skylake: Add function to set PRR for protecting flash

Add a function similar to broadwell to set the PRR for a region of
flash and protect it from writes.  This is used to secure the MRC
cache region if the SPI is write protected.

BUG=chrome-os-partner:54003
BRANCH=glados
TEST=boot on chell, verify PRR register is set and that the
MRC cache region cannot be written if the SPI is write protected.

Change-Id: I925ec9ce186f7adac327bca9c96255325b7f54ec
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Original-Commit-Id: abb6f645f5ceef3f52bb7afd2632212ea916ff8d
Original-Change-Id: I2f90556a217b35b7c93645e41a1fcfe8070c53da
Original-Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/349274
Original-Reviewed-by: Shawn N <shawnn@chromium.org>
Original-Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Original-Tested-by: Shawn N <shawnn@chromium.org>
Reviewed-on: https://review.coreboot.org/15102
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-by: Leroy P Leahy <leroy.p.leahy@intel.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

1 files changed, 37 insertions, 0 deletions

diff --git a/src/soc/intel/skylake/flash_controller.c b/src/soc/intel/skylake/flash_controller.c
index 0af0484082..3507b471cc 100644
--- a/src/soc/intel/skylake/flash_controller.c
+++ b/src/soc/intel/skylake/flash_controller.c
@@ -386,6 +386,43 @@ struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs)
 	return slave;
 }
 
+int spi_flash_protect(u32 start, u32 size)
+{
+	pch_spi_regs *spi_bar = get_spi_bar();
+	u32 end = start + size - 1;
+	u32 reg;
+	int prr;
+
+	if (!spi_bar)
+		return -1;
+
+	/* Find first empty PRR */
+	for (prr = 0; prr < SPI_PRR_MAX; prr++) {
+		reg = read32(&spi_bar->pr[prr]);
+		if (reg == 0)
+			break;
+	}
+	if (prr >= SPI_PRR_MAX) {
+		printk(BIOS_ERR, "ERROR: No SPI PRR free!\n");
+		return -1;
+	}
+
+	/* Set protected range base and limit */
+	reg = SPI_PRR(start, end) | SPI_PRR_WPE;
+
+	/* Set the PRR register and verify it is protected */
+	write32(&spi_bar->pr[prr], reg);
+	reg = read32(&spi_bar->pr[prr]);
+	if (!(reg & SPI_PRR_WPE)) {
+		printk(BIOS_ERR, "ERROR: Unable to set SPI PRR %d\n", prr);
+		return -1;
+	}
+
+	printk(BIOS_INFO, "%s: PRR %d is enabled for range 0x%08x-0x%08x\n",
+	       __func__, prr, start, end);
+	return 0;
+}
+
 #if ENV_RAMSTAGE
 /*
  * spi_init() needs run unconditionally in every boot (including resume) to