> Bootloaders should in theory setup a frequency which is enabled in
> OPP table. However, there can be mismatches, and we should try
> both going lower in addition to the going higher to find
> a match if bootloader boots up at a OPP than the kernel thinks it
> should be allowed. We also sequence the frequency and voltage settings
> properly.
>
> Reported-by: Colin Cross <ccr...@google.com>
> Signed-off-by: Nishanth Menon <n...@ti.com>
> ---
> PS: Apologies on the spam.. for some reason 10/10 never appeared in
> http://marc.info/?l=linux-omap&r=2&b=201106&w=2 - grumble grumble :(
>
> arch/arm/mach-omap2/pm.c | 55 ++++++++++++++++++++++++++++++++++++---------
> 1 files changed, 44 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/mach-omap2/pm.c b/arch/arm/mach-omap2/pm.c
> index 7355347..ce7554b 100644
> --- a/arch/arm/mach-omap2/pm.c
> +++ b/arch/arm/mach-omap2/pm.c
> @@ -174,7 +174,9 @@ static int __init omap2_set_init_voltage(char *vdd_name,
> ch ar *clk_name,
> struct voltagedomain *voltdm;
> struct clk *clk;
> struct opp *opp;
> - unsigned long freq, bootup_volt;
> + unsigned long freq_cur, freq_valid, bootup_volt;
> + int raise_freq_idx, i;
> + int ret = -EINVAL;
>
> if (!vdd_name || !clk_name || !dev) {
> printk(KERN_ERR "%s: Invalid parameters!\n", __func__);
> @@ -195,16 +197,20 @@ static int __init omap2_set_init_voltage(char
> *vdd_name, char *clk_name,
> goto exit;
> }
>
> - freq = clk->rate;
> - clk_put(clk);
> + freq_cur = clk->rate;
> + freq_valid = freq_cur;
>
> rcu_read_lock();
> - opp = opp_find_freq_ceil(dev, &freq);
> + opp = opp_find_freq_ceil(dev, &freq_valid);
> if (IS_ERR(opp)) {
> - rcu_read_unlock();
> - printk(KERN_ERR "%s: unable to find boot up OPP for vdd_%s\n",
> - __func__, vdd_name);
> - goto exit;
> + opp = opp_find_freq_floor(dev, &freq_valid);
> + if (IS_ERR(opp)) {
> + rcu_read_unlock();
> + pr_err("%s: no boot OPP match for %ld on vdd_%s\n",
> + __func__, freq_cur, vdd_name);
> + ret = -ENOENT;
> + goto exit_ck;
> + }
> }
>
> bootup_volt = opp_get_voltage(opp);
> @@ -212,11 +218,38 @@ static int __init omap2_set_init_voltage(char
> *vdd_name, char *clk_name,
> if (!bootup_volt) {
> printk(KERN_ERR "%s: unable to find voltage corresponding"
> "to the bootup OPP for vdd_%s\n", __func__, vdd_name);
> - goto exit;
> + ret = -ENOENT;
> + goto exit_ck;
> }
>
> - voltdm_scale(voltdm, bootup_volt);
> - return 0;
> + /*
> + * Frequency and Voltage have to be sequenced: if we move from
> + * a lower frequency to higher frequency, raise voltage, followed by
> + * frequency, and vice versa. we assume that the voltage at boot
> + * is the required voltage for the frequency it was set for.
> + */
> + raise_freq_idx = freq_cur < freq_valid;
> + for (i = 0; i < 2; i++) {
> + if (i == raise_freq_idx)
> + ret = clk_set_rate(clk, freq_valid);
> + else
> + ret = voltdm_scale(voltdm, bootup_volt);
> + if (ret < 0) {
> + pr_err("%s: unable to set %s-%s(f=%ld v=%ld)on vdd%s\n",
> + __func__,
> + (i == raise_freq_idx) ? "clk" : "voltage",
> + (i == raise_freq_idx) ? clk_name : vdd_name,
> + freq_valid, bootup_volt, vdd_name);
> + goto exit_ck;
> + }
> + }
This is way too complicated. Writing out what you mean is much more
readable, and not many more LOC:
if (freq_cur < freq_valid) {
ret = voltdm_scale(voltdm, bootup_volt);
if (ret) {
pr_err("%s: unable to set voltage-%s(f=%ld v=%ld)on vdd%s\n",
vdd_name, freq_valid, bootup_volt, vdd_name);
goto exit_ck;
}
}
ret = clk_set_rate(clk, freq_valid);
if (ret) {
pr_err("%s: unable to set clk-%s(f=%ld v=%ld)on vdd%s\n",
clk_name, freq_valid, bootup_volt, vdd_name);
goto exit_ck;
}
if (freq_cur > freq_valid) {
ret = voltdm_scale(voltdm, bootup_volt);
if (ret) {
pr_err("%s: unable to set voltage-%s(f=%ld v=%ld)on vdd%s\n",
vdd_name, freq_valid, bootup_volt, vdd_name);
goto exit_ck;
}
}
> +
> + ret = 0;
> +exit_ck:
> + clk_put(clk);
> +
> + if (!ret)
> + return 0;
>
> exit:
> printk(KERN_ERR "%s: Unable to put vdd_%s to its init voltage\n\n",
> --
> 1.7.1
>
> --
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