Re: [PATCH v3 5/6] PCI: qcom: Add support for host_stop_link() & host_start_link()

Manivannan Sadhasivam
2024-11-15T11:57:40Z

On Tue, Nov 12, 2024 at 08:31:37PM +0530, Krishna chaitanya chundru wrote:
> For the switches like QPS615 which needs to configure it before
> the PCIe link is established.
>
> If the link is up, the boatloader might powered and configured the
> endpoint/switch already. In that case don't touch PCIe link else
> assert the PERST# and disable LTSSM bit so that PCIe controller
> will not participate in the link training as part of host_stop_link().
>
> De-assert the PERST# and enable LTSSM bit back in host_start_link().
>
> Introduce ltssm_disable function op to stop the link training.
>
> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> ---
> drivers/pci/controller/dwc/pcie-qcom.c | 39 ++++++++++++++++++++++++++++++++++
> 1 file changed, 39 insertions(+)
>
> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
> index ef44a82be058..048aea94e319 100644
> --- a/drivers/pci/controller/dwc/pcie-qcom.c
> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
> @@ -246,6 +246,7 @@ struct qcom_pcie_ops {
> void (*host_post_init)(struct qcom_pcie *pcie);
> void (*deinit)(struct qcom_pcie *pcie);
> void (*ltssm_enable)(struct qcom_pcie *pcie);
> + void (*ltssm_disable)(struct qcom_pcie *pcie);
> int (*config_sid)(struct qcom_pcie *pcie);
> };
>
> @@ -617,6 +618,41 @@ static int qcom_pcie_post_init_1_0_0(struct qcom_pcie *pcie)
> return 0;
> }
>
> +static int qcom_pcie_host_start_link(struct dw_pcie *pci)
> +{
> + struct qcom_pcie *pcie = to_qcom_pcie(pci);
> +
> + if (!dw_pcie_link_up(pcie->pci)) {

I don't think the controller driver should worry about the bootloader
initialization. You should export dw_pcie_link_up() as a callback and call
start/stop link if only required (link not up) from the pwrctl driver.

- Mani

> + qcom_ep_reset_deassert(pcie);
> +
> + if (pcie->cfg->ops->ltssm_enable)
> + pcie->cfg->ops->ltssm_enable(pcie);
> + }
> +
> + return 0;
> +}
> +
> +static void qcom_pcie_host_stop_link(struct dw_pcie *pci)
> +{
> + struct qcom_pcie *pcie = to_qcom_pcie(pci);
> +
> + if (!dw_pcie_link_up(pcie->pci)) {
> + qcom_ep_reset_assert(pcie);
> +
> + if (pcie->cfg->ops->ltssm_disable)
> + pcie->cfg->ops->ltssm_disable(pcie);
> + }
> +}
> +
> +static void qcom_pcie_2_3_2_ltssm_disable(struct qcom_pcie *pcie)
> +{
> + u32 val;
> +
> + val = readl(pcie->parf + PARF_LTSSM);
> + val &= ~LTSSM_EN;
> + writel(val, pcie->parf + PARF_LTSSM);
> +}
> +
> static void qcom_pcie_2_3_2_ltssm_enable(struct qcom_pcie *pcie)
> {
> u32 val;
> @@ -1361,6 +1397,7 @@ static const struct qcom_pcie_ops ops_1_9_0 = {
> .host_post_init = qcom_pcie_host_post_init_2_7_0,
> .deinit = qcom_pcie_deinit_2_7_0,
> .ltssm_enable = qcom_pcie_2_3_2_ltssm_enable,
> + .ltssm_disable = qcom_pcie_2_3_2_ltssm_disable,
> .config_sid = qcom_pcie_config_sid_1_9_0,
> };
>
> @@ -1418,6 +1455,8 @@ static const struct qcom_pcie_cfg cfg_sc8280xp = {
> static const struct dw_pcie_ops dw_pcie_ops = {
> .link_up = qcom_pcie_link_up,
> .start_link = qcom_pcie_start_link,
> + .host_start_link = qcom_pcie_host_start_link,
> + .host_stop_link = qcom_pcie_host_stop_link,
> };
>
> static int qcom_pcie_icc_init(struct qcom_pcie *pcie)
>
> --
> 2.34.1
>

--
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