soc/intel/cmn/fast_spi: Add API to set SPI controller VCL

This patch creates a helper function to set SPI controller VCL bit as
recommended by Intel Flash Security Specification.

BUG=b:211954778
TEST=Able to build google/brya and verified that SPI flash controller
MMIO register 0xC4 bit 30 is set.

Signed-off-by: Subrata Banik <subratabanik@google.com>
Change-Id: Ie9a12db1bab81779fd8e7db90221d08da3c65011
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63626
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marc Jones <marc@marcjonesconsulting.com>
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

src/soc/intel/common/block/fast_spi/fast_spi.c

@@ -170,6 +170,23 @@ void fast_spi_pr_dlock(void)
 	write32(spibar + SPIBAR_DLOCK, dlock);
 }
 
+/*
+ * Set FAST_SPIBAR + VSCC0 (0xC4) register VCL (bit 30).
+ */
+void fast_spi_vscc0_lock(void)
+{
+	void *spibar = fast_spi_get_bar();
+
+	/*
+	 * SPI Flash Programming Guide Section 5.5.2 describes Vendor Component Lock (VCL).
+	 * It is recommended to set the VCL bit. VCL applies to both VSCC0 and VSCC1.
+	 * Without this bit being set, it is possible to modify Host/GbE VSCC register(s),
+	 * which might results in undesired host and integrated GbE Serial Flash
+	 * functionality.
+	 */
+	setbits32(spibar + SPIBAR_SFDP0_VSCC0, SPIBAR_VSCC0_VCL);
+}
+
 /*
  * Set FAST_SPIBAR Soft Reset Data Register value.
  */

src/soc/intel/common/block/fast_spi/fast_spi_def.h

@@ -131,6 +131,13 @@
 		    (SPI_OPTYPE_1 << 2) | (SPI_OPTYPE_0))
 #define SPI_OPPREFIX ((0x50 << 8) | 0x06) /* EWSR and WREN */
 
+/*
+ * Register Offset of BIOS Vendor Specific Component Capabilities (VSCC)
+ * for Component 0 Register
+ */
+#define SPIBAR_SFDP0_VSCC0		0xc4
+#define SPIBAR_VSCC0_VCL		(1 << 30)
+
 /* Bit definitions for PTINX (0xcc) register */
 #define SPIBAR_PTINX_COMP_0		(0 << 14)
 #define SPIBAR_PTINX_COMP_1		(1 << 14)

src/soc/intel/common/block/include/intelblocks/fast_spi.h

@@ -42,6 +42,10 @@ void fast_spi_lock_bar(void);
  * FAST_SPI Protected Range (PR) registers.
  */
 void fast_spi_pr_dlock(void);
+/*
+ * Set FAST_SPIBAR + VSCC0 (0xC4) register VCL (bit 30).
+ */
+void fast_spi_vscc0_lock(void);
 /*
  * Set FAST_SPIBAR Soft Reset Data Register value.
  */