Re: [PATCH 09/11] mmc: core: Read the SD function extension registers for power management

[Shawn Lin <shawn.lin@rock-chips.com>]

On 2021/5/5 0:12, Ulf Hansson wrote:
> In SD spec v4.x the SD function extension registers were introduced. A

I have a v4.0 spec and it doesn't state that v4.0 suppports reading
extension registers but just says TBD instead.  So I guess v4.x doesn't
include v4.0 ?

> specific function register were added to let the card announce support for
> optional features in regards to power management. The features that were
> added are "Power Off Notification", "Power Down Mode" and "Power
> Sustenance".
> 
> As a first step, let's read and parse this register for power management
> during the SD card initialization and store the information about the
> supported features in the struct mmc_card. In this way, we prepare for
> subsequent changes to implement the complete support for the new features.
> 
> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> ---
>   drivers/mmc/core/sd.c    | 178 +++++++++++++++++++++++++++++++++++++++
>   include/linux/mmc/card.h |  13 +++
>   include/linux/mmc/sd.h   |   3 +
>   3 files changed, 194 insertions(+)
> 
> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c
> index de7b5f8df550..cb5e8b2fc32f 100644
> --- a/drivers/mmc/core/sd.c
> +++ b/drivers/mmc/core/sd.c
> @@ -996,6 +996,177 @@ static bool mmc_sd_card_using_v18(struct mmc_card *card)
>   	       (SD_MODE_UHS_SDR50 | SD_MODE_UHS_SDR104 | SD_MODE_UHS_DDR50);
>   }
>   
> +static int sd_read_ext_reg(struct mmc_card *card, u8 fno, u8 page,
> +			   u16 offset, u16 len, u8 *reg_buf)
> +{
> +	u32 cmd_args;
> +
> +	/*
> +	 * Command arguments of CMD48:
> +	 * [31:31] MIO (0 = memory).
> +	 * [30:27] FNO (function number).
> +	 * [26:26] reserved (0).
> +	 * [25:18] page number.
> +	 * [17:9] offset address.
> +	 * [8:0] length (0 = 1 byte, 1ff = 512 bytes).
> +	 */
> +	cmd_args = fno << 27 | page << 18 | offset << 9 | (len -1);
> +
> +	return mmc_send_adtc_data(card, card->host, SD_READ_EXTR_SINGLE,
> +				  cmd_args, reg_buf, 512);
> +}
> +
> +static int sd_parse_ext_reg_power(struct mmc_card *card, u8 fno, u8 page,
> +				  u16 offset)
> +{
> +	int err;
> +	u8 *reg_buf;
> +
> +	reg_buf = kzalloc(512, GFP_KERNEL);
> +	if (!reg_buf)
> +		return -ENOMEM;
> +
> +	/* Read the extension register for power management function. */
> +	err = sd_read_ext_reg(card, fno, page, offset, 512, reg_buf);
> +	if (err) {
> +		pr_warn("%s: error %d reading PM func of ext reg\n",
> +			mmc_hostname(card->host), err);
> +		goto out;
> +	}
> +
> +	/* PM revision consists of 4 bits. */
> +	card->ext_power.rev = reg_buf[0] & 0xf;
> +
> +	/* Power Off Notification support at bit 4. */
> +	if (reg_buf[1] & 0x10)
> +		card->ext_power.feature_support |= SD_EXT_POWER_OFF_NOTIFY;
> +
> +	/* Power Sustenance support at bit 5. */
> +	if (reg_buf[1] & 0x20)
> +		card->ext_power.feature_support |= SD_EXT_POWER_SUSTENANCE;
> +
> +	/* Power Down Mode support at bit 6. */
> +	if (reg_buf[1] & 0x40)
> +		card->ext_power.feature_support |= SD_EXT_POWER_DOWN_MODE;
> +
> +	card->ext_power.fno = fno;
> +	card->ext_power.page = page;
> +	card->ext_power.offset = offset;
> +
> +out:
> +	kfree(reg_buf);
> +	return err;
> +}
> +
> +static int sd_parse_ext_reg(struct mmc_card *card, u8 *gen_info_buf,
> +			    u16 *next_ext_addr)
> +{
> +	u8 num_regs, fno, page;
> +	u16 sfc, offset, ext = *next_ext_addr;
> +	u32 reg_addr;
> +
> +	/*
> +	 * Parse only one register set per extension, as that is sufficient to
> +	 * support the standard functions. This means another 48 bytes in the
> +	 * buffer must be available.
> +	 */
> +	if (ext + 48 > 512)
> +		return -EFAULT;
> +
> +	/* Standard Function Code */
> +	memcpy(&sfc, &gen_info_buf[ext], 2);
> +
> +	/* Address to the next extension. */
> +	memcpy(next_ext_addr, &gen_info_buf[ext + 40], 2);
> +
> +	/* Number of registers for this extension. */
> +	num_regs = gen_info_buf[ext + 42];
> +
> +	/* We support only one register per extension. */
> +	if (num_regs != 1)
> +		return 0;
> +
> +	/* Extension register address. */
> +	memcpy(&reg_addr, &gen_info_buf[ext + 44], 4);
> +
> +	/* 9 bits (0 to 8) contains the offset address. */
> +	offset = reg_addr & 0x1ff;
> +
> +	/* 8 bits (9 to 16) contains the page number. */
> +	page = reg_addr >> 9 & 0xff ;
> +
> +	/* 4 bits (18 to 21) contains the function number. */
> +	fno = reg_addr >> 18 & 0xf;
> +
> +	/* Standard Function Code for power management. */
> +	if (sfc == 0x1)
> +		return sd_parse_ext_reg_power(card, fno, page, offset);
> +
> +	return 0;
> +}
> +
> +static int sd_read_ext_regs(struct mmc_card *card)
> +{
> +	int err, i;
> +	u8 num_ext, *gen_info_buf;
> +	u16 rev, len, next_ext_addr;
> +
> +	if (mmc_host_is_spi(card->host))
> +		return 0;
> +
> +	if (!(card->scr.cmds & SD_SCR_CMD48_SUPPORT))
> +		return 0;
> +
> +	gen_info_buf = kzalloc(512, GFP_KERNEL);
> +	if (!gen_info_buf)
> +		return -ENOMEM;
> +
> +	/*
> +	 * Read 512 bytes of general info, which is found at function number 0,
> +	 * at page 0 and with no offset.
> +	 */
> +	err = sd_read_ext_reg(card, 0, 0, 0, 512, gen_info_buf);
> +	if (err) {
> +		pr_warn("%s: error %d reading general info of SD ext reg\n",
> +			mmc_hostname(card->host), err);
> +		goto out;
> +	}
> +
> +	/* General info structure revision. */
> +	memcpy(&rev, &gen_info_buf[0], 2);
> +
> +	/* Length of general info in bytes. */
> +	memcpy(&len, &gen_info_buf[2], 2);
> +
> +	/* Number of extensions to be find. */
> +	num_ext = gen_info_buf[4];
> +
> +	/* We support revision 0, but limit it to 512 bytes for simplicity. */
> +	if (rev != 0 || len > 512) {
> +		pr_warn("%s: non-supported SD ext reg layout\n",
> +			mmc_hostname(card->host));
> +		goto out;
> +	}
> +
> +	/*
> +	 * Parse the extension registers. The first extension should start
> +	 * immediately after the general info header (16 bytes).
> +	 */
> +	next_ext_addr = 16;
> +	for (i = 0; i < num_ext; i++) {
> +		err = sd_parse_ext_reg(card, gen_info_buf, &next_ext_addr);
> +		if (err) {
> +			pr_warn("%s: error %d parsing SD ext reg\n",
> +				mmc_hostname(card->host), err);
> +			goto out;
> +		}
> +	}
> +
> +out:
> +	kfree(gen_info_buf);
> +	return err;
> +}
> +
>   /*
>    * Handle the detection and initialisation of a card.
>    *
> @@ -1144,6 +1315,13 @@ static int mmc_sd_init_card(struct mmc_host *host, u32 ocr,
>   		}
>   	}
>   
> +	if (!oldcard) {
> +		/* Read/parse the extension registers. */
> +		err = sd_read_ext_regs(card);
> +		if (err)
> +			goto free_card;
> +	}
> +
>   	if (host->cqe_ops && !host->cqe_enabled) {
>   		err = host->cqe_ops->cqe_enable(host, card);
>   		if (!err) {
> diff --git a/include/linux/mmc/card.h b/include/linux/mmc/card.h
> index 858fc4d11240..03a862e93594 100644
> --- a/include/linux/mmc/card.h
> +++ b/include/linux/mmc/card.h
> @@ -191,6 +191,18 @@ struct sd_switch_caps {
>   #define SD_MAX_CURRENT_800	(1 << SD_SET_CURRENT_LIMIT_800)
>   };
>   
> +struct sd_ext_reg {
> +	u8			fno;
> +	u8			page;
> +	u16			offset;
> +	u8			rev;
> +	u8			feature_support;
> +/* Power Management Function. */
> +#define SD_EXT_POWER_OFF_NOTIFY	(1<<0)
> +#define SD_EXT_POWER_SUSTENANCE	(1<<1)
> +#define SD_EXT_POWER_DOWN_MODE	(1<<2)
> +};
> +
>   struct sdio_cccr {
>   	unsigned int		sdio_vsn;
>   	unsigned int		sd_vsn;
> @@ -292,6 +304,7 @@ struct mmc_card {
>   	struct sd_scr		scr;		/* extra SD information */
>   	struct sd_ssr		ssr;		/* yet more SD information */
>   	struct sd_switch_caps	sw_caps;	/* switch (CMD6) caps */
> +	struct sd_ext_reg	ext_power;	/* SD extension reg for PM */
>   
>   	unsigned int		sdio_funcs;	/* number of SDIO functions */
>   	atomic_t		sdio_funcs_probed; /* number of probed SDIO funcs */
> diff --git a/include/linux/mmc/sd.h b/include/linux/mmc/sd.h
> index 2236aa540faa..43bfc5c39ad4 100644
> --- a/include/linux/mmc/sd.h
> +++ b/include/linux/mmc/sd.h
> @@ -29,6 +29,9 @@
>   #define SD_APP_OP_COND           41   /* bcr  [31:0] OCR         R3  */
>   #define SD_APP_SEND_SCR          51   /* adtc                    R1  */
>   
> +  /* class 11 */
> +#define SD_READ_EXTR_SINGLE      48   /* adtc [31:0]             R1  */
> +
>   /* OCR bit definitions */
>   #define SD_OCR_S18R		(1 << 24)    /* 1.8V switching request */
>   #define SD_ROCR_S18A		SD_OCR_S18R  /* 1.8V switching accepted by card */
>