[U-Boot] [PATCH v2] mmc: Split device init to decouple OCR-polling delay

[Jaehoon Chung]

Hi,

This concept is very good.
But I have one question. I think need to call mmc_init() one more, right?
how did you save the boot time(200ms)?

On 11/29/2012 10:21 AM, Simon Glass wrote:
> 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.
snip..
> +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);
It need not to return? if err is IN_PROGRESS, next condition is immediately run.
Then i think we didn't save the time before adjust this patch.
> +
> +	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);
>