[PATCH] ARM: mach-imx: tzasc: keep default region 0 secure settings for i.MX8M

[Marco Felsch <m.felsch@pengutronix.de>]

The TZC-380 region 0 is the TZC default (fallback) region. This region
is used if access to a certain DRAM address was done which isn't
configured by any other region (see [1] for more information). Region 0
covers the complete AXI space from 0x0 to AXI-bus width. The access is
secure-only after reset.

The TZC-380 is not memory alias aware (see [1] for more information) and
due to the DDR controller, the i.MX8M allows memory alias access.

Configuring region 0 as secure + non-secure RW access opens the
potential security risk of allowing access to secure only memory e.g.
TEE memory area if the TEE didn't configure all memory aliases for its
memory. Because in such case region 0 could be used as fallback if an
attackers access the TEE memory via memory aliases.

Don't reconfigure TZC-380 default region 0 to allow secure and
non-secure access and instead setup an early non-secure region 1 which
covers the complete ram <= 4G size to fix this.

[1] https://developer.arm.com/documentation/ddi0431/c

Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
---
 arch/arm/mach-imx/tzasc.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/arch/arm/mach-imx/tzasc.c b/arch/arm/mach-imx/tzasc.c
index 0fe7f6eb7f4a..31664bbf2b39 100644
--- a/arch/arm/mach-imx/tzasc.c
+++ b/arch/arm/mach-imx/tzasc.c
@@ -345,6 +345,7 @@ bool imx6_can_access_tzasc(void)
 void imx8m_tzc380_init(void)
 {
 	u32 __iomem *gpr = IOMEM(MX8M_IOMUXC_GPR_BASE_ADDR);
+	resource_size_t ram_sz;
 
 	/* Enable TZASC and lock setting */
 	setbits_le32(&gpr[10], GPR_TZASC_EN);
@@ -364,13 +365,21 @@ void imx8m_tzc380_init(void)
 	if (cpu_is_mx8mn() || cpu_is_mx8mp())
 		setbits_le32(&gpr[10], GPR_TZASC_ID_SWAP_BYPASS_LOCK);
 
+	/* All i.MX8M do have a 32-bit bus width except for the i.MX8M Nano */
+	ram_sz = imx8m_barebox_earlymem_size(32);
+	if (cpu_is_mx8mn())
+		ram_sz = imx8m_barebox_earlymem_size(16);
+
 	/*
-	 * set Region 0 attribute to allow secure and non-secure
-	 * read/write permission. Found some masters like usb dwc3
-	 * controllers can't work with secure memory.
+	 * Setup Region 1 to cover complete earlymem size, to  allow non-secure
+	 * read/write permission. Found some masters like usb dwc3 controllers
+	 * can't work with secure memory.
+	 *
+	 * According to upstream OP-TEE and TF-A the TZC-380 reagion base
+	 * address starts at 0x0 and not at MX8M_DDR_CSD1_BASE_ADDR.
 	 */
-	writel(MX8M_TZASC_REGION_ATTRIBUTES_0_SP,
-		   MX8M_TZASC_REGION_ATTRIBUTES_0);
+	imx_tzc380_init_and_setup(IOMEM(MX8M_TZASC_BASE_ADDR), 1,
+				  0, ram_sz, TZC380_REGION_SP_NS_RW);
 }
 
 bool imx8m_tzc380_is_enabled(void)
-- 
2.47.2