linux-kernel - Re: [PATCH v2] PCI: qcom: fix IPQ8074 Gen2 support

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Message-ID: <20220621203211.GA1330530@bhelgaas>
Date:   Tue, 21 Jun 2022 15:32:11 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Robert Marko <robimarko@...il.com>
Cc:     svarbanov@...sol.com, agross@...nel.org,
        bjorn.andersson@...aro.org, lpieralisi@...nel.org, robh@...nel.org,
        kw@...ux.com, bhelgaas@...gle.com, p.zabel@...gutronix.de,
        jingoohan1@...il.com, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        johan+linaro@...nel.org
Subject: Re: [PATCH v2] PCI: qcom: fix IPQ8074 Gen2 support

On Tue, Jun 21, 2022 at 01:23:30PM +0200, Robert Marko wrote:
> IPQ8074 has one Gen2 and one Gen3 port, currently the Gen2 port will
> cause the system to hang as its using DBI registers in the .init
> and those are only accesible after phy_power_on().

Is the fact that IPQ8074 has both a Gen2 and a Gen3 port relevant to
this patch?  I don't see the connection.

I see that qcom_pcie_host_init() does:

  qcom_pcie_host_init
    pcie->cfg->ops->init(pcie)
    phy_power_on(pcie->phy)
    pcie->cfg->ops->post_init(pcie)

and that you're moving DBI register accesses from
qcom_pcie_init_2_3_3() to qcom_pcie_post_init_2_3_3().

But I also see DBI register accesses in other .init() functions:

  qcom_pcie_init_2_1_0
  qcom_pcie_init_1_0_0      (oddly out of order)
  qcom_pcie_init_2_3_2
  qcom_pcie_init_2_4_0

Why do these accesses not need to be moved?  I assume it's because
pcie->phy is an optional PHY and phy_power_on() does nothing on those
controllers?

Whatever the reason, I think the DBI accesses should be done
consistently in .post_init().  I see that Dmitry's previous patches
removed all those .post_init() functions, but I think the consistency
is worth having.

Perhaps we could reorder the patches so this patch comes first, moves
the DBI accesses into .post_init(), then Dmitry's patches could be
rebased on top to drop the clock handling?

> So solve this by splitting the DBI read/writes to .post_init.
> 
> Fixes: a0fd361db8e5 ("PCI: dwc: Move "dbi", "dbi2", and "addr_space" resource setup into common code")
> Signed-off-by: Robert Marko <robimarko@...il.com>
> ---
> Changes in v2:
> * Rebase onto next-20220621
> ---
>  drivers/pci/controller/dwc/pcie-qcom.c | 48 +++++++++++++++-----------
>  1 file changed, 28 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index 51fed83484af..da6d79d61397 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -1061,9 +1061,7 @@ static int qcom_pcie_init_2_3_3(struct qcom_pcie *pcie)
>  	struct qcom_pcie_resources_2_3_3 *res = &pcie->res.v2_3_3;
>  	struct dw_pcie *pci = pcie->pci;
>  	struct device *dev = pci->dev;
> -	u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
>  	int i, ret;
> -	u32 val;
>  
>  	for (i = 0; i < ARRAY_SIZE(res->rst); i++) {
>  		ret = reset_control_assert(res->rst[i]);
> @@ -1120,6 +1118,33 @@ static int qcom_pcie_init_2_3_3(struct qcom_pcie *pcie)
>  		goto err_clk_aux;
>  	}
>  
> +	return 0;
> +
> +err_clk_aux:
> +	clk_disable_unprepare(res->ahb_clk);
> +err_clk_ahb:
> +	clk_disable_unprepare(res->axi_s_clk);
> +err_clk_axi_s:
> +	clk_disable_unprepare(res->axi_m_clk);
> +err_clk_axi_m:
> +	clk_disable_unprepare(res->iface);
> +err_clk_iface:
> +	/*
> +	 * Not checking for failure, will anyway return
> +	 * the original failure in 'ret'.
> +	 */
> +	for (i = 0; i < ARRAY_SIZE(res->rst); i++)
> +		reset_control_assert(res->rst[i]);
> +
> +	return ret;
> +}
> +
> +static int qcom_pcie_post_init_2_3_3(struct qcom_pcie *pcie)
> +{
> +	struct dw_pcie *pci = pcie->pci;
> +	u16 offset = dw_pcie_find_capability(pci, PCI_CAP_ID_EXP);
> +	u32 val;
> +
>  	writel(SLV_ADDR_SPACE_SZ,
>  		pcie->parf + PCIE20_v3_PARF_SLV_ADDR_SPACE_SIZE);
>  
> @@ -1147,24 +1172,6 @@ static int qcom_pcie_init_2_3_3(struct qcom_pcie *pcie)
>  		PCI_EXP_DEVCTL2);
>  
>  	return 0;
> -
> -err_clk_aux:
> -	clk_disable_unprepare(res->ahb_clk);
> -err_clk_ahb:
> -	clk_disable_unprepare(res->axi_s_clk);
> -err_clk_axi_s:
> -	clk_disable_unprepare(res->axi_m_clk);
> -err_clk_axi_m:
> -	clk_disable_unprepare(res->iface);
> -err_clk_iface:
> -	/*
> -	 * Not checking for failure, will anyway return
> -	 * the original failure in 'ret'.
> -	 */
> -	for (i = 0; i < ARRAY_SIZE(res->rst); i++)
> -		reset_control_assert(res->rst[i]);
> -
> -	return ret;
>  }
>  
>  static int qcom_pcie_get_resources_2_7_0(struct qcom_pcie *pcie)
> @@ -1598,6 +1605,7 @@ static const struct qcom_pcie_ops ops_2_4_0 = {
>  static const struct qcom_pcie_ops ops_2_3_3 = {
>  	.get_resources = qcom_pcie_get_resources_2_3_3,
>  	.init = qcom_pcie_init_2_3_3,
> +	.post_init = qcom_pcie_post_init_2_3_3,
>  	.deinit = qcom_pcie_deinit_2_3_3,
>  	.ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
>  };
> -- 
> 2.36.1
>