RE: [PATCH v6 1/3] mmc: core: Add packed command feature of eMMC4.5

[Seungwon Jeon]

Subhash Jadavani <subhashj@xxxxxxxxxxxxxx> wrote:
> 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@xxxxxxxxxxx>
> > ---
> >   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 have not experienced that case. But it seems like possible actually.
Spec doesn't mention two should be satisfied for packed command.
I'll apply your comment.

Best regards,
Seungwon Jeon
> 
> 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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