writeprotect.c: skip unnecessary writes
* Don't write register because of RO and OTP bits.
* Skip the write of RW bits if register state wouldn't change by it.
Change-Id: I81d2d3fc0a103ee00ced78838d77fe33a9d3056a
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Original-Reviewed-on: https://review.coreboot.org/c/flashrom/+/66754
Original-Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Original-Reviewed-by: Nikolai Artemiev <nartemiev@google.com>
Reviewed-on: https://review.coreboot.org/c/flashrom-stable/+/71004
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/writeprotect.c b/writeprotect.c
index 11219e2..48c5ae6 100644
--- a/writeprotect.c
+++ b/writeprotect.c
@@ -90,12 +90,16 @@
/** Helper function for write_wp_bits(). */
static void set_reg_bit(
- uint8_t *reg_values, uint8_t *write_masks,
+ uint8_t *reg_values, uint8_t *bit_masks, uint8_t *write_masks,
struct reg_bit_info bit, uint8_t value)
{
if (bit.reg != INVALID_REG) {
reg_values[bit.reg] |= value << bit.bit_index;
- write_masks[bit.reg] |= 1 << bit.bit_index;
+ bit_masks[bit.reg] |= 1 << bit.bit_index;
+
+ /* Avoid RO and OTP bits causing a register update */
+ if (bit.writability == RW)
+ write_masks[bit.reg] |= 1 << bit.bit_index;
}
}
@@ -106,22 +110,23 @@
enum flash_reg reg;
const struct reg_bit_map *reg_bits = &flash->chip->reg_bits;
- /* Convert wp_bits to register values and write masks */
+ /* Convert wp_bits to register values and masks */
uint8_t reg_values[MAX_REGISTERS] = {0};
- uint8_t write_masks[MAX_REGISTERS] = {0};
+ uint8_t bit_masks[MAX_REGISTERS] = {0}; /* masks of valid bits */
+ uint8_t write_masks[MAX_REGISTERS] = {0}; /* masks of written bits */
for (i = 0; i < bits.bp_bit_count; i++)
- set_reg_bit(reg_values, write_masks, reg_bits->bp[i], bits.bp[i]);
+ set_reg_bit(reg_values, bit_masks, write_masks, reg_bits->bp[i], bits.bp[i]);
- set_reg_bit(reg_values, write_masks, reg_bits->tb, bits.tb);
- set_reg_bit(reg_values, write_masks, reg_bits->sec, bits.sec);
- set_reg_bit(reg_values, write_masks, reg_bits->cmp, bits.cmp);
- set_reg_bit(reg_values, write_masks, reg_bits->srp, bits.srp);
- set_reg_bit(reg_values, write_masks, reg_bits->srl, bits.srl);
+ set_reg_bit(reg_values, bit_masks, write_masks, reg_bits->tb, bits.tb);
+ set_reg_bit(reg_values, bit_masks, write_masks, reg_bits->sec, bits.sec);
+ set_reg_bit(reg_values, bit_masks, write_masks, reg_bits->cmp, bits.cmp);
+ set_reg_bit(reg_values, bit_masks, write_masks, reg_bits->srp, bits.srp);
+ set_reg_bit(reg_values, bit_masks, write_masks, reg_bits->srl, bits.srl);
/* Note: always setting WPS bit to zero until its fully supported. */
- set_reg_bit(reg_values, write_masks, reg_bits->wps, 0);
+ set_reg_bit(reg_values, bit_masks, write_masks, reg_bits->wps, 0);
- /* Write each register */
+ /* Write each register whose value was updated */
for (reg = STATUS1; reg < MAX_REGISTERS; reg++) {
if (!write_masks[reg])
continue;
@@ -130,16 +135,22 @@
if (spi_read_register(flash, reg, &value))
return FLASHROM_WP_ERR_READ_FAILED;
- value = (value & ~write_masks[reg]) | (reg_values[reg] & write_masks[reg]);
+ /* Skip unnecessary register writes */
+ uint8_t actual = value & write_masks[reg];
+ uint8_t expected = reg_values[reg] & write_masks[reg];
+ if (actual == expected)
+ continue;
+
+ value = (value & ~write_masks[reg]) | expected;
if (spi_write_register(flash, reg, value))
return FLASHROM_WP_ERR_WRITE_FAILED;
}
enum flashrom_wp_result ret = FLASHROM_WP_OK;
- /* Verify each register */
+ /* Verify each register even if write to it was skipped */
for (reg = STATUS1; reg < MAX_REGISTERS; reg++) {
- if (!write_masks[reg])
+ if (!bit_masks[reg])
continue;
uint8_t value;
@@ -147,8 +158,8 @@
return FLASHROM_WP_ERR_READ_FAILED;
msg_cdbg2("%s: wp_verify reg:%u value:0x%x\n", __func__, reg, value);
- uint8_t actual = value & write_masks[reg];
- uint8_t expected = reg_values[reg] & write_masks[reg];
+ uint8_t actual = value & bit_masks[reg];
+ uint8_t expected = reg_values[reg] & bit_masks[reg];
if (actual != expected) {
msg_cdbg("%s: wp_verify failed: reg:%u actual:0x%x expected:0x%x\n",