ struct mmc {
int (*init)(struct mmc *mmc);
int (*getcd)(struct mmc *mmc);
uint b_max;
+ char op_cond_pending; /* 1 if we are waiting on an op_cond command */
+ char init_in_progress; /* 1 if we have done mmc_start_init() */
+ char preinit; /* start init as early as possible */
+ uint op_cond_response; /* the response byte from the last op_cond */
};
int mmc_register(struct mmc *mmc);
@@ -276,6 +281,31 @@ int mmc_switch_part(int dev_num, unsigned int part_num);
int mmc_getcd(struct mmc *mmc);
void spl_mmc_load(void) __noreturn;
+/**
+ * Start device initialization and return immediately; it does not block on
+ * polling OCR (operation condition register) status. Then you should call
+ * mmc_init, which would block on polling OCR status and complete the device
+ * initializatin.
+ *
+ * @param mmc Pointer to a MMC device struct
+ * @return 0 on success, IN_PROGRESS on waiting for OCR status, <0 on error.
+ */
+int mmc_start_init(struct mmc *mmc);
+
+/**
+ * Set preinit flag of mmc device.
+ *
+ * This will cause the device to be pre-inited during mmc_initialize(),
+ * which may save boot time if the device is not accessed until later.
+ * Some eMMC devices take 200-300ms to init, but unfortunately they
+ * must be sent a series of commands to even get them to start preparing
+ * for operation.
+ *
+ * @param mmc Pointer to a MMC device struct
+ * @param preinit preinit flag value
+ */
+void mmc_set_preinit(struct mmc *mmc, int preinit);
+
#ifdef CONFIG_GENERIC_MMC
#define mmc_host_is_spi(mmc) ((mmc)->host_caps & MMC_MODE_SPI)
struct mmc *mmc_spi_init(uint bus, uint cs, uint speed, uint mode);
--
1.7.7.3
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