Subject: Re: powerpc/pci: [PATCH 1/1]: PCIE PHB reset

From: Sam Bobroff <[email-masked]>
Date: Tue, 12 May 2020 15:28:26 +1000

On Thu, May 07, 2020 at 08:10:37AM -0500, [email-masked] wrote:
> From: Wen Xiong <[email-masked]>
> 
> Several device drivers hit EEH(Extended Error handling) when triggering
> kdump on Pseries PowerVM. This patch implemented a reset of the PHBs
> in pci general code. PHB reset stop all PCI transactions from previous
> kernel. We have tested the patch in several enviroments:
> - direct slot adapters
> - adapters under the switch
> - a VF adapter in PowerVM
> - a VF adapter/adapter in KVM guest.
> 
> Signed-off-by: Wen Xiong <[email-masked]>

Hi Wen Xiong,

I saw Oliver's review and I think he's covered the main issues I was
going to raise:
- This will run and produce some spurious errors on powernv. (I think
  distros do compile in both pseries and powernv.)
- There's a bit of code duplication but it's probably OK for this patch.

I have a few other minor comments, below:

> ---
>  arch/powerpc/platforms/pseries/pci.c | 153 +++++++++++++++++++++++++++
>  1 file changed, 153 insertions(+)
> 
> diff --git a/arch/powerpc/platforms/pseries/pci.c b/arch/powerpc/platforms/pseries/pci.c
> index 911534b89c85..aac7f00696d2 100644
> --- a/arch/powerpc/platforms/pseries/pci.c
> +++ b/arch/powerpc/platforms/pseries/pci.c
> @@ -11,6 +11,8 @@
>  #include <linux/kernel.h>
>  #include <linux/pci.h>
>  #include <linux/string.h>
> +#include <linux/crash_dump.h>
> +#include <linux/delay.h>
>  
>  #include <asm/eeh.h>
>  #include <asm/pci-bridge.h>
> @@ -354,3 +356,154 @@ int pseries_root_bridge_prepare(struct pci_host_bridge *bridge)
>  
>  	return 0;
>  }
> +
> +/**
> + * pseries_get_pdn_addr - Retrieve PHB address
> + * @pe: EEH PE
> + *
> + * Retrieve the assocated PHB address. Actually, there're 2 RTAS
> + * function calls dedicated for the purpose. We need implement
> + * it through the new function and then the old one. Besides,
> + * you should make sure the config address is figured out from
> + * FDT node before calling the function.
> + *
> + */
> +static int pseries_get_pdn_addr(struct pci_controller *phb)
> +{
> +	int ret = -1;
> +	int rets[3];
> +	int ibm_get_config_addr_info;
> +	int ibm_get_config_addr_info2;
> +	int config_addr = 0;
> +	struct pci_dn *root_pdn, *pdn;
> +
> +	ibm_get_config_addr_info2   = rtas_token("ibm,get-config-addr-info2");
> +	ibm_get_config_addr_info    = rtas_token("ibm,get-config-addr-info");
> +
> +	root_pdn = PCI_DN(phb->dn);
> +	pdn = list_first_entry(&root_pdn->child_list, struct pci_dn, list);
> +	config_addr = (pdn->busno << 16) | (pdn->devfn << 8);
> +
> +	if (ibm_get_config_addr_info2 != RTAS_UNKNOWN_SERVICE) {
> +		/*
> +		 * First of all, we need to make sure there has one PE
> +		 * associated with the device. Otherwise, PE address is
> +		 * meaningless.
> +		 */

This comment might be better if it explained how using option=0
with ibm_get_config_addr tests the PE.

> +		ret = rtas_call(ibm_get_config_addr_info2, 4, 2, rets,
> +			config_addr, BUID_HI(pdn->phb->buid),
> +			BUID_LO(pdn->phb->buid), 1);
> +		if (ret || (rets[0] == 0)) {
> +			pr_warn("%s: Failed to get address for PHB#%x-PE# "
> +				"option=%d config_addr=%x\n",
> +				__func__, pdn->phb->global_number, 1, rets[0]);
> +			return -1;
> +		}
> +
> +		/* Retrieve the associated PE config address */
> +		ret = rtas_call(ibm_get_config_addr_info2, 4, 2, rets,
> +			config_addr, BUID_HI(pdn->phb->buid),
> +			BUID_LO(pdn->phb->buid), 0);
> +		if (ret) {
> +			pr_warn("%s: Failed to get address for PHB#%x-PE# "
> +				"option=%d config_addr=%x\n",
> +				__func__, pdn->phb->global_number, 0, rets[0]);
> +			return -1;
> +		}
> +		return rets[0];
> +	}
> +
> +	if (ibm_get_config_addr_info != RTAS_UNKNOWN_SERVICE) {
> +		ret = rtas_call(ibm_get_config_addr_info, 4, 2, rets,
> +			config_addr, BUID_HI(pdn->phb->buid),
> +			BUID_LO(pdn->phb->buid), 0);
> +		if (ret || rets[0]) {
> +			pr_warn("%s: Failed to get address for PHB#%x-PE# "
> +				"config_addr=%x\n",
> +				__func__, pdn->phb->global_number, rets[0]);
> +			return -1;
> +		}
> +		return rets[0];
> +	}
> +
> +	return ret;
Can this ever return anything other than 0?

> +}
> +
> +static int __init pseries_phb_reset(void)
> +{
> +	struct pci_controller *phb;
> +	int config_addr;
> +	int ibm_set_slot_reset;
> +	int ibm_configure_pe;
> +	int ret;
> +
> +	if (is_kdump_kernel() || reset_devices) {
> +		pr_info("Issue PHB reset ...\n");
> +		ibm_set_slot_reset = rtas_token("ibm,set-slot-reset");
> +		ibm_configure_pe = rtas_token("ibm,configure-pe");
> +
> +		if (ibm_set_slot_reset == RTAS_UNKNOWN_SERVICE ||
> +				ibm_configure_pe == RTAS_UNKNOWN_SERVICE) {
> +			pr_info("%s: EEH functionality not supported\n",
> +				__func__);
> +		}
> +
> +		list_for_each_entry(phb, &hose_list, list_node) {
> +			config_addr = pseries_get_pdn_addr(phb);
> +			if (config_addr == -1)
> +				continue;
> +
> +			ret = rtas_call(ibm_set_slot_reset, 4, 1, NULL,
> +				config_addr, BUID_HI(phb->buid),
> +				BUID_LO(phb->buid), EEH_RESET_FUNDAMENTAL);
> +
> +			/* If fundamental-reset not supported, try hot-reset */
> +			if (ret == -8)
> +				ret = rtas_call(ibm_set_slot_reset, 4, 1, NULL,
> +					config_addr, BUID_HI(phb->buid),
> +					BUID_LO(phb->buid), EEH_RESET_HOT);
> +
> +			if (ret) {
> +				pr_err("%s: fail with rtas_call fundamental reset=%d\n",
> +					__func__, ret);

This error might be a bit confusing, since it's not clear if the result
came from the fundamental or hot-reset.

> +				continue;
> +			}
> +		}
> +		msleep(EEH_PE_RST_SETTLE_TIME);
> +
> +		list_for_each_entry(phb, &hose_list, list_node) {
> +			config_addr = pseries_get_pdn_addr(phb);
> +			if (config_addr == -1)
> +				continue;
> +
> +			ret = rtas_call(ibm_set_slot_reset, 4, 1, NULL,
> +				config_addr, BUID_HI(phb->buid),
> +				BUID_LO(phb->buid), EEH_RESET_DEACTIVATE);
> +			if (ret) {
> +				pr_err("%s: fail with rtas_call deactive=%d\n",
> +					__func__, ret);
> +				continue;
> +			}
> +		}
> +		msleep(EEH_PE_RST_SETTLE_TIME);
> +
> +		list_for_each_entry(phb, &hose_list, list_node) {
> +			config_addr = pseries_get_pdn_addr(phb);
> +			if (config_addr == -1)
> +				continue;
> +
> +			ret = rtas_call(ibm_configure_pe, 3, 1, NULL,
> +				config_addr, BUID_HI(phb->buid),
> +				BUID_LO(phb->buid));
> +			if (ret) {
> +				pr_err("%s: fail with rtas_call configure_pe =%d\n",
> +					__func__, ret);

These errors might be more useful if they indicated which PHB caused the
error.

> +				continue;
> +			}
> +		}
> +	}
> +
> +	return 0;
> +}
> +postcore_initcall(pseries_phb_reset);
> +
> -- 
> 2.18.1
>