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

[Adrian Hunter <adrian.hunter@intel.com>]

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/commit/
>> 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.

> 
> 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.
>