Hello,
I have a custom i.mx8mm board design with 1GB LPDDR4.
I use kernel branch imx_4.14.98_2.0.0 and everything is working fine. However I tried to switch something more up-to-date : imx_4.14.98_2.3.0
Now the board isn't booting, kernel is loading and CPU freezes.
My investigations leads me to notice that the implementation of drivers/soc/imx/busfreq-imx8mq.c changed. The freeze is caused by the call of arm_smccc_smc(FSL_SIP_DDR_DVFS, 0x11, i, 0, 0, 0, 0, 0, &res); in the probe function.
Removing that call and the associated logic arroung fsp_table solves the issue and kernel is fully booting.
Could someone try to understand what could cause that ?
DDR calibration is done by SPL training and parameters generated by stress tool. Stresstest was successfull too.
origin_noc_rate = clk_get_rate(noc_div);
if (origin_noc_rate == 0) {
WARN_ON(1);
return -EINVAL;
}
/*
* Get the supported frequency, normally the lowest frequency point
* is used for low bus & audio bus mode.
*/
for (i = 0; i < 4; i++) {
arm_smccc_smc(FSL_SIP_DDR_DVFS, 0x11, i, 0, 0, 0, 0, 0, &res);
err = res.a0;
if (err < 0)
return -EINVAL;
fsp_table[i] = res.a0;
}
/* get the lowest fsp index */
for (i = 0; i < 4; i++)
if (fsp_table[i] == 0)
break;
low_bus_mode_fsp_index = i - 1;
/*
* if lowest fsp data rate higher than 666mts, then no dll off mode or
* bypass mode support.
*/
if (fsp_table[low_bus_mode_fsp_index] >= DLL_ON_DRATE)
bypass_support = false;
