Subject: Re: [PATCH 2/6] powerpc/eeh: Check PCIe link after reset

From: Gavin Shan <[email-masked]>
Date: Wed, 26 Jun 2013 07:54:41 +0800

On Tue, Jun 25, 2013 at 09:58:40PM +1000, Benjamin Herrenschmidt wrote:
>On Tue, 2013-06-25 at 18:00 +0800, Gavin Shan wrote:
>> After reset (e.g. complete reset) in order to bring the fenced PHB
>> back, the PCIe link might not be ready yet. The patch intends to
>> make sure the PCIe link is ready before accessing its subordinate
>> PCI devices. The patch also fixes that wrong values restored to
>> PCI_COMMAND register for PCI bridges.
>
>This should also help if we end up doing a full reset for ER cases
>right ?
>
>IE, in a setup with PHB -> device (no switch), if the device driver
>requests a fundamental reset, we should do a PERST at the PHB level (are
>we ?) and thus restore things in a similar way.
>

Yes, you're right. We will do PERST if the device driver requests
fundamental reset on the root port. Otherwise, no matter which
type of reset (fundamental or hot) the device driver requests,
the upstream bridge got hot reset. Anyway, the piece of code
(checking PCIe link) is possiblly applied to ER case.

Thanks,
Gavin

>> Signed-off-by: Gavin Shan <[email-masked]>
>> ---
>>  arch/powerpc/kernel/eeh_pe.c |  157 ++++++++++++++++++++++++++++++++++++++----
>>  1 files changed, 144 insertions(+), 13 deletions(-)
>> 
>> diff --git a/arch/powerpc/kernel/eeh_pe.c b/arch/powerpc/kernel/eeh_pe.c
>> index 55943fc..016588a 100644
>> --- a/arch/powerpc/kernel/eeh_pe.c
>> +++ b/arch/powerpc/kernel/eeh_pe.c
>> @@ -22,6 +22,7 @@
>>   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
>>   */
>>  
>> +#include <linux/delay.h>
>>  #include <linux/export.h>
>>  #include <linux/gfp.h>
>>  #include <linux/init.h>
>> @@ -567,30 +568,132 @@ void eeh_pe_state_clear(struct eeh_pe *pe, int state)
>>  	eeh_pe_traverse(pe, __eeh_pe_state_clear, &state);
>>  }
>>  
>> -/**
>> - * eeh_restore_one_device_bars - Restore the Base Address Registers for one device
>> - * @data: EEH device
>> - * @flag: Unused
>> +/*
>> + * Some PCI bridges (e.g. PLX bridges) have primary/secondary
>> + * buses assigned explicitly by firmware, and we probably have
>> + * lost that after reset. So we have to delay the check until
>> + * the PCI-CFG registers have been restored for the parent
>> + * bridge.
>>   *
>> - * Loads the PCI configuration space base address registers,
>> - * the expansion ROM base address, the latency timer, and etc.
>> - * from the saved values in the device node.
>> + * Don't use normal PCI-CFG accessors, which probably has been
>> + * blocked on normal path during the stage. So we need utilize
>> + * eeh operations, which is always permitted.
>>   */
>> -static void *eeh_restore_one_device_bars(void *data, void *flag)
>> +static void eeh_bridge_check_link(struct pci_dev *pdev,
>> +				  struct device_node *dn)
>> +{
>> +	int cap;
>> +	uint32_t val;
>> +	int timeout = 0;
>> +
>> +	/*
>> +	 * We only check root port and downstream ports of
>> +	 * PCIe switches
>> +	 */
>> +	if (!pci_is_pcie(pdev) ||
>> +	    (pci_pcie_type(pdev) != PCI_EXP_TYPE_ROOT_PORT &&
>> +	     pci_pcie_type(pdev) != PCI_EXP_TYPE_DOWNSTREAM))
>> +		return;
>> +
>> +	pr_debug("%s: Check PCIe link for %s ...\n",
>> +		 __func__, pci_name(pdev));
>> +
>> +	/* Check slot status */
>> +	cap = pdev->pcie_cap;
>> +	eeh_ops->read_config(dn, cap + PCI_EXP_SLTSTA, 2, &val);
>> +	if (!(val & PCI_EXP_SLTSTA_PDS)) {
>> +		pr_debug("  No card in the slot (0x%04x) !\n", val);
>> +		return;
>> +	}
>> +
>> +	/* Check power status if we have the capability */
>> +	eeh_ops->read_config(dn, cap + PCI_EXP_SLTCAP, 2, &val);
>> +	if (val & PCI_EXP_SLTCAP_PCP) {
>> +		eeh_ops->read_config(dn, cap + PCI_EXP_SLTCTL, 2, &val);
>> +		if (val & PCI_EXP_SLTCTL_PCC) {
>> +			pr_debug("  In power-off state, power it on ...\n");
>> +			val &= ~(PCI_EXP_SLTCTL_PCC | PCI_EXP_SLTCTL_PIC);
>> +			val |= (0x0100 & PCI_EXP_SLTCTL_PIC);
>> +			eeh_ops->write_config(dn, cap + PCI_EXP_SLTCTL, 2, val);
>> +			msleep(2 * 1000);
>> +		}
>> +	}
>> +
>> +	/* Enable link */
>> +	eeh_ops->read_config(dn, cap + PCI_EXP_LNKCTL, 2, &val);
>> +	val &= ~PCI_EXP_LNKCTL_LD;
>> +	eeh_ops->write_config(dn, cap + PCI_EXP_LNKCTL, 2, val);
>> +
>> +	/* Check link */
>> +	eeh_ops->read_config(dn, cap + PCI_EXP_LNKCAP, 4, &val);
>> +	if (!(val & PCI_EXP_LNKCAP_DLLLARC)) {
>> +		pr_debug("  No link reporting capability (0x%08x) \n", val);
>> +		msleep(1000);
>> +		return;
>> +	}
>> +
>> +	/* Wait the link is up until timeout (5s) */
>> +	timeout = 0;
>> +	while (timeout < 5000) {
>> +		msleep(20);
>> +		timeout += 20;
>> +
>> +		eeh_ops->read_config(dn, cap + PCI_EXP_LNKSTA, 2, &val);
>> +		if (val & PCI_EXP_LNKSTA_DLLLA)
>> +			break;
>> +	}
>> +
>> +	if (val & PCI_EXP_LNKSTA_DLLLA)
>> +		pr_debug("  Link up (%s)\n",
>> +			 (val & PCI_EXP_LNKSTA_CLS_2_5GB) ? "2.5GB" : "5GB");
>> +	else
>> +		pr_debug("  Link not ready (0x%04x)\n", val);
>> +}
>> +
>> +#define BYTE_SWAP(OFF)	(8*((OFF)/4)+3-(OFF))
>> +#define SAVED_BYTE(OFF)	(((u8 *)(edev->config_space))[BYTE_SWAP(OFF)])
>> +
>> +static void eeh_restore_bridge_bars(struct pci_dev *pdev,
>> +				    struct eeh_dev *edev,
>> +				    struct device_node *dn)
>> +{
>> +	int i;
>> +
>> +	/*
>> +	 * Device BARs: 0x10 - 0x18
>> +	 * Bus numbers and windows: 0x18 - 0x30
>> +	 */
>> +	for (i = 4; i < 13; i++)
>> +		eeh_ops->write_config(dn, i*4, 4, edev->config_space[i]);
>> +	/* Rom: 0x38 */
>> +	eeh_ops->write_config(dn, 14*4, 4, edev->config_space[14]);
>> +
>> +	/* Cache line & Latency timer: 0xC 0xD */
>> +	eeh_ops->write_config(dn, PCI_CACHE_LINE_SIZE, 1,
>> +                SAVED_BYTE(PCI_CACHE_LINE_SIZE));
>> +        eeh_ops->write_config(dn, PCI_LATENCY_TIMER, 1,
>> +                SAVED_BYTE(PCI_LATENCY_TIMER));
>> +	/* Max latency, min grant, interrupt ping and line: 0x3C */
>> +	eeh_ops->write_config(dn, 15*4, 4, edev->config_space[15]);
>> +
>> +	/* PCI Command: 0x4 */
>> +	eeh_ops->write_config(dn, PCI_COMMAND, 4, edev->config_space[1]);
>> +
>> +	/* Check the PCIe link is ready */
>> +	eeh_bridge_check_link(pdev, dn);
>> +}
>> +
>> +static void eeh_restore_device_bars(struct eeh_dev *edev,
>> +				    struct device_node *dn)
>>  {
>>  	int i;
>>  	u32 cmd;
>> -	struct eeh_dev *edev = (struct eeh_dev *)data;
>> -	struct device_node *dn = eeh_dev_to_of_node(edev);
>>  
>>  	for (i = 4; i < 10; i++)
>>  		eeh_ops->write_config(dn, i*4, 4, edev->config_space[i]);
>>  	/* 12 == Expansion ROM Address */
>>  	eeh_ops->write_config(dn, 12*4, 4, edev->config_space[12]);
>>  
>> -#define BYTE_SWAP(OFF) (8*((OFF)/4)+3-(OFF))
>> -#define SAVED_BYTE(OFF) (((u8 *)(edev->config_space))[BYTE_SWAP(OFF)])
>> -
>>  	eeh_ops->write_config(dn, PCI_CACHE_LINE_SIZE, 1,
>>  		SAVED_BYTE(PCI_CACHE_LINE_SIZE));
>>  	eeh_ops->write_config(dn, PCI_LATENCY_TIMER, 1,
>> @@ -613,6 +716,34 @@ static void *eeh_restore_one_device_bars(void *data, void *flag)
>>  	else
>>  		cmd &= ~PCI_COMMAND_SERR;
>>  	eeh_ops->write_config(dn, PCI_COMMAND, 4, cmd);
>> +}
>> +
>> +/**
>> + * eeh_restore_one_device_bars - Restore the Base Address Registers for one device
>> + * @data: EEH device
>> + * @flag: Unused
>> + *
>> + * Loads the PCI configuration space base address registers,
>> + * the expansion ROM base address, the latency timer, and etc.
>> + * from the saved values in the device node.
>> + */
>> +static void *eeh_restore_one_device_bars(void *data, void *flag)
>> +{
>> +	struct pci_dev *pdev = NULL;
>> +	struct eeh_dev *edev = (struct eeh_dev *)data;
>> +	struct device_node *dn = eeh_dev_to_of_node(edev);
>> +
>> +	/* Trace the PCI bridge */
>> +	if (eeh_probe_mode_dev()) {
>> +		pdev = eeh_dev_to_pci_dev(edev);
>> +		if (pdev->hdr_type != PCI_HEADER_TYPE_BRIDGE)
>> +                        pdev = NULL;
>> +        }
>> +
>> +	if (pdev)
>> +		eeh_restore_bridge_bars(pdev, edev, dn);
>> +	else
>> +		eeh_restore_device_bars(edev, dn);
>>  
>>  	return NULL;
>>  }
>
>