[PATCH] devfreq: exynos-bus: workaround dev_pm_opp_set_rate() errors on Exynos5422/5800 SoCs

[k . konieczny]

Commit 4294a779bd8d ("PM / devfreq: exynos-bus: Convert to use
dev_pm_opp_set_rate()") introduced errors:
exynos-bus: new bus device registered: soc:bus_wcore ( 84000 KHz ~ 400000 KHz)
exynos-bus: new bus device registered: soc:bus_noc ( 67000 KHz ~ 100000 KHz)
exynos-bus: new bus device registered: soc:bus_fsys_apb (100000 KHz ~ 200000 
KHz)
...
exynos-bus soc:bus_wcore: dev_pm_opp_set_rate: failed to find current OPP for 
freq 532000000 (-34)
exynos-bus soc:bus_noc: dev_pm_opp_set_rate: failed to find current OPP for 
freq 111000000 (-34)
exynos-bus soc:bus_fsys_apb: dev_pm_opp_set_rate: failed to find current OPP 
for freq 222000000 (-34)

They are caused by incorrect PLL assigned to clock source, which results
in clock rate outside of OPP range. Add workaround for this in
exynos_bus_parse_of() by adjusting clock rate to those present in OPP.

Fixes: 4294a779bd8d ("PM / devfreq: exynos-bus: Convert to use 
dev_pm_opp_set_rate()")
Reported-by: Krzysztof Kozlowski <k...@kernel.org>
Signed-off-by: Kamil Konieczny <k.koniec...@partner.samsung.com>
---
 drivers/devfreq/exynos-bus.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
index c832673273a2..37bd34d5625b 100644
--- a/drivers/devfreq/exynos-bus.c
+++ b/drivers/devfreq/exynos-bus.c
@@ -243,7 +243,7 @@ static int exynos_bus_parse_of(struct device_node *np,
 {
        struct device *dev = bus->dev;
        struct dev_pm_opp *opp;
-       unsigned long rate;
+       unsigned long rate, opp_rate;
        int ret;
 
        /* Get the clock to provide each bus with source clock */
@@ -267,13 +267,21 @@ static int exynos_bus_parse_of(struct device_node *np,
        }
 
        rate = clk_get_rate(bus->clk);
-
-       opp = devfreq_recommended_opp(dev, &rate, 0);
+       opp_rate = rate;
+       opp = devfreq_recommended_opp(dev, &opp_rate, 0);
        if (IS_ERR(opp)) {
                dev_err(dev, "failed to find dev_pm_opp\n");
                ret = PTR_ERR(opp);
                goto err_opp;
        }
+       /*
+        * FIXME: U-boot leaves clock source at incorrect PLL, this results
+        * in clock rate outside defined OPP rate. Work around this bug by
+        * setting clock rate to recommended one.
+        */
+       if (rate > opp_rate)
+               clk_set_rate(bus->clk, opp_rate);
+
        bus->curr_freq = dev_pm_opp_get_freq(opp);
        dev_pm_opp_put(opp);
 
-- 
2.23.0