[U-Boot] [PATCH v2] mmc: Split device init to decouple OCR-polling delay
Simon Glass
sjg at chromium.org
Sat Dec 1 00:05:15 CET 2012
Hi,
On Thu, Nov 29, 2012 at 7:20 AM, Jae hoon Chung <jh80.chung at gmail.com> wrote:
> Hi Simon,
>
> Is it saved the 200ms? Could you tell me your environment?
> I will check this patch..and share the result.
The environment is snow (Samsung ARM Chromebook). The time save only
comes from not waiting for the MMC init. So:
1. Kick off MMC init
2. Go off and do something else for 200ms
3. Come back and MMC init should complete immediately
Regards,
Simon
>
> Best Regards,
> Jaehoon Chung
>
> 2012/11/29 Simon Glass <sjg at chromium.org>:
>> 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>
>> ---
>> Changes in v2:
>> - Rebase to master
>>
>> drivers/mmc/mmc.c | 137 ++++++++++++++++++++++++++++++++++++++++------------
>> include/mmc.h | 30 ++++++++++++
>> 2 files changed, 135 insertions(+), 32 deletions(-)
>>
>> diff --git a/drivers/mmc/mmc.c b/drivers/mmc/mmc.c
>> index 72e8ce6..09695e8 100644
>> --- a/drivers/mmc/mmc.c
>> +++ b/drivers/mmc/mmc.c
>> @@ -503,48 +503,70 @@ static int sd_send_op_cond(struct mmc *mmc)
>> return 0;
>> }
>>
>> -static int mmc_send_op_cond(struct mmc *mmc)
>> +/* 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 timeout = 10000;
>> - struct mmc_cmd cmd;
>> 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)
>> +{
>> + struct mmc_cmd cmd;
>> + 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;
>> @@ -1227,7 +1249,7 @@ 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;
>>
>> @@ -1267,17 +1289,48 @@ 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;
>> }
>>
>> @@ -1315,6 +1368,25 @@ 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);
>> @@ -1325,5 +1397,6 @@ 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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