Re: [PATCH 2/2] phy: qualcomm: phy-qcom-eusb2-repeater: Don't zero-out registers

["Luca Weiss" <luca.weiss@fairphone.com>]

On Mon Jun 16, 2025 at 1:40 PM CEST, Dmitry Baryshkov wrote:
> On Mon, Jun 16, 2025 at 11:45:12AM +0200, Luca Weiss wrote:
>> Zeroing out registers does not happen in the downstream kernel, and will
>> "tune" the repeater in surely unexpected ways since most registers don't
>> have a reset value of 0x0.
>> 
>> Stop doing that and instead just set the registers that are in the init
>> sequence (though long term I don't think there's actually PMIC-specific
>> init sequences, there's board specific tuning, but that's a story for
>> another day).
>> 
>> Fixes: 99a517a582fc ("phy: qualcomm: phy-qcom-eusb2-repeater: Zero out untouched tuning regs")
>> Signed-off-by: Luca Weiss <luca.weiss@fairphone.com>
>> ---
>>  drivers/phy/qualcomm/phy-qcom-eusb2-repeater.c | 63 +++++++++++++-------------
>>  1 file changed, 32 insertions(+), 31 deletions(-)
>> 
>> diff --git a/drivers/phy/qualcomm/phy-qcom-eusb2-repeater.c b/drivers/phy/qualcomm/phy-qcom-eusb2-repeater.c
>> index 6bd1b3c75c779d2db2744703262e132cc439f76e..a246c897fedb2edfd376ac5fdc0423607f8c562b 100644
>> --- a/drivers/phy/qualcomm/phy-qcom-eusb2-repeater.c
>> +++ b/drivers/phy/qualcomm/phy-qcom-eusb2-repeater.c
>> @@ -61,8 +61,13 @@ enum eusb2_reg_layout {
>>  	LAYOUT_SIZE,
>>  };
>>  
>> +struct eusb2_repeater_init_tbl_reg {
>> +	u8 reg;
>> +	u8 value;
>> +};
>> +
>>  struct eusb2_repeater_cfg {
>> -	const u32 *init_tbl;
>> +	const struct eusb2_repeater_init_tbl_reg *init_tbl;
>>  	int init_tbl_num;
>>  	const char * const *vreg_list;
>>  	int num_vregs;
>> @@ -82,16 +87,16 @@ static const char * const pm8550b_vreg_l[] = {
>>  	"vdd18", "vdd3",
>>  };
>>  
>> -static const u32 pm8550b_init_tbl[NUM_TUNE_FIELDS] = {
>> -	[TUNE_IUSB2] = 0x8,
>> -	[TUNE_SQUELCH_U] = 0x3,
>> -	[TUNE_USB2_PREEM] = 0x5,
>> +static const struct eusb2_repeater_init_tbl_reg pm8550b_init_tbl[] = {
>> +	{ TUNE_IUSB2, 0x8 },
>> +	{ TUNE_SQUELCH_U, 0x3 },
>> +	{ TUNE_USB2_PREEM, 0x5 },
>>  };
>>  
>> -static const u32 smb2360_init_tbl[NUM_TUNE_FIELDS] = {
>> -	[TUNE_IUSB2] = 0x5,
>> -	[TUNE_SQUELCH_U] = 0x3,
>> -	[TUNE_USB2_PREEM] = 0x2,
>> +static const struct eusb2_repeater_init_tbl_reg smb2360_init_tbl[] = {
>> +	{ TUNE_IUSB2, 0x5 },
>> +	{ TUNE_SQUELCH_U, 0x3 },
>> +	{ TUNE_USB2_PREEM, 0x2 },
>>  };
>>  
>>  static const struct eusb2_repeater_cfg pm8550b_eusb2_cfg = {
>> @@ -129,17 +134,10 @@ static int eusb2_repeater_init(struct phy *phy)
>>  	struct eusb2_repeater *rptr = phy_get_drvdata(phy);
>>  	struct device_node *np = rptr->dev->of_node;
>>  	struct regmap *regmap = rptr->regmap;
>> -	const u32 *init_tbl = rptr->cfg->init_tbl;
>> -	u8 tune_usb2_preem = init_tbl[TUNE_USB2_PREEM];
>> -	u8 tune_hsdisc = init_tbl[TUNE_HSDISC];
>> -	u8 tune_iusb2 = init_tbl[TUNE_IUSB2];
>>  	u32 base = rptr->base;
>> -	u32 val;
>> +	u32 poll_val;
>>  	int ret;
>> -
>> -	of_property_read_u8(np, "qcom,tune-usb2-amplitude", &tune_iusb2);
>> -	of_property_read_u8(np, "qcom,tune-usb2-disc-thres", &tune_hsdisc);
>> -	of_property_read_u8(np, "qcom,tune-usb2-preem", &tune_usb2_preem);
>> +	u8 val;
>>  
>>  	ret = regulator_bulk_enable(rptr->cfg->num_vregs, rptr->vregs);
>>  	if (ret)
>> @@ -147,21 +145,24 @@ static int eusb2_repeater_init(struct phy *phy)
>>  
>>  	regmap_write(regmap, base + EUSB2_EN_CTL1, EUSB2_RPTR_EN);
>>  
>> -	regmap_write(regmap, base + EUSB2_TUNE_EUSB_HS_COMP_CUR, init_tbl[TUNE_EUSB_HS_COMP_CUR]);
>> -	regmap_write(regmap, base + EUSB2_TUNE_EUSB_EQU, init_tbl[TUNE_EUSB_EQU]);
>> -	regmap_write(regmap, base + EUSB2_TUNE_EUSB_SLEW, init_tbl[TUNE_EUSB_SLEW]);
>> -	regmap_write(regmap, base + EUSB2_TUNE_USB2_HS_COMP_CUR, init_tbl[TUNE_USB2_HS_COMP_CUR]);
>> -	regmap_write(regmap, base + EUSB2_TUNE_USB2_EQU, init_tbl[TUNE_USB2_EQU]);
>> -	regmap_write(regmap, base + EUSB2_TUNE_USB2_SLEW, init_tbl[TUNE_USB2_SLEW]);
>> -	regmap_write(regmap, base + EUSB2_TUNE_SQUELCH_U, init_tbl[TUNE_SQUELCH_U]);
>> -	regmap_write(regmap, base + EUSB2_TUNE_RES_FSDIF, init_tbl[TUNE_RES_FSDIF]);
>> -	regmap_write(regmap, base + EUSB2_TUNE_USB2_CROSSOVER, init_tbl[TUNE_USB2_CROSSOVER]);
>> +	/* Write registers from init table */
>> +	for (int i = 0; i < rptr->cfg->init_tbl_num; i++)
>> +		regmap_write(regmap, base + rptr->cfg->init_tbl[i].reg,
>
> Init tables have TUNE_foo values in the .reg field instead of
> EUSB2_TUNE_foo, which means that writes go to a random location.

Right, stupid mistake. Thanks for spotting!

I will fix the init tables to use EUSB2_TUNE_*, and probably drop this
"enum eusb2_reg_layout" completely.

Regards
Luca

>
>> +			     rptr->cfg->init_tbl[i].value);
>>  
>> -	regmap_write(regmap, base + EUSB2_TUNE_USB2_PREEM, tune_usb2_preem);
>> -	regmap_write(regmap, base + EUSB2_TUNE_HSDISC, tune_hsdisc);
>> -	regmap_write(regmap, base + EUSB2_TUNE_IUSB2, tune_iusb2);
>> +	/* Override registers from devicetree values */
>> +	if (!of_property_read_u8(np, "qcom,tune-usb2-amplitude", &val))
>> +		regmap_write(regmap, base + EUSB2_TUNE_USB2_PREEM, val);
>>  
>> -	ret = regmap_read_poll_timeout(regmap, base + EUSB2_RPTR_STATUS, val, val & RPTR_OK, 10, 5);
>> +	if (!of_property_read_u8(np, "qcom,tune-usb2-disc-thres", &val))
>> +		regmap_write(regmap, base + EUSB2_TUNE_HSDISC, val);
>> +
>> +	if (!of_property_read_u8(np, "qcom,tune-usb2-preem", &val))
>> +		regmap_write(regmap, base + EUSB2_TUNE_IUSB2, val);
>> +
>> +	/* Wait for status OK */
>> +	ret = regmap_read_poll_timeout(regmap, base + EUSB2_RPTR_STATUS, poll_val,
>> +				       poll_val & RPTR_OK, 10, 5);
>>  	if (ret)
>>  		dev_err(rptr->dev, "initialization timed-out\n");
>>  
>> 
>> -- 
>> 2.49.0
>>