[PATCH AUTOSEL 5.11 066/104] Revert "iommu/amd: Fix performance counter initialization"

[PATCH AUTOSEL 5.11 066/104] Revert "iommu/amd: Fix performance counter initialization"

[Sasha Levin]

From: Paul Menzel <pmenzel@molgen.mpg.de>

[ Upstream commit 715601e4e36903a653cd4294dfd3ed0019101991 ]

This reverts commit 6778ff5b21bd8e78c8bd547fd66437cf2657fd9b.

The original commit tries to address an issue, where PMC power-gating
causing the IOMMU PMC pre-init test to fail on certain desktop/mobile
platforms where the power-gating is normally enabled.

There have been several reports that the workaround still does not
guarantee to work, and can add up to 100 ms (on the worst case)
to the boot process on certain platforms such as the MSI B350M MORTAR
with AMD Ryzen 3 2200G.

Therefore, revert this commit as a prelude to removing the pre-init
test.

Link: https://lore.kernel.org/linux-iommu/alpine.LNX.3.20.13.2006030935570.3181@monopod.intra.ispras.ru/
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201753
Cc: Tj (Elloe Linux) <ml.linux@elloe.vision>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Alexander Monakov <amonakov@ispras.ru>
Cc: David Coe <david.coe@live.co.uk>
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Link: https://lore.kernel.org/r/20210409085848.3908-2-suravee.suthikulpanit@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/amd/init.c | 45 ++++++++++------------------------------
 1 file changed, 11 insertions(+), 34 deletions(-)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 78339b0bb8e5..7720dcfa2b29 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -12,7 +12,6 @@
 #include <linux/acpi.h>
 #include <linux/list.h>
 #include <linux/bitmap.h>
-#include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/syscore_ops.h>
 #include <linux/interrupt.h>
@@ -255,8 +254,6 @@ static enum iommu_init_state init_state = IOMMU_START_STATE;
 static int amd_iommu_enable_interrupts(void);
 static int __init iommu_go_to_state(enum iommu_init_state state);
 static void init_device_table_dma(void);
-static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr,
-				u8 fxn, u64 *value, bool is_write);
 
 static bool amd_iommu_pre_enabled = true;
 
@@ -1715,11 +1712,13 @@ static int __init init_iommu_all(struct acpi_table_header *table)
 	return 0;
 }
 
-static void __init init_iommu_perf_ctr(struct amd_iommu *iommu)
+static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr,
+				u8 fxn, u64 *value, bool is_write);
+
+static void init_iommu_perf_ctr(struct amd_iommu *iommu)
 {
-	int retry;
 	struct pci_dev *pdev = iommu->dev;
-	u64 val = 0xabcd, val2 = 0, save_reg, save_src;
+	u64 val = 0xabcd, val2 = 0, save_reg = 0;
 
 	if (!iommu_feature(iommu, FEATURE_PC))
 		return;
@@ -1727,39 +1726,17 @@ static void __init init_iommu_perf_ctr(struct amd_iommu *iommu)
 	amd_iommu_pc_present = true;
 
 	/* save the value to restore, if writable */
-	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false) ||
-	    iommu_pc_get_set_reg(iommu, 0, 0, 8, &save_src, false))
-		goto pc_false;
-
-	/*
-	 * Disable power gating by programing the performance counter
-	 * source to 20 (i.e. counts the reads and writes from/to IOMMU
-	 * Reserved Register [MMIO Offset 1FF8h] that are ignored.),
-	 * which never get incremented during this init phase.
-	 * (Note: The event is also deprecated.)
-	 */
-	val = 20;
-	if (iommu_pc_get_set_reg(iommu, 0, 0, 8, &val, true))
+	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false))
 		goto pc_false;
 
 	/* Check if the performance counters can be written to */
-	val = 0xabcd;
-	for (retry = 5; retry; retry--) {
-		if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true) ||
-		    iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false) ||
-		    val2)
-			break;
-
-		/* Wait about 20 msec for power gating to disable and retry. */
-		msleep(20);
-	}
-
-	/* restore */
-	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true) ||
-	    iommu_pc_get_set_reg(iommu, 0, 0, 8, &save_src, true))
+	if ((iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true)) ||
+	    (iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false)) ||
+	    (val != val2))
 		goto pc_false;
 
-	if (val != val2)
+	/* restore */
+	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true))
 		goto pc_false;
 
 	pci_info(pdev, "IOMMU performance counters supported\n");
-- 
2.30.2

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[PATCH AUTOSEL 5.11 067/104] iommu/amd: Remove performance counter pre-initialization test

[Sasha Levin]

From: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>

[ Upstream commit 994d6608efe4a4c8834bdc5014c86f4bc6aceea6 ]

In early AMD desktop/mobile platforms (during 2013), when the IOMMU
Performance Counter (PMC) support was first introduced in
commit 30861ddc9cca ("perf/x86/amd: Add IOMMU Performance Counter
resource management"), there was a HW bug where the counters could not
be accessed. The result was reading of the counter always return zero.

At the time, the suggested workaround was to add a test logic prior
to initializing the PMC feature to check if the counters can be programmed
and read back the same value. This has been working fine until the more
recent desktop/mobile platforms start enabling power gating for the PMC,
which prevents access to the counters. This results in the PMC support
being disabled unnecesarily.

Unfortunatly, there is no documentation of since which generation
of hardware the original PMC HW bug was fixed. Although, it was fixed
soon after the first introduction of the PMC. Base on this, we assume
that the buggy platforms are less likely to be in used, and it should
be relatively safe to remove this legacy logic.

Link: https://lore.kernel.org/linux-iommu/alpine.LNX.3.20.13.2006030935570.3181@monopod.intra.ispras.ru/
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201753
Cc: Tj (Elloe Linux) <ml.linux@elloe.vision>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: Alexander Monakov <amonakov@ispras.ru>
Cc: David Coe <david.coe@live.co.uk>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Tested-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20210409085848.3908-3-suravee.suthikulpanit@amd.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/amd/init.c | 24 +-----------------------
 1 file changed, 1 insertion(+), 23 deletions(-)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 7720dcfa2b29..3c86b6ff978f 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -1712,33 +1712,16 @@ static int __init init_iommu_all(struct acpi_table_header *table)
 	return 0;
 }
 
-static int iommu_pc_get_set_reg(struct amd_iommu *iommu, u8 bank, u8 cntr,
-				u8 fxn, u64 *value, bool is_write);
-
 static void init_iommu_perf_ctr(struct amd_iommu *iommu)
 {
+	u64 val;
 	struct pci_dev *pdev = iommu->dev;
-	u64 val = 0xabcd, val2 = 0, save_reg = 0;
 
 	if (!iommu_feature(iommu, FEATURE_PC))
 		return;
 
 	amd_iommu_pc_present = true;
 
-	/* save the value to restore, if writable */
-	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, false))
-		goto pc_false;
-
-	/* Check if the performance counters can be written to */
-	if ((iommu_pc_get_set_reg(iommu, 0, 0, 0, &val, true)) ||
-	    (iommu_pc_get_set_reg(iommu, 0, 0, 0, &val2, false)) ||
-	    (val != val2))
-		goto pc_false;
-
-	/* restore */
-	if (iommu_pc_get_set_reg(iommu, 0, 0, 0, &save_reg, true))
-		goto pc_false;
-
 	pci_info(pdev, "IOMMU performance counters supported\n");
 
 	val = readl(iommu->mmio_base + MMIO_CNTR_CONF_OFFSET);
@@ -1746,11 +1729,6 @@ static void init_iommu_perf_ctr(struct amd_iommu *iommu)
 	iommu->max_counters = (u8) ((val >> 7) & 0xf);
 
 	return;
-
-pc_false:
-	pci_err(pdev, "Unable to read/write to IOMMU perf counter.\n");
-	amd_iommu_pc_present = false;
-	return;
 }
 
 static ssize_t amd_iommu_show_cap(struct device *dev,
-- 
2.30.2

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