nb/intel/sandybridge: Clarify command timing calculation
Command timing is the absolute value of the most negative `pi_coding`
value across all ranks, or zero if there are no negative values. Use the
MAX() macro to ease proving that `cmd_delay` can never be negative, and
then drop the always-false underflow check.
The variable type for `cmd_delay` still needs to be signed because of
the comparisons with `pi_coding`, which is a signed value. Using an
unsigned type would result in undefined and also undesired behavior.
Change-Id: I714d3cf57d0f62376a1107af63bcd761f952bc3a
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/49320
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
diff --git a/src/northbridge/intel/sandybridge/raminit_common.c b/src/northbridge/intel/sandybridge/raminit_common.c
index f766867..cef0131 100644
--- a/src/northbridge/intel/sandybridge/raminit_common.c
+++ b/src/northbridge/intel/sandybridge/raminit_common.c
@@ -938,16 +938,11 @@
u32 clk_logic_dly = 0;
/*
- * Apply command delay if desired setting is negative. Find the
- * most negative value: 'cmd_delay' will be the absolute value.
+ * Compute command timing as abs() of the most negative PI code
+ * across all ranks. Use zero if none of the values is negative.
*/
FOR_ALL_POPULATED_RANKS {
- if (cmd_delay < -ctrl->timings[channel][slotrank].pi_coding)
- cmd_delay = -ctrl->timings[channel][slotrank].pi_coding;
- }
- if (cmd_delay < 0) {
- printk(BIOS_ERR, "C%d command delay underflow: %d\n", channel, cmd_delay);
- cmd_delay = 0;
+ cmd_delay = MAX(cmd_delay, -ctrl->timings[channel][slotrank].pi_coding);
}
if (cmd_delay > CCC_MAX_PI) {
printk(BIOS_ERR, "C%d command delay overflow: %d\n", channel, cmd_delay);