linux-kernel - Re: [PATCH v5 2/2] phy: qcom: qmp-pcie: Add PHY register retention support

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Message-ID: <20250314145035.h3nybvvko3ew37wl@thinkpad>
Date: Fri, 14 Mar 2025 20:20:35 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Wenbin Yao <quic_wenbyao@...cinc.com>
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,
	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 v5 2/2] phy: qcom: qmp-pcie: Add PHY register retention
 support

On Wed, Feb 26, 2025 at 06:36:00PM +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>

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>

One nit below.

> ---
>  drivers/phy/qualcomm/phy-qcom-qmp-pcie.c | 69 ++++++++++++++++++++----
>  1 file changed, 59 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c b/drivers/phy/qualcomm/phy-qcom-qmp-pcie.c
> index 219266125cf2..c3642d1807e4 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;
> @@ -3976,18 +3977,38 @@ 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;
> +	bool phy_initialized = !!(readl(pcs + cfg->regs[QPHY_START_CTRL]));
>  	int ret;
>  
> +	qmp->skip_init = qmp->nocsr_reset && phy_initialized;
> +	/*
> +	 * We need to check the existence of init sequences in two cases:
> +	 * 1. The PHY doesn't support no_csr reset.
> +	 * 2. The PHY supports no_csr reset but isn't initialized by bootloader.
> +	 * As we can't skip init in these two cases.
> +	 */
> +	if (!qmp->skip_init && !cfg->tbls.serdes_num) {
> +		dev_err(qmp->dev, "no init sequences are available\n");

"Init sequence not available\n"

> +		return -EINVAL;

-ENODATA

- Mani

-- 
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