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Date:   Fri, 27 Aug 2021 13:00:16 -0700
From:   khsieh@codeaurora.org
To:     Stephen Boyd <swboyd@chromium.org>
Cc:     agross@kernel.org, bjorn.andersson@linaro.org,
        devicetree@vger.kernel.org, robdclark@gmail.com,
        robh+dt@kernel.org, sean@poorly.run, vkoul@kernel.org,
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        linux-kernel@vger.kernel.org, kishon@ti.com, p.zabel@pengutronix.de
Subject: Re: [PATCH] phy: qcom-qmp: add support for voltage and pre emphesis
 swing
In-Reply-To: <CAE-0n52obotsMwXLHm8Fkd3+7QnXCEZgVhO_FNSY7RsbC+pbcA@mail.gmail.com>
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 <CAE-0n52obotsMwXLHm8Fkd3+7QnXCEZgVhO_FNSY7RsbC+pbcA@mail.gmail.com>
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On 2021-08-25 10:49, Stephen Boyd wrote:
> Quoting Kuogee Hsieh (2021-08-24 16:29:35)
>> Add voltage and pre emphesis swing tables so that voltage and
> 
> Is it "pre-emphasis"?
> 
>> pre emphsis swing level can be configured base on link rate.
> 
> This one is also different.
> 
>> 
>> Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
> 
> Presumably
> 
> Fixes: aff188feb5e1 ("phy: qcom-qmp: add support for sm8250-usb3-dp 
> phy")
> 
>> ---
>>  drivers/phy/qualcomm/phy-qcom-qmp.c | 95 
>> ++++++++++++++++++++++++++++++++-----
>>  1 file changed, 82 insertions(+), 13 deletions(-)
>> 
>> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp.c 
>> b/drivers/phy/qualcomm/phy-qcom-qmp.c
>> index 31036aa..52bab6e 100644
>> --- a/drivers/phy/qualcomm/phy-qcom-qmp.c
>> +++ b/drivers/phy/qualcomm/phy-qcom-qmp.c
>> @@ -1916,7 +1916,7 @@ static const struct qmp_phy_init_tbl 
>> qmp_v4_dp_tx_tbl[] = {
>>         QMP_PHY_INIT_CFG(QSERDES_V4_TX_RES_CODE_LANE_OFFSET_RX, 0x11),
>>         QMP_PHY_INIT_CFG(QSERDES_V4_TX_TX_BAND, 0x4),
>>         QMP_PHY_INIT_CFG(QSERDES_V4_TX_TX_POL_INV, 0x0a),
>> -       QMP_PHY_INIT_CFG(QSERDES_V4_TX_TX_DRV_LVL, 0x2a),
>> +       QMP_PHY_INIT_CFG(QSERDES_V4_TX_TX_DRV_LVL, 0x22),
> 
> Is 0x22 the better "default"? Can that be described in the commit text?
> 
>>         QMP_PHY_INIT_CFG(QSERDES_V4_TX_TX_EMP_POST1_LVL, 0x20),
>>  };
>> 
>> @@ -3727,6 +3727,81 @@ static int qcom_qmp_v3_dp_phy_calibrate(struct 
>> qmp_phy *qphy)
>> 
>>         return 0;
>>  }
> 
> Nitpick: Newline here please.
> 
>> +/*
>> + * 0x20 deducted from tables
>> + *
>> + * swing_value |= DP_PHY_TXn_TX_DRV_LVL_MUX_EN;
>> + * pre_emphasis_value |= DP_PHY_TXn_TX_EMP_POST1_LVL_MUX_EN;
>> +*/
>> +static const u8 qmp_dp_v4_pre_emphasis_hbr3_hbr2[4][4] = {
>> +       /* p0    p1    p2    p3 */
>> +       { 0x00, 0x0c, 0x15, 0x1b },     /* s0 */
>> +       { 0x02, 0x0e, 0x16, 0xff },     /* s1 */
>> +       { 0x02, 0x11, 0xff, 0xff },     /* s2 */
>> +       { 0x04, 0xff, 0xff, 0xff }      /* s3 */
>> +};
>> +
>> +static const u8 qmp_dp_v4_voltage_swing_hbr3_hbr2[4][4] = {
> 
> This looks the same as qmp_dp_v3_voltage_swing_hbr3_hbr2. Can that be
> used?
to avoid confuse, i like to keep them separated.
> 
>> +       /* p0    p1    p2    p3 */
>> +       { 0x02, 0x12, 0x16, 0x1a },     /* s0 */
>> +       { 0x09, 0x19, 0x1f, 0xff },     /* s1 */
>> +       { 0x10, 0x1f, 0xff, 0xff },     /* s2 */
>> +       { 0x1f, 0xff, 0xff, 0xff }      /* s3 */
>> +};
>> +
>> +static const u8 qmp_dp_v4_pre_emphasis_hbr_rbr[4][4] = {
>> +       /* p0    p1    p2    p3 */
>> +       { 0x00, 0x0e, 0x15, 0x1b },     /* s0 */
>> +       { 0x00, 0x0e, 0x15, 0xff },     /* s1 */
>> +       { 0x00, 0x0e, 0xff, 0xff },     /* s2 */
>> +       { 0x04, 0xff, 0xff, 0xff }      /* s3 */
>> +};
>> +
>> +static const u8 qmp_dp_v4_voltage_swing_hbr_rbr[4][4] = {
>> +       /* p0    p1    p2    p3 */
>> +       { 0x08, 0x0f, 0x16, 0x1f },     /* s0 */
>> +       { 0x11, 0x1e, 0x1f, 0xff },     /* s1 */
>> +       { 0x16, 0x1f, 0xff, 0xff },     /* s2 */
>> +       { 0x1f, 0xff, 0xff, 0xff }      /* s3 */
> 
> Do these comments add any value? Can we drop them?
> 
>> +};
>> +
>> +static int qcom_qmp_v4_phy_configure_dp_swing(struct qmp_phy *qphy,
>> +               unsigned int drv_lvl_reg, unsigned int emp_post_reg)
>> +{
>> +       const struct phy_configure_opts_dp *dp_opts = &qphy->dp_opts;
>> +       unsigned int v_level = 0, p_level = 0;
>> +       u8 voltage_swing_cfg, pre_emphasis_cfg;
>> +       int i;
>> +
>> +       for (i = 0; i < dp_opts->lanes; i++) {
>> +               v_level = max(v_level, dp_opts->voltage[i]);
>> +               p_level = max(p_level, dp_opts->pre[i]);
>> +       }
>> +
>> +
> 
> Nitpick: Drop extra newline.
> 
>> +       if (dp_opts->link_rate <= 2700) {
>> +               voltage_swing_cfg = 
>> qmp_dp_v4_voltage_swing_hbr_rbr[v_level][p_level];
>> +               pre_emphasis_cfg = 
>> qmp_dp_v4_pre_emphasis_hbr_rbr[v_level][p_level];
>> +       } else {
>> +               voltage_swing_cfg = 
>> qmp_dp_v4_voltage_swing_hbr3_hbr2[v_level][p_level];
>> +               pre_emphasis_cfg = 
>> qmp_dp_v4_pre_emphasis_hbr3_hbr2[v_level][p_level];
>> +       }
>> +
>> +       /* TODO: Move check to config check */
>> +       if (voltage_swing_cfg == 0xFF && pre_emphasis_cfg == 0xFF)
>> +               return -EINVAL;
>> +
>> +       /* Enable MUX to use Cursor values from these registers */
>> +       voltage_swing_cfg |= DP_PHY_TXn_TX_DRV_LVL_MUX_EN;
>> +       pre_emphasis_cfg |= DP_PHY_TXn_TX_EMP_POST1_LVL_MUX_EN;
>> +
>> +       writel(voltage_swing_cfg, qphy->tx + drv_lvl_reg);
>> +       writel(pre_emphasis_cfg, qphy->tx + emp_post_reg);
>> +       writel(voltage_swing_cfg, qphy->tx2 + drv_lvl_reg);
>> +       writel(pre_emphasis_cfg, qphy->tx2 + emp_post_reg);
> 
> This is copy/pasted from qcom_qmp_phy_configure_dp_swing() right? How
> about making a function
> 
> static int
> __qcom_qmp_phy_configure_dp_swing(struct qmp_phy *qphy,
> 				  unsigned int drv_lvl_reg,
> 				  unsigned int emp_post_reg,
> 				  const u8 **voltage_rbr_hbr,
> 				  const u8 **pre_emphasis_rbr_hbr,
> 				  const u8 **voltage_hbr3_hbr2,
> 				  const u8 **pre_emphasis_hbr3_hbr2)
> 
> that does the same stuff but allows the tables to be different.
> 
>> +
>> +       return 0;
>> +}
>> 
>>  static void qcom_qmp_v4_phy_dp_aux_init(struct qmp_phy *qphy)
>>  {
>> @@ -3757,14 +3832,7 @@ static void qcom_qmp_v4_phy_dp_aux_init(struct 
>> qmp_phy *qphy)
>> 
>>  static void qcom_qmp_v4_phy_configure_dp_tx(struct qmp_phy *qphy)
>>  {
>> -       /* Program default values before writing proper values */
>> -       writel(0x27, qphy->tx + QSERDES_V4_TX_TX_DRV_LVL);
>> -       writel(0x27, qphy->tx2 + QSERDES_V4_TX_TX_DRV_LVL);
>> -
>> -       writel(0x20, qphy->tx + QSERDES_V4_TX_TX_EMP_POST1_LVL);
>> -       writel(0x20, qphy->tx2 + QSERDES_V4_TX_TX_EMP_POST1_LVL);
>> -
>> -       qcom_qmp_phy_configure_dp_swing(qphy,
>> +       qcom_qmp_v4_phy_configure_dp_swing(qphy,
>>                         QSERDES_V4_TX_TX_DRV_LVL,
>>                         QSERDES_V4_TX_TX_EMP_POST1_LVL);
>>  }
>> @@ -3885,6 +3953,9 @@ static int 
>> qcom_qmp_v4_phy_configure_dp_phy(struct qmp_phy *qphy)
>>         writel(drvr1_en, qphy->tx2 + QSERDES_V4_TX_HIGHZ_DRVR_EN);
>>         writel(bias1_en, qphy->tx2 + 
>> QSERDES_V4_TX_TRANSCEIVER_BIAS_EN);
>> 
>> +       writel(0x0a, qphy->tx + QSERDES_V4_TX_TX_POL_INV);
>> +       writel(0x0a, qphy->tx2 + QSERDES_V4_TX_TX_POL_INV);
> 
> Is this mentioned in the commit text? Is this fixing the sequence?
> It doesn't look like we're adding tables.

add these since they are missed from HPG sequence.
> 
>> +
>>         writel(0x18, qphy->pcs + QSERDES_DP_PHY_CFG);
>>         udelay(2000);
>>         writel(0x19, qphy->pcs + QSERDES_DP_PHY_CFG);
>> @@ -3896,11 +3967,9 @@ static int 
>> qcom_qmp_v4_phy_configure_dp_phy(struct qmp_phy *qphy)
>>                         10000))
>>                 return -ETIMEDOUT;
>> 
>> -       writel(0x0a, qphy->tx + QSERDES_V4_TX_TX_POL_INV);
>> -       writel(0x0a, qphy->tx2 + QSERDES_V4_TX_TX_POL_INV);
>> 
>> -       writel(0x27, qphy->tx + QSERDES_V4_TX_TX_DRV_LVL);
>> -       writel(0x27, qphy->tx2 + QSERDES_V4_TX_TX_DRV_LVL);
>> +       writel(0x22, qphy->tx + QSERDES_V4_TX_TX_DRV_LVL);
>> +       writel(0x22, qphy->tx2 + QSERDES_V4_TX_TX_DRV_LVL);
>> 
>>         writel(0x20, qphy->tx + QSERDES_V4_TX_TX_EMP_POST1_LVL);
>>         writel(0x20, qphy->tx2 + QSERDES_V4_TX_TX_EMP_POST1_LVL);