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Message-ID: <abd2244b-d222-35e8-9aec-5c72ca2ace01@quicinc.com>
Date: Mon, 17 Feb 2025 18:08:35 +0800
From: "Wenbin Yao (Consultant)" <quic_wenbyao@...cinc.com>
To: Manivannan Sadhasivam <mani@...nel.org>
CC: <vkoul@...nel.org>, <kishon@...nel.org>, <p.zabel@...gutronix.de>,
<dmitry.baryshkov@...aro.org>, <abel.vesa@...aro.org>,
<quic_qianyu@...cinc.com>, <neil.armstrong@...aro.org>,
<manivannan.sadhasivam@...aro.org>, <quic_devipriy@...cinc.com>,
<konrad.dybcio@....qualcomm.com>, <linux-arm-msm@...r.kernel.org>,
<linux-phy@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] phy: qcom: qmp-pcie: Add PHY register retention
support
On 2/14/2025 10:46 PM, Manivannan Sadhasivam wrote:
> On Fri, Feb 14, 2025 at 06:45:39PM +0800, Wenbin Yao wrote:
>> From: Qiang Yu <quic_qianyu@...cinc.com>
>>
>> Some QCOM PCIe PHYs support no_csr reset. Unlike BCR reset which resets the
>> whole PHY (hardware and register), no_csr reset only resets PHY hardware
>> but retains register values, which means PHY setting can be skipped during
>> PHY init if PCIe link is enabled in booltloader and only no_csr is toggled
>> after that.
>>
>> Hence, determine whether the PHY has been enabled in bootloader by
>> verifying QPHY_START_CTRL register. If it's programmed and no_csr reset is
>> available, skip BCR reset and PHY register setting to establish the PCIe
>> link with bootloader - programmed PHY settings.
>>
>> Signed-off-by: Qiang Yu <quic_qianyu@...cinc.com>
>> Signed-off-by: Wenbin Yao <quic_wenbyao@...cinc.com>
>> ---
>> drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 96 ++++++++++++++++--------
>> 1 file changed, 63 insertions(+), 33 deletions(-)
>>
>> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
>> index 219266125cf2..b3912c1a6de8 100644
>> --- a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
>> +++ b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
>> @@ -2805,6 +2805,7 @@ struct qmp_pcie {
>>
>> const struct qmp_phy_cfg *cfg;
>> bool tcsr_4ln_config;
>> + bool skip_init;
>>
>> void __iomem *serdes;
>> void __iomem *pcs;
>> @@ -3976,7 +3977,9 @@ static int qmp_pcie_init(struct phy *phy)
>> {
>> struct qmp_pcie *qmp = phy_get_drvdata(phy);
>> const struct qmp_phy_cfg *cfg = qmp->cfg;
>> + void __iomem *pcs = qmp->pcs;
>> int ret;
>> + bool phy_initialized;
>>
>> ret = regulator_bulk_enable(cfg->num_vregs, qmp->vregs);
>> if (ret) {
>> @@ -3984,10 +3987,18 @@ static int qmp_pcie_init(struct phy *phy)
>> return ret;
>> }
>>
>> - ret = reset_control_bulk_assert(cfg->num_resets, qmp->resets);
>> - if (ret) {
>> - dev_err(qmp->dev, "reset assert failed\n");
>> - goto err_disable_regulators;
>> + phy_initialized = !!(readl(pcs + cfg->regs[QPHY_START_CTRL]));
>> + qmp->skip_init = qmp->nocsr_reset && phy_initialized;
>> + /*
>> + * Toggle BCR reset for phy that doesn't support no_csr
> s/phy/PHY. Here and below.
Will use PHY instead.
>
>> + * reset or has not been initialized
>> + */
>> + if (!qmp->skip_init) {
>> + ret = reset_control_bulk_assert(cfg->num_resets, qmp->resets);
>> + if (ret) {
>> + dev_err(qmp->dev, "reset assert failed\n");
>> + goto err_disable_regulators;
>> + }
>> }
>>
>> ret = reset_control_assert(qmp->nocsr_reset);
>> @@ -3998,10 +4009,12 @@ static int qmp_pcie_init(struct phy *phy)
>>
>> usleep_range(200, 300);
>>
>> - ret = reset_control_bulk_deassert(cfg->num_resets, qmp->resets);
>> - if (ret) {
>> - dev_err(qmp->dev, "reset deassert failed\n");
>> - goto err_assert_reset;
>> + if (!qmp->skip_init) {
>> + ret = reset_control_bulk_deassert(cfg->num_resets, qmp->resets);
>> + if (ret) {
>> + dev_err(qmp->dev, "reset deassert failed\n");
>> + goto err_assert_reset;
>> + }
>> }
>>
>> ret = clk_bulk_prepare_enable(ARRAY_SIZE(qmp_pciephy_clk_l), qmp->clks);
>> @@ -4011,7 +4024,8 @@ static int qmp_pcie_init(struct phy *phy)
>> return 0;
>>
>> err_assert_reset:
>> - reset_control_bulk_assert(cfg->num_resets, qmp->resets);
>> + if (!qmp->skip_init)
>> + reset_control_bulk_assert(cfg->num_resets, qmp->resets);
>> err_disable_regulators:
>> regulator_bulk_disable(cfg->num_vregs, qmp->vregs);
>>
>> @@ -4023,7 +4037,10 @@ static int qmp_pcie_exit(struct phy *phy)
>> struct qmp_pcie *qmp = phy_get_drvdata(phy);
>> const struct qmp_phy_cfg *cfg = qmp->cfg;
>>
>> - reset_control_bulk_assert(cfg->num_resets, qmp->resets);
>> + if (!qmp->nocsr_reset)
>> + reset_control_bulk_assert(cfg->num_resets, qmp->resets);
>> + else
>> + reset_control_assert(qmp->nocsr_reset);
> I'd flip the if condition for readability:
>
> if (qmp->nocsr_reset)
> ...
> else
> ...
Will flip the if condition.
>>
>> clk_bulk_disable_unprepare(ARRAY_SIZE(qmp_pciephy_clk_l), qmp->clks);
>>
>> @@ -4042,16 +4059,22 @@ static int qmp_pcie_power_on(struct phy *phy)
>> unsigned int mask, val;
>> int ret;
>>
>> - qphy_setbits(pcs, cfg->regs[QPHY_PCS_POWER_DOWN_CONTROL],
>> - cfg->pwrdn_ctrl);
>> + /*
>> + * Write CSR register for phy that doesn't support no_csr
>> + * reset or has not been initialized
>> + */
>> + if (!qmp->skip_init) {
> How about:
> if (qmp->skip_init)
> goto skip_phy_init;
>
> This is my personal preference btw. If anyone feels the other way, feel free
> to drop this suggestion.
Will use goto statements.
>
>> + qphy_setbits(pcs, cfg->regs[QPHY_PCS_POWER_DOWN_CONTROL],
>> + cfg->pwrdn_ctrl);
>>
>> - if (qmp->mode == PHY_MODE_PCIE_RC)
>> - mode_tbls = cfg->tbls_rc;
>> - else
>> - mode_tbls = cfg->tbls_ep;
>> + if (qmp->mode == PHY_MODE_PCIE_RC)
>> + mode_tbls = cfg->tbls_rc;
>> + else
>> + mode_tbls = cfg->tbls_ep;
>>
>> - qmp_pcie_init_registers(qmp, &cfg->tbls);
>> - qmp_pcie_init_registers(qmp, mode_tbls);
>> + qmp_pcie_init_registers(qmp, &cfg->tbls);
>> + qmp_pcie_init_registers(qmp, mode_tbls);
>> + }
>>
>> ret = clk_bulk_prepare_enable(qmp->num_pipe_clks, qmp->pipe_clks);
>> if (ret)
>> @@ -4063,15 +4086,16 @@ static int qmp_pcie_power_on(struct phy *phy)
>> goto err_disable_pipe_clk;
>> }
>>
>> - /* Pull PHY out of reset state */
>> - qphy_clrbits(pcs, cfg->regs[QPHY_SW_RESET], SW_RESET);
>> + if (!qmp->skip_init) {
> if (qmp->skip_init)
> goto skip_serdes_start;
Will use goto statements.
>
>> + /* Pull PHY out of reset state */
>> + qphy_clrbits(pcs, cfg->regs[QPHY_SW_RESET], SW_RESET);
>>
>> - /* start SerDes and Phy-Coding-Sublayer */
>> - qphy_setbits(pcs, cfg->regs[QPHY_START_CTRL], SERDES_START | PCS_START);
>> -
>> - if (!cfg->skip_start_delay)
>> - usleep_range(1000, 1200);
>> + /* start SerDes and Phy-Coding-Sublayer */
>> + qphy_setbits(pcs, cfg->regs[QPHY_START_CTRL], SERDES_START | PCS_START);
>>
>> + if (!cfg->skip_start_delay)
>> + usleep_range(1000, 1200);
>> + }
>> status = pcs + cfg->regs[QPHY_PCS_STATUS];
>> mask = cfg->phy_status;
>> ret = readl_poll_timeout(status, val, !(val & mask), 200,
>> @@ -4096,16 +4120,22 @@ static int qmp_pcie_power_off(struct phy *phy)
>>
>> clk_bulk_disable_unprepare(qmp->num_pipe_clks, qmp->pipe_clks);
>>
>> - /* PHY reset */
>> - qphy_setbits(qmp->pcs, cfg->regs[QPHY_SW_RESET], SW_RESET);
>> + /* If a PHY supports no_csr reset but isn't enabled in the bootloader,
>> + * phy settings can be reused during the D3cold -> D0 cycle. So it is
> I cannot parse this sentence. If PHY is not initialized, how can you reuse the
> settings? Also what is the D3cold->D0 reference?
>
>> + * unnecessary to check qmp->skip_init.
>> + */
>> + if (!qmp->nocsr_reset) {
> if (qmp->nocsr_reset)
> goto skip_phy_reset;
>
> - Mani
>
--
With best wishes
Wenbin
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