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

Krishna Chaitanya Chundru
2024-11-24T01:44:31Z

On 11/15/2024 5:27 PM, Manivannan Sadhasivam wrote:
> 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.
>
Instead of exporting this API, I will try to read config space and see
if the link is up or not. if it is not up then will call these.

- Krishna Chaitanya.

> - 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
>>
>