Re: [PATCH V3 1/2] pseries/eeh: Handle RTAS delay requests in configure_bridge

[Gavin Shan <gwshan@linux.vnet.ibm.com>]

On Thu, Apr 07, 2016 at 04:28:26PM +1000, Russell Currey wrote:
>In the "ibm,configure-pe" and "ibm,configure-bridge" RTAS calls, the
>spec states that values of 9900-9905 can be returned, indicating that
>software should delay for 10^x (where x is the last digit, i.e. 990x)
>milliseconds and attempt the call again. Currently, the kernel doesn't
>know about this, and respecting it fixes some PCI failures when the
>hypervisor is busy.
>
>The delay is capped at 0.2 seconds.
>
>Cc: <stable@vger.kernel.org> # 3.10+
>Signed-off-by: Russell Currey <ruscur@russell.cc>

Acked-by: Gavin Shan <gwshan@linux.vnet.ibm.com>

>---
>V3 changelog:
> - Refactorings and rewordings thanks to Gavin
> - Treat return values >9902 as 9902 thanks to Tyrel
>---
> arch/powerpc/platforms/pseries/eeh_pseries.c | 51 ++++++++++++++++++++--------
> 1 file changed, 36 insertions(+), 15 deletions(-)
>
>diff --git a/arch/powerpc/platforms/pseries/eeh_pseries.c b/arch/powerpc/platforms/pseries/eeh_pseries.c
>index ac3ffd9..405baaf 100644
>--- a/arch/powerpc/platforms/pseries/eeh_pseries.c
>+++ b/arch/powerpc/platforms/pseries/eeh_pseries.c
>@@ -615,29 +615,50 @@ static int pseries_eeh_configure_bridge(struct eeh_pe *pe)
> {
> 	int config_addr;
> 	int ret;
>+	/* Waiting 0.2s maximum before skipping configuration */
>+	int max_wait = 200;
> 
> 	/* Figure out the PE address */
> 	config_addr = pe->config_addr;
> 	if (pe->addr)
> 		config_addr = pe->addr;
> 
>-	/* Use new configure-pe function, if supported */
>-	if (ibm_configure_pe != RTAS_UNKNOWN_SERVICE) {
>-		ret = rtas_call(ibm_configure_pe, 3, 1, NULL,
>-				config_addr, BUID_HI(pe->phb->buid),
>-				BUID_LO(pe->phb->buid));
>-	} else if (ibm_configure_bridge != RTAS_UNKNOWN_SERVICE) {
>-		ret = rtas_call(ibm_configure_bridge, 3, 1, NULL,
>-				config_addr, BUID_HI(pe->phb->buid),
>-				BUID_LO(pe->phb->buid));
>-	} else {
>-		return -EFAULT;
>-	}
>+	while (max_wait > 0) {
>+		/* Use new configure-pe function, if supported */
>+		if (ibm_configure_pe != RTAS_UNKNOWN_SERVICE) {
>+			ret = rtas_call(ibm_configure_pe, 3, 1, NULL,
>+					config_addr, BUID_HI(pe->phb->buid),
>+					BUID_LO(pe->phb->buid));
>+		} else if (ibm_configure_bridge != RTAS_UNKNOWN_SERVICE) {
>+			ret = rtas_call(ibm_configure_bridge, 3, 1, NULL,
>+					config_addr, BUID_HI(pe->phb->buid),
>+					BUID_LO(pe->phb->buid));
>+		} else {
>+			return -EFAULT;
>+		}
> 
>-	if (ret)
>-		pr_warn("%s: Unable to configure bridge PHB#%d-PE#%x (%d)\n",
>-			__func__, pe->phb->global_number, pe->addr, ret);
>+		if (!ret)
>+			return ret;
>+
>+		/*
>+		 * If RTAS returns a delay value that's above 100ms, cut it
>+		 * down to 100ms in case firmware made a mistake.  For more
>+		 * on how these delay values work see rtas_busy_delay_time
>+		 */
>+		if (ret > RTAS_EXTENDED_DELAY_MIN+2 &&
>+		    ret <= RTAS_EXTENDED_DELAY_MAX)
>+			ret = RTAS_EXTENDED_DELAY_MIN+2;
>+
>+		max_wait -= rtas_busy_delay_time(ret);
>+
>+		if (max_wait < 0)
>+			break;
>+
>+		rtas_busy_delay(ret);
>+	}
> 
>+	pr_warn("%s: Unable to configure bridge PHB#%d-PE#%x (%d)\n",
>+		__func__, pe->phb->global_number, pe->addr, ret);
> 	return ret;
> }
> 
>-- 
>2.8.0
>
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