tpm crb: Work around BIOS's that report the wrong ACPI region size

The expectation is that the if the CRB cmd/rsp buffer falls within the
ACPI region that the entire buffer will be within the reason. Otherwise
resource reservation will fail when it crosses regions.

Work around this BIOS bug by limiting the cmd/rsp buffer to the length
of the declared ACPI region. BIOS vendors should fix this by making
the ACPI and register length declarations consistent.
Reported-by: Davide Guerri <davide.guerri@gmail.com>
Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Davide Guerri <davide.guerri@gmail.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

drivers/char/tpm/tpm_crb.c

@@ -295,6 +295,27 @@ static void __iomem *crb_map_res(struct device *dev, struct crb_priv *priv,
 	return priv->iobase + (new_res.start - io_res->start);
 }
 
+/*
+ * Work around broken BIOSs that return inconsistent values from the ACPI
+ * region vs the registers. Trust the ACPI region. Such broken systems
+ * probably cannot send large TPM commands since the buffer will be truncated.
+ */
+static u64 crb_fixup_cmd_size(struct device *dev, struct resource *io_res,
+			      u64 start, u64 size)
+{
+	if (io_res->start > start || io_res->end < start)
+		return size;
+
+	if (start + size - 1 <= io_res->end)
+		return size;
+
+	dev_err(dev,
+		FW_BUG "ACPI region does not cover the entire command/response buffer. %pr vs %llx %llx\n",
+		io_res, start, size);
+
+	return io_res->end - start + 1;
+}
+
 static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 		      struct acpi_table_tpm2 *buf)
 {
@@ -340,7 +361,8 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 	pa_high = ioread32(&priv->cca->cmd_pa_high);
 	pa_low  = ioread32(&priv->cca->cmd_pa_low);
 	cmd_pa = ((u64)pa_high << 32) | pa_low;
-	cmd_size = ioread32(&priv->cca->cmd_size);
+	cmd_size = crb_fixup_cmd_size(dev, &io_res, cmd_pa,
+				      ioread32(&priv->cca->cmd_size));
 
 	dev_dbg(dev, "cmd_hi = %X cmd_low = %X cmd_size %X\n",
 		pa_high, pa_low, cmd_size);
@@ -353,7 +375,8 @@ static int crb_map_io(struct acpi_device *device, struct crb_priv *priv,
 
 	memcpy_fromio(&rsp_pa, &priv->cca->rsp_pa, 8);
 	rsp_pa = le64_to_cpu(rsp_pa);
-	rsp_size = ioread32(&priv->cca->rsp_size);
+	rsp_size = crb_fixup_cmd_size(dev, &io_res, rsp_pa,
+				      ioread32(&priv->cca->rsp_size));
 
 	if (cmd_pa != rsp_pa) {
 		priv->rsp = crb_map_res(dev, priv, &io_res, rsp_pa, rsp_size);