Re: [PATCH] ipmi:ssif: Fix double probe from tryacpi and trydmi

From: Corey Minyard
Date: Thu Mar 08 2018 - 09:10:58 EST

On 03/07/2018 05:59 PM, Jiandi An wrote:


On 03/07/2018 07:34 AM, Corey Minyard wrote:
On 03/06/2018 11:49 PM, Jiandi An wrote:
IPMI SSIF driver's parameter tryacpi and trydmi both
are set to true. The addition of IPMI DMI driver to
create platform device for each IPMI device causes
SSIF probe to be done twice on the same SMB I2C address
for BMC. Fix is to not call trydmi if tryacpi is able
to find I2C address for BMC from SPMI ACPI table and
probe successfully.

Why are you trying to do this? Is something bad happening?

SPMI is not the preferred mechanism for detecting a device,
the preferred mechanism should be the acpi match table or
OF, followed by DMI, followed by SPMI. In fact, it might be
best to just remove SPMI.

-corey


On our ARM64 platform, SSIF is the IPMI interface for host to
BMC communication and it is described in ACPI SPMI table including
the I2C address. The driver would get the SSIF device from
IPI0001 ssif_acpi_match[] and probe. It worked fine with no issues.

Then it was reported dmidecode does not show the correct SSIF
device information including correct I2C address. So SSIF device
description is also added in SMBIOS table. It worked fine with no
issues until this patch.

0944d88 ipmi: Convert DMI handling over to a platform device

We would see error message indicating trydmi via
platform_driver_register fails with -EEXIST during boot.

[ÂÂÂ 9.385758] ipmi_ssif: probe of dmi-ipmi-ssif.0 failed with error -17

This is because tryacpi ran first and successfully completed
new_ssif_client() (which adds address to ssif_info) and eventually
ssif_probe()

ssif_tryacpi
ÂÂÂ spmi_find_bmc()
ÂÂÂÂÂÂÂ try_init_spmi()
ÂÂÂÂÂÂÂÂÂÂÂ new_ssif_client()

Since both tryacpi and trydmi are set to true as module parameter
with no permission and not exposed to /sys/module/ipmi_ssif/parameters,
it triggers the following path down to dmi_ipmi_probe() and
new_ssif_client() which fails ssif_info_find() finds the address
added to ssif_info already in the ssif_tryacpi path.

ssif_trydmi
ÂÂÂ platform_driver_register(&ipmi_driver)
ÂÂÂÂÂÂÂ __platform_driver_register()
ÂÂÂÂÂÂÂÂÂÂÂ driver_register()
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ bus_add_driver()
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ driver_attach()
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ bus_for_each_dev()
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ __driver_attach()
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ driver_probe_device()
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ ssif_platform_probe()
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dmi_ipmi_probe()
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ new_ssif_client()

Are you suggesting to not do tryacpi at all and just rely on
trydmi?

Basically, yes. SPMI is really designed for early detection of interfaces
before ACPI proper comes up. You should have the IPMI device in your
ACPI tree.

My inclination is to remove SPMI support from the IPMI driver.

-corey


I was looking at the following patch to understand more about
the added ipmi_dmi driver.

9f88145 ipmi: Create a platform device for a DMI-specified IPMI interface

It's creating a platform device for each IPMI device in the DMI
table including SSIF device, for auto-loading IPMI devices from
SMBIOS tables.

Are you suggesting removing SSIF device description from ACPI
SPMI table and remove ssif_tryacpi logic all together?

But the commit description mentions ...

"This also adds the ability to extract the slave address from
the SMBIOS tables, so that when the driver uses ACPI-specified
interfaces, it can still extract the slave address from SMBIOS."

This made me think SSIF driver can still use ACPI-specified
interface. It made me think it implies SSIF device can be
described in ACPI SPMI table and SMBIOS table. Both spec
did not say they cannot.

What's your recommended way of fixing this double probing?

Thanks



Signed-off-by: Jiandi An <anjiandi@xxxxxxxxxxxxxx>
---
 drivers/char/ipmi/ipmi_ssif.c | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c
index 9d3b0fa..5c57363 100644
--- a/drivers/char/ipmi/ipmi_ssif.c
+++ b/drivers/char/ipmi/ipmi_ssif.c
@@ -1981,29 +1981,41 @@ static int try_init_spmi(struct SPMITable *spmi)
ÂÂÂÂÂ return new_ssif_client(myaddr, NULL, 0, 0, SI_SPMI, NULL);
 }
-static void spmi_find_bmc(void)
+static int spmi_find_bmc(void)
 {
ÂÂÂÂÂ acpi_statusÂÂÂÂÂ status;
ÂÂÂÂÂ struct SPMITable *spmi;
ÂÂÂÂÂ intÂÂÂÂÂÂÂÂÂÂÂÂÂ i;
+ÂÂÂ intÂÂÂÂÂÂÂÂÂÂÂÂÂ rc = 0;
ÂÂÂÂÂ if (acpi_disabled)
-ÂÂÂÂÂÂÂ return;
+ÂÂÂÂÂÂÂ return -EPERM;
ÂÂÂÂÂ if (acpi_failure)
-ÂÂÂÂÂÂÂ return;
+ÂÂÂÂÂÂÂ return -ENODEV;
ÂÂÂÂÂ for (i = 0; ; i++) {
ÂÂÂÂÂÂÂÂÂ status = acpi_get_table(ACPI_SIG_SPMI, i+1,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ (struct acpi_table_header **)&spmi);
-ÂÂÂÂÂÂÂ if (status != AE_OK)
-ÂÂÂÂÂÂÂÂÂÂÂ return;
+ÂÂÂÂÂÂÂ if (status != AE_OK) {
+ÂÂÂÂÂÂÂÂÂÂÂ if (i == 0)
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return -ENODEV;
+ÂÂÂÂÂÂÂÂÂÂÂ else
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return 0;
+ÂÂÂÂÂÂÂ }
-ÂÂÂÂÂÂÂ try_init_spmi(spmi);
+ÂÂÂÂÂÂÂ rc = try_init_spmi(spmi);
+ÂÂÂÂÂÂÂ if (rc)
+ÂÂÂÂÂÂÂÂÂÂÂ return rc;
ÂÂÂÂÂ }
+
+ÂÂÂ return 0;
 }
 #else
-static void spmi_find_bmc(void) { }
+static int spmi_find_bmc(void)
+{
+ÂÂÂ return -ENODEV;
+}
 #endif
 #ifdef CONFIG_DMI
@@ -2104,12 +2116,13 @@ static int init_ipmi_ssif(void)
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ addr[i]);
ÂÂÂÂÂ }
-ÂÂÂ if (ssif_tryacpi)
+ÂÂÂ if (ssif_tryacpi) {
ÂÂÂÂÂÂÂÂÂ ssif_i2c_driver.driver.acpi_match_tableÂÂÂ =
ÂÂÂÂÂÂÂÂÂÂÂÂÂ ACPI_PTR(ssif_acpi_match);
-
-ÂÂÂ if (ssif_tryacpi)
-ÂÂÂÂÂÂÂ spmi_find_bmc();
+ÂÂÂÂÂÂÂ rv = spmi_find_bmc();
+ÂÂÂÂÂÂÂ if (!rv)
+ÂÂÂÂÂÂÂÂÂÂÂ ssif_trydmi = false;
+ÂÂÂ }
ÂÂÂÂÂ if (ssif_trydmi) {
ÂÂÂÂÂÂÂÂÂ rv = platform_driver_register(&ipmi_driver);