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

[Seunghun Han <kkamagui@xxxxxxxxx>]

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.

[  5.732084] tpm_crb MSFT0101:00: can't request region for resource
             [mem 0x79b4f000-0x79b4ffff]
[  5.732089] 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. 
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.
               https://lkml.org/lkml/2019/8/31/217

 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 |
+			       IORESOURCE_BUSY, IORES_DESC_ACPI_NV_STORAGE);
+	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;
-- 
2.21.0