xfnw/plan9fox
1
0
Fork 0
Code Issues Pull requests Projects Releases Wiki Activity

bcm64: fix wrong prescaler for generic timer on rpi4

Browse source 
the raspberry pi 4 uses 54 instead of 19.2 MHz crystal.
detect which frequency is used by reading OTP bootmode
register:

https://www.raspberrypi.org/documentation/hardware/raspberrypi/otpbits.md

Bit 1: sets the oscillator frequency to 19.2MHz
This commit is contained in:
cinap_lenrek 2019-07-27 17:59:25 +02:00
parent 834f670349
commit ea2a5a33ca
2 changed files with 12 additions and 2 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
sys/src/9/bcm64/clock.c
View file

@ -121,14 +121,23 @@ clockinit(void)
syswr(CNTP_TVAL_EL0, ~0UL);
if(m->machno == 0){
int oscfreq;
syswr(CNTP_CTL_EL0, Imask);
*(u32int*)(ARMLOCAL + GPUirqroute) = 0;
/* input clock is 19.2Mhz crystal */
/* bit 1 from OTP bootmode register determines OSC frequency */
if(*((u32int*)(VIRTIO+0x20f000)) & (1<<1))
oscfreq = 19200000;
else
oscfreq = 54000000;
/* input clock to OSC */
*(u32int*)(ARMLOCAL + Localctl) = 0;
/* divide by (2^31/Prescaler) */
*(u32int*)(ARMLOCAL + Prescaler) = (((uvlong)SystimerFreq<<31)/19200000)&~1UL;
*(u32int*)(ARMLOCAL + Prescaler) = (((uvlong)SystimerFreq<<31)/oscfreq)&~1UL;
} else {
syswr(CNTP_CTL_EL0, Enable);
intrenable(IRQcntpns, localclockintr, nil, BUSUNKNOWN, "clock");

1
sys/src/9/bcm64/sysreg.h
View file

@ -31,6 +31,7 @@
#define PMCCNTR_EL0 SYSREG(3,3,9,13,0)
#define PMUSERENR_EL0 SYSREG(3,3,9,14,0)
#define CNTPCT_EL0 SYSREG(3,3,14,0,1)
#define CNTP_TVAL_EL0 SYSREG(3,3,14,2,0)
#define CNTP_CTL_EL0 SYSREG(3,3,14,2,1)
#define CNTP_CVAL_EL0 SYSREG(3,3,14,2,2)