[PATCH v2 2/2] tpm: tpm_crb: enhance resource mapping mechanism for supporting AMD's fTPM

From: Seunghun Han
Date: Mon Sep 09 2019 - 05:09:55 EST

I got an AMD system which had a Ryzen Threadripper 1950X and MSI
mainboard, and I had a problem with AMD's fTPM. My machine showed an error
message below, and the fTPM didn't work because of it.

[ÂÂ5.732084] tpm_crb MSFT0101:00: can't request region for resource
[mem 0x79b4f000-0x79b4ffff]
[ÂÂ5.732089] tpm_crb: probe of MSFT0101:00 failed with error -16

When I saw the iomem, I found two fTPM regions were in the ACPI NVS area.Â
The regions are below.

79a39000-79b6afff : ACPI Non-volatile Storage
79b4b000-79b4bfff : MSFT0101:00
79b4f000-79b4ffff : MSFT0101:00

After analyzing this issue, I found that crb_map_io() function called
devm_ioremap_resource() and it failed. The ACPI NVS didn't allow the TPM
CRB driver to assign a resource in it because a busy bit was set to
the ACPI NVS area.

To support AMD's fTPM, I added a function to check intersects between
the TPM region and ACPI NVS before it mapped the region. If some
intersects are detected, the function just calls devm_ioremap() for
a workaround. If there is no intersect, it calls devm_ioremap_resource().

Signed-off-by: Seunghun Han <kkamagui@xxxxxxxxx>
Changes in v2: fix a warning of kbuild test robot. The link is below.

drivers/char/tpm/tpm_crb.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index 14f486c23af2..6b98a3a995b7 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -450,6 +450,27 @@ static int crb_check_resource(struct acpi_resource *ares, void *data)
return 1;

+static void __iomem *crb_ioremap_resource(struct device *dev,
+ const struct resource *res)
+ int rc;
+ resource_size_t size = resource_size(res);
+ /* Broken BIOS assigns command and response buffers in ACPI NVS region.
+ * Check intersections between a resource and ACPI NVS for W/A.
+ */
+ rc = region_intersects(res->start, size, IORESOURCE_MEM |
+ if (rc != REGION_DISJOINT) {
+ dev_err(dev,
+ FW_BUG "Resource overlaps with a ACPI NVS. %pr\n",
+ res);
+ return devm_ioremap(dev, res->start, size);
+ }
+ return devm_ioremap_resource(dev, res);
static void __iomem *crb_map_res(struct device *dev, struct crb_priv *priv,
struct resource *io_res, u64 start, u32 size)
@@ -464,7 +485,7 @@ static void __iomem *crb_map_res(struct device *dev, struct crb_priv *priv,
return (void __iomem *) ERR_PTR(-EINVAL);

if (!resource_contains(io_res, &new_res))
- return devm_ioremap_resource(dev, &new_res);
+ return crb_ioremap_resource(dev, &new_res);

return priv->iobase + (new_res.start - io_res->start);
@@ -536,7 +557,7 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
goto out_early;

- priv->iobase = devm_ioremap_resource(dev, &io_res);
+ priv->iobase = crb_ioremap_resource(dev, &io_res);
if (IS_ERR(priv->iobase)) {
ret = PTR_ERR(priv->iobase);
goto out_early;