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nb/intel/pineview: Correct lsbpos(0) and msbpos(0) 

lsbpos and msbpos have incorrect behaviour when given 0.
lsbpos(0) returns 8, and msbpos(0) hangs. The latter is
because the check i >= 0 is always true for an unsigned
integer, causing it to loop indefinitely (this was flagged
by Coverity).

0 doesn't have a lsb or msb position, so we change both
functions to return -1 in this case to indicate an error.
The code already guards against calling these functions
with 0, but we make this more explicit to prevent errors
in the future.

Found-by: Coverity Scan, CID 1347356, 1347386
Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Change-Id: Ic5be50846cc545dcd48593e5ed3fd6068a6104cb
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32054
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
This commit is contained in:
Jacob Garber 2019-03-25 18:20:06 -06:00 committed by Patrick Georgi
parent 0decccb666
commit b70c77691b
1 changed files with 22 additions and 12 deletions
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30
src/northbridge/intel/pineview/raminit.c
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@ -326,18 +326,24 @@ static u32 ddr_reg_to_mhz(u32 speed)
}
#endif
static u8 lsbpos(u8 val) //Forward
// Return the position of the least significant set bit, 0-indexed.
// 0 does not have a lsb, so return -1 for error.
static int lsbpos(u8 val)
{
u8 i;
for (i = 0; (i < 8) && ((val & (1 << i)) == 0); i++);
for (int i = 0; i < 8; i++)
if (val & (1 << i))
return i;
return -1;
}
static u8 msbpos(u8 val) //Reverse
// Return the position of the most significant set bit, 0-indexed.
// 0 does not have a msb, so return -1 for error.
static int msbpos(u8 val)
{
u8 i;
for (i = 7; (i >= 0) && ((val & (1 << i)) == 0); i--);
for (int i = 7; i >= 0; i--)
if (val & (1 << i))
return i;
return -1;
}
static void sdram_detect_smallest_params(struct sysinfo *s)
@ -443,10 +449,14 @@ static void sdram_detect_ram_speed(struct sysinfo *s)
die("No common CAS among dimms\n");
}
// commoncas is nonzero, so these calls will not error
u8 msbp = (u8)msbpos(commoncas);
u8 lsbp = (u8)lsbpos(commoncas);
// Start with fastest common CAS
cas = 0;
highcas = msbpos(commoncas);
lowcas = max(lsbpos(commoncas), 5);
highcas = msbp;
lowcas = max(lsbp, 5);
while (cas == 0 && highcas >= lowcas) {
FOR_EACH_POPULATED_DIMM(s->dimms, i) {
@ -484,8 +494,8 @@ static void sdram_detect_ram_speed(struct sysinfo *s)
die("Timings not supported by MCH\n");
}
cas = 0;
highcas = msbpos(commoncas);
lowcas = lsbpos(commoncas);
highcas = msbp;
lowcas = lsbp;
while (cas == 0 && highcas >= lowcas) {
FOR_EACH_POPULATED_DIMM(s->dimms, i) {
switch (freq) {