RE: [PATCH] mmc: sd: Remove the patch that fix signal voltage when there is no power cycle

["Seunghui Lee" <sh043.lee@samsung.com>]

> -----Original Message-----
> From: Adrian Hunter <adrian.hunter@intel.com>
> Sent: Tuesday, July 26, 2022 7:57 PM
> To: Seunghui Lee <sh043.lee@samsung.com>; linux-mmc@vger.kernel.org;
> adrian.hunter@intel.com
> Cc: 'DooHyun Hwang' <dh0421.hwang@samsung.com>
> Subject: Re: [PATCH] mmc: sd: Remove the patch that fix signal voltage
> when there is no power cycle
> 
> On 26/07/22 05:56, Seunghui Lee wrote:
> >> -----Original Message-----
> >> From: Seunghui Lee <sh043.lee@samsung.com>
> >> Sent: Thursday, July 21, 2022 2:59 PM
> >> To: ulf.hansson@linaro.org; linux-mmc@vger.kernel.org;
> >> adrian.hunter@intel.com
> >> Cc: Seunghui Lee <sh043.lee@samsung.com>; DooHyun Hwang
> >> <dh0421.hwang@samsung.com>
> >> Subject: [PATCH] mmc: sd: Remove the patch that fix signal voltage
> >> when there is no power cycle
> >>
> >> At first, all error flow of mmc_set_uhs_voltage() has power cycle
> >> except R1_ERROR and no start_signal_voltage_switch() func pointer.
> >>
> >> There is the performance regression issue of SDR104 SD card from the
> >> market VOC. Normally, once a SDR104 SD card fails to switch voltage,
> >> it works HS mode.
> >> And then it initializes SDR104 mode after system resume or error
> handling.
> >>
> >> However, with below patch,
> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/co
> >> mmit/
> >> drivers/mmc/core/sd.c?id=6a11fc47f175c8d87018e89cb58e2d36c66534cb
> >> Once a SD card does, it initializes SDR25 mode forever after system
> >> resume or error handling(re-initialized).
> >> Host updates sd3_bus_mode by calling mmc_read_switch(), the value of
> >> sd3_bus_mode doesn't set for SDR104, SDR50 and DDR50 mode.
> >>
> >> So, if host doesn't update sd3_bus_mode, the SD card works SDR104
> >> mode after system resume or error-handling.
> >>
> >> Here is an example.
> >>
> >> AS-IS : test log
> >> // normal case : sd3_bus_mode = 0x1F, sd_bus_speed = SDR104, clock
> 208MHz
> >> [  111.907789] [1:    kworker/1:3:  772] [TEST] mmc_sd_init_card: 1119:
> >> caps=0x407f020f, sd3_bus_mode=0x1f, v18_fixup_failed false,
> >> signal_voltage =0x1.
> >> [  111.907824] [1:    kworker/1:3:  772] [TEST] mmc_sd_init_card: 1149:
> rocr
> >> 0xc1ff8000, S18A, uhs.
> >> [  111.908707] [1:    kworker/1:3:  772] [TEST] sd_update_bus_speed_mode:
> >> caps 0x407f020f, sd3_bus_mode = 0x1f, sd_bus_speed = 3, card->ocr =
> >> 0x40000.
> >> [  111.912484] [1:    kworker/1:3:  772] [TEST] sd_set_bus_speed_mode:
> >> sd_bus_speed=3, timing=6, uhs_max_dtr=208000000, card->ocr=0x40000.
> >> // resume : issue occurs : SDcard doesn't release busy for checking
> >> 10 times
> >> [  112.096550] [5:    kworker/5:2:  207] [TEST] mmc_sd_init_card: 1040:
> >> card->ocr 0x40000.
> >> [  112.096560] [5:    kworker/5:2:  207] [TEST] mmc_sd_get_cid: ocr
> >> 0x40000(pocr 0x40000), retries 10.
> >> ...
> >> [  114.531129] [5:    kworker/5:2:  207] [TEST] mmc_power_cycle.
> >> [  114.579500] [5:    kworker/5:2:  207] [TEST] mmc_sd_get_cid: ocr
> >> 0x41040000(pocr 0x40000), retries 0.
> >> [  114.579506] [5:    kworker/5:2:  207] mmc0: Skipping voltage switch
> >> [  114.757575] [5:    kworker/5:2:  207] [TEST] mmc_sd_init_card: 1119:
> >> caps=0x407f020f, sd3_bus_mode=0x1f, v18_fixup_failed false,
> >> signal_voltage =0x0.
> >> [  114.757583] [5:    kworker/5:2:  207] [TEST] mmc_sd_init_card: 1128:
> >> switch with oldcard.
> >> [  114.759742] [5:    kworker/5:2:  207] [TEST] mmc_read_switch:
> sd_switch
> >> ret 0, sd3_bus_mode=3.
> >> // sd3_bus_mode = 0x3 supports HS, SDR25 and SDR12
> >> [  114.759750] [5:    kworker/5:2:  207] [TEST] mmc_sd_init_card: 1157:
> >> switch hs.
> >> // next resume : the SDcard initializes to SDR25(HS)
> >> mode(sd_bus_speed = 1) by sd3_bus_mode setting with clk 50MHz
> >> [  114.968346] [5:    kworker/5:2:  207] [TEST] mmc_sd_init_card: 1040:
> >> card->ocr 0x40000.
> >> [  114.968359] [5:    kworker/5:2:  207] [TEST] mmc_sd_get_cid: ocr
> >> 0x40000(pocr 0x40000), retries 10.
> >> [  115.167346] [5:    kworker/5:2:  207] [TEST] mmc_sd_init_card: 1119:
> >> caps=0x407f020f, sd3_bus_mode=0x3, v18_fixup_failed false,
> >> signal_voltage =0x1.
> >> [  115.167366] [5:    kworker/5:2:  207] [TEST] mmc_sd_init_card: 1149:
> rocr
> >> 0xc1ff8000, S18A, uhs.
> >> [  115.168041] [5:    kworker/5:2:  207] [TEST] mmc_sd_init_uhs_card:
> before
> >> update: caps 0x407f020f, sd3_bus_mode = 3, sd_bus_speed = 3,
> >> card->ocr = 0x40000.
> >> [  115.168051] [5:    kworker/5:2:  207] [TEST] sd_update_bus_speed_mode:
> >> caps 0x407f020f, sd3_bus_mode = 3, sd_bus_speed = 1, card->ocr =
> 0x40000.
> >> [  115.169176] [5:    kworker/5:2:  207] [TEST] sd_set_bus_speed_mode:
> >> sd_bus_speed=1, timing=4, uhs_max_dtr=50000000, card->ocr=0x40000.
> >>
> >> TO-BE : TEST log with this commit
> >> // resume : issue occurs : SDcard doesn't release busy for checking
> >> 10 times
> >> [ 1843.594805] [4:    kworker/4:5:21512] [TEST] mmc_sd_get_cid: ocr
> >> 0x41040000(pocr 0x40000), retries 0.
> >> [ 1843.594812] [4:    kworker/4:5:21512] mmc0: Skipping voltage switch
> >> [ 1843.772555] [4:    kworker/4:5:21512] [TEST] mmc_sd_init_card: 1122:
> >> caps=0x407f020f, sd3_bus_mode=0x1f, v18_fixup_failed false,
> >> signal_voltage =0x0.
> >> // no update sd3_bus_mode value
> >> [ 1843.772563] [4:    kworker/4:5:21512] [TEST] mmc_sd_init_card: 1164:
> >> switch hs.
> >> // next resume : the SDcard initializes to SDR104
> >> [ 1844.191295] [5:   kworker/5:93: 2282] [TEST] mmc_sd_init_card: 1122:
> >> caps=0x407f020f, sd3_bus_mode=0x1f, v18_fixup_failed false,
> >> signal_voltage =0x1.
> >> [ 1844.191315] [5:   kworker/5:93: 2282] [TEST] mmc_sd_init_card: 1154:
> >> rocr 0xc1ff8000, S18A, uhs.
> >> [ 1844.192175] [5:   kworker/5:93: 2282] [TEST] mmc_sd_init_uhs_card:
> >> before update: caps 0x407f020f, sd3_bus_mode = 0x1f, sd_bus_speed =
> >> 3,
> >> card->ocr = 0x40000.
> >> [ 1844.192187] [5:   kworker/5:93: 2282] [TEST]
> sd_update_bus_speed_mode:
> >> caps 0x407f020f, sd3_bus_mode = 0x1f, sd_bus_speed = 3, card->ocr =
> >> 0x40000.
> >> [ 1844.198697] [5:   kworker/5:93: 2282] [TEST] sd_set_bus_speed_mode:
> >> sd_bus_speed=3, timing=6, uhs_max_dtr=208000000, card->ocr=0x40000.
> >>
> >> Signed-off-by: Seunghui Lee <sh043.lee@samsung.com>
> >> Tested-by: DooHyun Hwang <dh0421.hwang@samsung.com>
> >> ---
> >>  drivers/mmc/core/sd.c | 47
> >> ++-----------------------------------------
> >>  1 file changed, 2 insertions(+), 45 deletions(-)
> >>
> >> diff --git a/drivers/mmc/core/sd.c b/drivers/mmc/core/sd.c index
> >> cee4c0b59f43..4e3d39956185 100644
> >> --- a/drivers/mmc/core/sd.c
> >> +++ b/drivers/mmc/core/sd.c
> >> @@ -1001,18 +1001,6 @@ unsigned mmc_sd_get_max_clock(struct mmc_card
> *card)
> >>  	return max_dtr;
> >>  }
> >>
> >> -static bool mmc_sd_card_using_v18(struct mmc_card *card) -{
> >> -	/*
> >> -	 * According to the SD spec., the Bus Speed Mode (function group 1)
> >> bits
> >> -	 * 2 to 4 are zero if the card is initialized at 3.3V signal level.
> >> Thus
> >> -	 * they can be used to determine if the card has already switched
> >> to
> >> -	 * 1.8V signaling.
> >> -	 */
> >> -	return card->sw_caps.sd3_bus_mode &
> >> -	       (SD_MODE_UHS_SDR50 | SD_MODE_UHS_SDR104 | SD_MODE_UHS_DDR50);
> >> -}
> >> -
> >>  static int sd_write_ext_reg(struct mmc_card *card, u8 fno, u8 page,
> >> u16 offset,
> >>  			    u8 reg_data)
> >>  {
> >> @@ -1400,10 +1388,9 @@ static int mmc_sd_init_card(struct mmc_host
> >> *host,
> >> u32 ocr,
> >>  	int err;
> >>  	u32 cid[4];
> >>  	u32 rocr = 0;
> >> -	bool v18_fixup_failed = false;
> >>
> >>  	WARN_ON(!host->claimed);
> >> -retry:
> >> +
> >>  	err = mmc_sd_get_cid(host, ocr, cid, &rocr);
> >>  	if (err)
> >>  		return err;
> >> @@ -1472,36 +1459,6 @@ static int mmc_sd_init_card(struct mmc_host
> >> *host,
> >> u32 ocr,
> >>  	if (err)
> >>  		goto free_card;
> >>
> >> -	/*
> >> -	 * If the card has not been power cycled, it may still be using
> >> 1.8V
> >> -	 * signaling. Detect that situation and try to initialize a UHS-I
> >> (1.8V)
> >> -	 * transfer mode.
> >> -	 */
> >> -	if (!v18_fixup_failed && !mmc_host_is_spi(host) &&
> >> mmc_host_uhs(host) &&
> >> -	    mmc_sd_card_using_v18(card) &&
> >> -	    host->ios.signal_voltage != MMC_SIGNAL_VOLTAGE_180) {
> >> -		/*
> >> -		 * Re-read switch information in case it has changed since
> >> -		 * oldcard was initialized.
> >> -		 */
> >> -		if (oldcard) {
> >> -			err = mmc_read_switch(card);
> >> -			if (err)
> >> -				goto free_card;
> >> -		}
> >> -		if (mmc_sd_card_using_v18(card)) {
> >> -			if (mmc_host_set_uhs_voltage(host) ||
> >> -			    mmc_sd_init_uhs_card(card)) {
> >> -				v18_fixup_failed = true;
> >> -				mmc_power_cycle(host, ocr);
> >> -				if (!oldcard)
> >> -					mmc_remove_card(card);
> >> -				goto retry;
> >> -			}
> >> -			goto done;
> >> -		}
> >> -	}
> >> -
> >>  	/* Initialization sequence for UHS-I cards */
> >>  	if (rocr & SD_ROCR_S18A && mmc_host_uhs(host)) {
> >>  		err = mmc_sd_init_uhs_card(card);
> >> @@ -1566,7 +1523,7 @@ static int mmc_sd_init_card(struct mmc_host
> >> *host,
> >> u32 ocr,
> >>  		err = -EINVAL;
> >>  		goto free_card;
> >>  	}
> >> -done:
> >> +
> >>  	host->card = card;
> >>  	return 0;
> >>
> >> --
> >> 2.29.0
> >
> > Dear All,
> >
> > Please review this commit.
> 
> I have started to look at it, but my time is limited at the moment.
> 
> Note the original patch is 5 years old and fixes a real problem, so we
> don't want to just throw it away.
> 

Dear Mr. hunter,

Could you check this with below patch?

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/mmc/core/core.c?id=147186f531ae49c18b7a9091a2c40e83b3d95649

In the mmc_set_uhs_voltaga func(),
once it occurs error, it has power_cycle except R1_ERROR with CMD11.
So, When mmc_set_uhs_voltage() return error,
host and card can't leave 1.8V voltage.

Regards,

> >
> > Once the SDR104 SD card fails to switch voltage, there is no chance to
> > work SDR104 bus speed again due to update sd3_bus_mode.
> >
> > To fix this regression issue, do not update sd3_bus_mode.
> > And then it has the chance to work SDR104 again.
> >
> > AS-IS:
> > voltage_switch fail -> mmc_read_switch() -> HS mode next system resume
> > voltage switch success -> SDR25 mode
> >
> > TO-BE:
> > Voltage switch fail -> HS mode
> > Next system resume
> > Voltage switch success -> SDR104 mode
> >
> > And plus, mmc_set_uhs_voltage() has power_cycle now.
> > It means that if voltage switch fails, the card initializes 3.3V
> > signal level.
> >
> > Regards,
> > Seunghui Lee.
> >