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

From: Ulf Hansson
Date: Fri May 07 2021 - 03:28:10 EST

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On Fri, 7 May 2021 at 04:06, Shawn Lin <shawn.lin@xxxxxxxxxxxxxx> wrote:
>
>
> 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 ?

Good question. The v4.0 spec introduces the CMD48/49 and CMD58/59,
while in v4.10 the spec adds the power management extensions.

I can update the commit message to better reflect this, if you prefer!?

Thanks a lot for reviewing!

Kind regards
Uffe

>
> > 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@xxxxxxxxxx>
> > ---
> > 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 */
> >
>
>

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In reply to: Shawn Lin: "Re: [PATCH 09/11] mmc: core: Read the SD function extension registers for power management"
Next in thread: Shawn Lin: "Re: [PATCH 09/11] mmc: core: Read the SD function extension registers for power management"
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