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Date:	Mon, 21 May 2012 17:00:03 +0530
From:	Subhash Jadavani <subhashj@...eaurora.org>
To:	Seungwon Jeon <tgih.jun@...sung.com>
CC:	linux-mmc@...r.kernel.org, 'Chris Ball' <cjb@...top.org>,
	merez@...eaurora.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/3] mmc: core: Add packed command feature of eMMC4.5


Hi Seungwon,

Sorry for commenting on this late. I have one comment below. Please 
check if it makes sense or not.

On 5/17/2012 3:10 PM, Seungwon Jeon wrote:
> This patch adds packed command feature of eMMC4.5.
> The maximum number for packing read(or write) is offered
> and exception event relevant to packed command which is
> used for error handling is enabled. If host wants to use
> this feature, MMC_CAP2_PACKED_CMD should be set.
>
> Signed-off-by: Seungwon Jeon<tgih.jun@...sung.com>
> ---
>   drivers/mmc/core/mmc.c   |   24 ++++++++++++++++++++++++
>   include/linux/mmc/card.h |    3 +++
>   include/linux/mmc/host.h |    4 ++++
>   include/linux/mmc/mmc.h  |   15 +++++++++++++++
>   4 files changed, 46 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/mmc/core/mmc.c b/drivers/mmc/core/mmc.c
> index 2f0e11c..8310ce8 100644
> --- a/drivers/mmc/core/mmc.c
> +++ b/drivers/mmc/core/mmc.c
> @@ -516,6 +516,11 @@ static int mmc_read_ext_csd(struct mmc_card *card, u8 *ext_csd)
>   		} else {
>   			card->ext_csd.data_tag_unit_size = 0;
>   		}
> +
> +		card->ext_csd.max_packed_writes =
> +			ext_csd[EXT_CSD_MAX_PACKED_WRITES];
> +		card->ext_csd.max_packed_reads =
> +			ext_csd[EXT_CSD_MAX_PACKED_READS];
>   	}
>
>   out:
> @@ -1244,6 +1249,25 @@ static int mmc_init_card(struct mmc_host *host, u32 ocr,
>   		}
>   	}
>
> +	if ((host->caps2&  MMC_CAP2_PACKED_CMD)&&
> +			(card->ext_csd.max_packed_writes>  0)&&
> +			(card->ext_csd.max_packed_reads>  0)) {
why both max_packed_reads and max_packed_writes need to be non-zero to 
enable the write packing event? What if write packing is not supported 
by card and only read packing is supported? Shouldn't we still make the 
read packing work?

I would suggest to change it like this:
     if (  (host->caps2 & MMC_CAP2_PACKED_WR && 
card->ext_csd.max_packed_writes > 0) ||
            (host->caps2 & MMC_CAP2_PACKED_RD && 
card->ext_csd.max_packed_reads > 0)
> +		err = mmc_switch(card, EXT_CSD_CMD_SET_NORMAL,
> +				EXT_CSD_EXP_EVENTS_CTRL,
> +				EXT_CSD_PACKED_EVENT_EN,
> +				card->ext_csd.generic_cmd6_time);
> +		if (err&&  err != -EBADMSG)
> +			goto free_card;
> +		if (err) {
> +			pr_warning("%s: Enabling packed event failed\n",
> +					mmc_hostname(card->host));
> +			card->ext_csd.packed_event_en = 0;
> +			err = 0;
> +		} else {
> +			card->ext_csd.packed_event_en = 1;
> +		}
> +	}
> +
>   	if (!oldcard)
>   		host->card = card;
>
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index d76513b..4aeb4e9 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -53,6 +53,9 @@ struct mmc_ext_csd {
>   	u8			part_config;
>   	u8			cache_ctrl;
>   	u8			rst_n_function;
> +	u8			max_packed_writes;
> +	u8			max_packed_reads;
> +	u8			packed_event_en;
>   	unsigned int		part_time;		/* Units: ms */
>   	unsigned int		sa_timeout;		/* Units: 100ns */
>   	unsigned int		generic_cmd6_time;	/* Units: 10ms */
> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
> index 0707d22..9d0d946 100644
> --- a/include/linux/mmc/host.h
> +++ b/include/linux/mmc/host.h
> @@ -238,6 +238,10 @@ struct mmc_host {
>   #define MMC_CAP2_BROKEN_VOLTAGE	(1<<  7)	/* Use the broken voltage */
>   #define MMC_CAP2_DETECT_ON_ERR	(1<<  8)	/* On I/O err check card removal */
>   #define MMC_CAP2_HC_ERASE_SZ	(1<<  9)	/* High-capacity erase size */
> +#define MMC_CAP2_PACKED_RD	(1<<  10)	/* Allow packed read */
> +#define MMC_CAP2_PACKED_WR	(1<<  11)	/* Allow packed write */
> +#define MMC_CAP2_PACKED_CMD	(MMC_CAP2_PACKED_RD | \
> +				 MMC_CAP2_PACKED_WR) /* Allow packed commands */
>
>   	mmc_pm_flag_t		pm_caps;	/* supported pm features */
>   	unsigned int        power_notify_type;
> diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
> index d425cab..254901a 100644
> --- a/include/linux/mmc/mmc.h
> +++ b/include/linux/mmc/mmc.h
> @@ -139,6 +139,7 @@ static inline bool mmc_op_multi(u32 opcode)
>   #define R1_CURRENT_STATE(x)	((x&  0x00001E00)>>  9)	/* sx, b (4 bits) */
>   #define R1_READY_FOR_DATA	(1<<  8)	/* sx, a */
>   #define R1_SWITCH_ERROR		(1<<  7)	/* sx, c */
> +#define R1_EXP_EVENT		(1<<  6)	/* sr, a */
>   #define R1_APP_CMD		(1<<  5)	/* sr, c */
>
>   #define R1_STATE_IDLE	0
> @@ -274,6 +275,10 @@ struct _mmc_csd {
>   #define EXT_CSD_FLUSH_CACHE		32      /* W */
>   #define EXT_CSD_CACHE_CTRL		33      /* R/W */
>   #define EXT_CSD_POWER_OFF_NOTIFICATION	34	/* R/W */
> +#define EXT_CSD_PACKED_FAILURE_INDEX	35	/* RO */
> +#define EXT_CSD_PACKED_CMD_STATUS	36	/* RO */
> +#define EXT_CSD_EXP_EVENTS_STATUS	54	/* RO, 2 bytes */
> +#define EXT_CSD_EXP_EVENTS_CTRL	56	/* R/W, 2 bytes */
>   #define EXT_CSD_DATA_SECTOR_SIZE	61	/* R */
>   #define EXT_CSD_GP_SIZE_MULT		143	/* R/W */
>   #define EXT_CSD_PARTITION_ATTRIBUTE	156	/* R/W */
> @@ -318,6 +323,8 @@ struct _mmc_csd {
>   #define EXT_CSD_CACHE_SIZE		249	/* RO, 4 bytes */
>   #define EXT_CSD_TAG_UNIT_SIZE		498	/* RO */
>   #define EXT_CSD_DATA_TAG_SUPPORT	499	/* RO */
> +#define EXT_CSD_MAX_PACKED_WRITES	500	/* RO */
> +#define EXT_CSD_MAX_PACKED_READS	501	/* RO */
>   #define EXT_CSD_HPI_FEATURES		503	/* RO */
>
>   /*
> @@ -377,6 +384,14 @@ struct _mmc_csd {
>   #define EXT_CSD_PWR_CL_4BIT_MASK	0x0F	/* 8 bit PWR CLS */
>   #define EXT_CSD_PWR_CL_8BIT_SHIFT	4
>   #define EXT_CSD_PWR_CL_4BIT_SHIFT	0
> +
> +#define EXT_CSD_PACKED_EVENT_EN	(1<<  3)
> +
> +#define EXT_CSD_PACKED_FAILURE	(1<<  3)
> +
> +#define EXT_CSD_PACKED_GENERIC_ERROR	(1<<  0)
> +#define EXT_CSD_PACKED_INDEXED_ERROR	(1<<  1)
> +
>   /*
>    * MMC_SWITCH access modes
>    */

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