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Message-ID: <31f071d7-db56-f032-749e-92bc387238b8@oss.qualcomm.com>
Date: Thu, 24 Apr 2025 10:41:24 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
Cc: Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
Oliver O'Halloran <oohall@...il.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Krzysztof Wilczyński <kw@...ux.com>,
Rob Herring <robh@...nel.org>, Zhou Wang <wangzhou1@...ilicon.com>,
Will Deacon <will@...nel.org>, Robert Richter <rric@...nel.org>,
Alyssa Rosenzweig <alyssa@...enzweig.io>,
Marc Zyngier <maz@...nel.org>,
Conor Dooley <conor.dooley@...rochip.com>,
Daire McNamara <daire.mcnamara@...rochip.com>, dingwei@...vell.com,
cassel@...nel.org, Lukas Wunner <lukas@...ner.de>,
linuxppc-dev@...ts.ozlabs.org, linux-pci@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v3 5/5] PCI: qcom: Add support for resetting the slot due
to link down event
On 4/24/2025 10:30 AM, Manivannan Sadhasivam wrote:
> On Fri, Apr 18, 2025 at 08:11:47AM +0530, Krishna Chaitanya Chundru wrote:
>>
>>
>> On 4/17/2025 10:46 PM, Manivannan Sadhasivam via B4 Relay wrote:
>>> From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>>>
>>> The PCIe link can go down under circumstances such as the device firmware
>>> crash, link instability, etc... When that happens, the PCIe slot needs to
>>> be reset to make it operational again. Currently, the driver is not
>>> handling the link down event, due to which the users have to restart the
>>> machine to make PCIe link operational again. So fix it by detecting the
>>> link down event and resetting the slot.
>>>
>>> Since the Qcom PCIe controllers report the link down event through the
>>> 'global' IRQ, enable the link down event by setting PARF_INT_ALL_LINK_DOWN
>>> bit in PARF_INT_ALL_MASK register.
>>>
>>> Then in the case of the event, call pci_host_handle_link_down() API
>>> in the handler to let the PCI core handle the link down condition.
>>>
>>> The API will internally call, 'pci_host_bridge::reset_slot()' callback to
>>> reset the slot in a platform specific way. So implement the callback to
>>> reset the slot by first resetting the PCIe core, followed by reinitializing
>>> the resources and then finally starting the link again.
>>>
>>> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
>>> ---
>>> drivers/pci/controller/dwc/Kconfig | 1 +
>>> drivers/pci/controller/dwc/pcie-qcom.c | 90 +++++++++++++++++++++++++++++++++-
>>> 2 files changed, 89 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/pci/controller/dwc/Kconfig b/drivers/pci/controller/dwc/Kconfig
>>> index d9f0386396edf66ad0e514a0f545ed24d89fcb6c..ce04ee6fbd99cbcce5d2f3a75ebd72a17070b7b7 100644
>>> --- a/drivers/pci/controller/dwc/Kconfig
>>> +++ b/drivers/pci/controller/dwc/Kconfig
>>> @@ -296,6 +296,7 @@ config PCIE_QCOM
>>> select PCIE_DW_HOST
>>> select CRC8
>>> select PCIE_QCOM_COMMON
>>> + select PCI_HOST_COMMON
>>> help
>>> Say Y here to enable PCIe controller support on Qualcomm SoCs. The
>>> PCIe controller uses the DesignWare core plus Qualcomm-specific
>>> diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c
>>> index dc98ae63362db0422384b1879a2b9a7dc564d091..6b18a2775e7fcde1d634b3f58327ecc7d028e4ec 100644
>>> --- a/drivers/pci/controller/dwc/pcie-qcom.c
>>> +++ b/drivers/pci/controller/dwc/pcie-qcom.c
>>> @@ -34,6 +34,7 @@
>>> #include <linux/units.h>
>>> #include "../../pci.h"
>>> +#include "../pci-host-common.h"
>>> #include "pcie-designware.h"
>>> #include "pcie-qcom-common.h"
>>> @@ -55,6 +56,7 @@
>>> #define PARF_INT_ALL_STATUS 0x224
>>> #define PARF_INT_ALL_CLEAR 0x228
>>> #define PARF_INT_ALL_MASK 0x22c
>>> +#define PARF_STATUS 0x230
>>> #define PARF_SID_OFFSET 0x234
>>> #define PARF_BDF_TRANSLATE_CFG 0x24c
>>> #define PARF_DBI_BASE_ADDR_V2 0x350
>>> @@ -130,8 +132,11 @@
>>> /* PARF_LTSSM register fields */
>>> #define LTSSM_EN BIT(8)
>>> +#define SW_CLEAR_FLUSH_MODE BIT(10)
>>> +#define FLUSH_MODE BIT(11)
>>> /* PARF_INT_ALL_{STATUS/CLEAR/MASK} register fields */
>>> +#define PARF_INT_ALL_LINK_DOWN BIT(1)
>>> #define PARF_INT_ALL_LINK_UP BIT(13)
>>> #define PARF_INT_MSI_DEV_0_7 GENMASK(30, 23)
>>> @@ -145,6 +150,9 @@
>>> /* PARF_BDF_TO_SID_CFG fields */
>>> #define BDF_TO_SID_BYPASS BIT(0)
>>> +/* PARF_STATUS fields */
>>> +#define FLUSH_COMPLETED BIT(8)
>>> +
>>> /* ELBI_SYS_CTRL register fields */
>>> #define ELBI_SYS_CTRL_LT_ENABLE BIT(0)
>>> @@ -169,6 +177,7 @@
>>> PCIE_CAP_SLOT_POWER_LIMIT_SCALE)
>>> #define PERST_DELAY_US 1000
>>> +#define FLUSH_TIMEOUT_US 100
>>> #define QCOM_PCIE_CRC8_POLYNOMIAL (BIT(2) | BIT(1) | BIT(0))
>>> @@ -274,11 +283,14 @@ struct qcom_pcie {
>>> struct icc_path *icc_cpu;
>>> const struct qcom_pcie_cfg *cfg;
>>> struct dentry *debugfs;
>>> + int global_irq;
>>> bool suspended;
>>> bool use_pm_opp;
>>> };
>>> #define to_qcom_pcie(x) dev_get_drvdata((x)->dev)
>>> +static int qcom_pcie_reset_slot(struct pci_host_bridge *bridge,
>>> + struct pci_dev *pdev);
>>> static void qcom_ep_reset_assert(struct qcom_pcie *pcie)
>>> {
>>> @@ -1263,6 +1275,8 @@ static int qcom_pcie_host_init(struct dw_pcie_rp *pp)
>>> goto err_assert_reset;
>>> }
>>> + pp->bridge->reset_slot = qcom_pcie_reset_slot;
>>> +
>>> return 0;
>>> err_assert_reset:
>>> @@ -1300,6 +1314,73 @@ static const struct dw_pcie_host_ops qcom_pcie_dw_ops = {
>>> .post_init = qcom_pcie_host_post_init,
>>> };
>>> +static int qcom_pcie_reset_slot(struct pci_host_bridge *bridge,
>>> + struct pci_dev *pdev)
>>> +{
>>> + struct pci_bus *bus = bridge->bus;
>>> + struct dw_pcie_rp *pp = bus->sysdata;
>>> + struct dw_pcie *pci = to_dw_pcie_from_pp(pp);
>>> + struct qcom_pcie *pcie = to_qcom_pcie(pci);
>>> + struct device *dev = pcie->pci->dev;
>>> + u32 val;
>>> + int ret;
>>> +
>>> + /* Wait for the pending transactions to be completed */
>>> + ret = readl_relaxed_poll_timeout(pcie->parf + PARF_STATUS, val,
>>> + val & FLUSH_COMPLETED, 10,
>>> + FLUSH_TIMEOUT_US);
>>> + if (ret) {
>>> + dev_err(dev, "Flush completion failed: %d\n", ret);
>>> + goto err_host_deinit;
>>> + }
>>> +
>>> + /* Clear the FLUSH_MODE to allow the core to be reset */
>>> + val = readl(pcie->parf + PARF_LTSSM);
>>> + val |= SW_CLEAR_FLUSH_MODE;
>>> + writel(val, pcie->parf + PARF_LTSSM);
>>> +
>>> + /* Wait for the FLUSH_MODE to clear */
>>> + ret = readl_relaxed_poll_timeout(pcie->parf + PARF_LTSSM, val,
>>> + !(val & FLUSH_MODE), 10,
>>> + FLUSH_TIMEOUT_US);
>>> + if (ret) {
>>> + dev_err(dev, "Flush mode clear failed: %d\n", ret);
>>> + goto err_host_deinit;
>>> + }
>>> +
>>> + qcom_pcie_host_deinit(pp);
>>> +
>>> + ret = qcom_pcie_host_init(pp);
>>> + if (ret) {
>>> + dev_err(dev, "Host init failed\n");
>>> + return ret;
>>> + }
>>> +
>>> + ret = dw_pcie_setup_rc(pp);
>>> + if (ret)
>>> + goto err_host_deinit;
>>> +
>>> + /*
>>> + * Re-enable global IRQ events as the PARF_INT_ALL_MASK register is
>>> + * non-sticky.
>>> + */
>>> + if (pcie->global_irq)
>>> + writel_relaxed(PARF_INT_ALL_LINK_UP | PARF_INT_ALL_LINK_DOWN |
>>> + PARF_INT_MSI_DEV_0_7, pcie->parf + PARF_INT_ALL_MASK);
>> do we need to enable linkup again here, since all the devices are
>> enumerated previously, the linkup irq will do a rescan again which is
>> not needed.
>
> Right. I was trying to keep the irq enablement on par with probe(), but LINK_UP
> is strictly not needed. I will drop it.
>
>> Instead of linkup we update icc & opp bandwidths after
>> dw_pcie_wait_for_link() in the below.
>>
>
> Why do we need to update ICC and OPP?
After link retrain, if the link data rate has reduced due to some
electrical issue or some other reason we may need to update the icc and
opp votings here.
- Krishna Chaitanya.
>
> - Mani
>
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