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

From: Chanwoo Choi
Date: Wed Dec 04 2019 - 21:42:43 EST

Hi Kamil,

On 11/14/19 4:38 PM, Chanwoo Choi wrote:
> Hi Kamil,
>
> On 11/14/19 3:07 PM, Chanwoo Choi wrote:
>> Hi Kamil,
>>
>> On 11/14/19 12:12 AM, Kamil Konieczny wrote:
>>> Hi Chanwoo,
>>>
>>> On 14.10.2019 08:46, Chanwoo Choi wrote:
>>>> Hi Marek,
>>>>
>>>> On 19. 10. 11. ìí 8:33, Marek Szyprowski wrote:
>>>>> Hi Chanwoo,
>>>>>
>>>>> On 10.10.2019 04:50, Chanwoo Choi wrote:
>>>>>> On 2019ë 10ì 08ì 22:49, k.konieczny@xxxxxxxxxxxxxxxxxxx wrote:
>>>>>>> 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.
>>>>>> If the clock caused this issue, you can set the initial clock on DeviceTree
>>>>>> with assigned-clock-* properties. Because the probe time of clock driver
>>>>>> is early than the any device drivers.
>>>>>>
>>>>>> It is not proper to fix the clock issue on other device driver.
>>>>>> I think you can fix it by using the supported clock properties.
>>>>>
>>>>> This issue is about something completely different. The OPPs defined in
>>>>> DT cannot be applied, because it is not possible to derive the needed
>>>>> clock rate from the bootloader-configured clock topology (mainly due to
>>>>> lack of common divisor values for some of the parent clocks). Some time
>>>>> ago Lukasz tried initially to redefine this clock topology using
>>>>> assigned-clock-rates/parents properties (see
>>>>> https://protect2.fireeye.com/url?k=4b80c0304459bc8e.4b814b7f-f87f1e1aee1a85c0&u=https://lkml.org/lkml/2019/7/15/276), but it has limitations and some
>>>>> such changes has to be done in bootloader. Until this is resolved,
>>>>> devfreq simply cannot set some of the defined OPPs.
>>>>
>>>> As you mentioned, the wrong setting in bootloader cause the this issue.
>>>> So, this patch change the rate on exynos-bus.c in order to fix
>>>> the issue with workaround style.
>>>>
>>>> But, also, it can be fixed by initializing the clock rate on DT
>>>> although it is not fundamental solution as you mentioned.
>>>>
>>>> If above two method are workaround way, I think that set the clock
>>>> rate in DT is proper. The role of 'assigned-clock-*' properties
>>>> is for this case in order to set the initial frequency on probe time.
>>>
>>> I can add 'assigned-clock-*' to DT, but the issue is caused in opp points,
>>> so the warning from exynos-bus will still be there.
>>>
>>> Before this fix, devfreq will issue warning and then change clock to max
>>> frequency within opp range. This fix mask warning, and as Marek and
>>> Lukasz Luba wrotes, the proper fix will be to make changes in u-boot
>>> (and connect proper PLLs to IPs).
>>
>> PLL could be changed by clock device driver in the linux kernel.
>> If you don't add the supported frequency into PLL frequency table
>> of clock device driver, will fail to change the wanted frequency
>> on the linux kernel. It means that it is not fixed by only touching
>> the bootloader.
>>
>> As you commented, the wrong opp points which are specified on dt
>> cause this issue. Usually, have to initialize the clock rate on dt
>> by using 'assigned-clocks-*' property and then use the clock
>> with the preferable clock rate. I think that we have to fix
>> the fundamental problem.
>>
>> Without bootloader problem, you can fix it by initializing
>> the clock on dt with 'assigned-clocks-*' property.
>>
>> As I knew that it is correct way and I always tried to do this method
>> for resolving the similar clock issue.
>>
>> Lastly, I think that my opinion is more simple and correct.
>> It could give the more correct information to linux kernel user
>> which refer to the device tree file.
>>
>> 1. Your suggestion
>> a. Add opp-table with unsupported frequency on dt
>> b. Try to change the clock rate on exynos-bus.c by using unsupported frequency from opp-table
>> c. If failed, retry to change the clock rate on exynos-bus.c
>>
>> 2. My opinion
>> a. Initialize the PLL or any clock by using assigned-clock-* property on dt
>> and add opp-table with supported frequency on dt
>> b. Try to change the clock rate on exynos-bus.c by using supported frequency from opp-table
>>
>
> Just I tried to add 'assigned-clock-rates' property to initialize
> the clock rate of some bus node as following on odroid-xu3 board:
>
> diff --git a/arch/arm/boot/dts/exynos5422-odroid-core.dtsi b/arch/arm/boot/dts/exynos5422-odroid-core.dtsi
> index 829147e320e0..9a237af5436a 100644
> --- a/arch/arm/boot/dts/exynos5422-odroid-core.dtsi
> +++ b/arch/arm/boot/dts/exynos5422-odroid-core.dtsi
> @@ -42,6 +42,8 @@
> };
>
> &bus_wcore {
> + assigned-clocks = <&clock CLK_DOUT_ACLK400_WCORE>;
> + assigned-clock-rates = <400000000>;
> devfreq-events = <&nocp_mem0_0>, <&nocp_mem0_1>,
> <&nocp_mem1_0>, <&nocp_mem1_1>;
> vdd-supply = <&buck3_reg>;
> @@ -50,11 +52,15 @@
> };
>
> &bus_noc {
> + assigned-clocks = <&clock CLK_DOUT_ACLK100_NOC>;
> + assigned-clock-rates = <100000000>;
> devfreq = <&bus_wcore>;
> status = "okay";
> };
>
> &bus_fsys_apb {
> + assigned-clocks = <&clock CLK_DOUT_PCLK200_FSYS>;
> + assigned-clock-rates = <200000000>;
> devfreq = <&bus_wcore>;
> status = "okay";
> };
> @@ -120,6 +126,8 @@
> };
>
> &bus_mscl {
> + assigned-clocks = <&clock CLK_DOUT_ACLK400_MSCL>;
> + assigned-clock-rates = <400000000>;
> devfreq = <&bus_wcore>;
> status = "okay";
> };
>
>
> In result,
> [Before on v5.4-rc6, failed to set the rate by dev_pm_opp_set_rate()]
> [ 4.855811] exynos-bus: new bus device registered: soc:bus_wcore ( 84000 KHz ~ 400000 KHz)
> [ 4.863374] exynos-bus: new bus device registered: soc:bus_noc ( 67000 KHz ~ 100000 KHz)
> [ 4.871240] exynos-bus: new bus device registered: soc:bus_fsys_apb (100000 KHz ~ 200000 KHz)
> [ 4.879509] exynos-bus: new bus device registered: soc:bus_fsys (100000 KHz ~ 200000 KHz)
> [ 4.887957] exynos-bus: new bus device registered: soc:bus_fsys2 ( 75000 KHz ~ 150000 KHz)
> [ 4.896361] exynos-bus: new bus device registered: soc:bus_mfc ( 96000 KHz ~ 333000 KHz)
> [ 4.904330] exynos-bus: new bus device registered: soc:bus_gen ( 89000 KHz ~ 267000 KHz)
> [ 4.911802] exynos-bus soc:bus_wcore: dev_pm_opp_set_rate: failed to find current OPP for freq 532000000 (-34)
> [ 4.912710] exynos-bus: new bus device registered: soc:bus_peri ( 67000 KHz ~ 67000 KHz)
> [ 4.924655] exynos-bus soc:bus_noc: dev_pm_opp_set_rate: failed to find current OPP for freq 111000000 (-34)
> [ 4.932125] exynos-bus: new bus device registered: soc:bus_g2d ( 84000 KHz ~ 333000 KHz)
> [ 4.939607] exynos-bus soc:bus_fsys_apb: dev_pm_opp_set_rate: failed to find current OPP for freq 222000000 (-34)
> [ 4.949758] exynos-bus: new bus device registered: soc:bus_g2d_acp ( 67000 KHz ~ 267000 KHz)
> [ 4.966991] exynos-bus: new bus device registered: soc:bus_jpeg ( 75000 KHz ~ 300000 KHz)
> [ 4.975136] exynos-bus: new bus device registered: soc:bus_jpeg_apb ( 84000 KHz ~ 167000 KHz)
> [ 4.983452] exynos-bus: new bus device registered: soc:bus_disp1_fimd (120000 KHz ~ 200000 KHz)
> [ 4.992218] exynos-bus: new bus device registered: soc:bus_disp1 (120000 KHz ~ 300000 KHz)
> [ 5.000483] exynos-bus: new bus device registered: soc:bus_gscl_scaler (150000 KHz ~ 300000 KHz)
> [ 5.009331] exynos-bus: new bus device registered: soc:bus_mscl ( 84000 KHz ~ 400000 KHz)
> [ 5.020207] exynos-bus soc:bus_mscl: dev_pm_opp_set_rate: failed to find current OPP for freq 666000000 (-34)
>
> [After applied the 'assigned-clock-*' patch on v5.4-rc6]
> [ 4.840571] exynos-bus: new bus device registered: soc:bus_wcore ( 84000 KHz ~ 400000 KHz)
> [ 4.848099] exynos-bus: new bus device registered: soc:bus_noc ( 67000 KHz ~ 100000 KHz)
> [ 4.856016] exynos-bus: new bus device registered: soc:bus_fsys_apb (100000 KHz ~ 200000 KHz)
> [ 4.864307] exynos-bus: new bus device registered: soc:bus_fsys (100000 KHz ~ 200000 KHz)
> [ 4.872723] exynos-bus: new bus device registered: soc:bus_fsys2 ( 75000 KHz ~ 150000 KHz)
> [ 4.881124] exynos-bus: new bus device registered: soc:bus_mfc ( 96000 KHz ~ 333000 KHz)
> [ 4.889147] exynos-bus: new bus device registered: soc:bus_gen ( 89000 KHz ~ 267000 KHz)
> [ 4.896867] exynos-bus: new bus device registered: soc:bus_peri ( 67000 KHz ~ 67000 KHz)
> [ 4.907430] exynos-bus: new bus device registered: soc:bus_g2d ( 84000 KHz ~ 333000 KHz)
> [ 4.914797] exynos-bus: new bus device registered: soc:bus_g2d_acp ( 67000 KHz ~ 267000 KHz)
> [ 4.923205] exynos-bus: new bus device registered: soc:bus_jpeg ( 75000 KHz ~ 300000 KHz)
> [ 4.931352] exynos-bus: new bus device registered: soc:bus_jpeg_apb ( 84000 KHz ~ 167000 KHz)
> [ 4.939658] exynos-bus: new bus device registered: soc:bus_disp1_fimd (120000 KHz ~ 200000 KHz)
> [ 4.948401] exynos-bus: new bus device registered: soc:bus_disp1 (120000 KHz ~ 300000 KHz)
> [ 4.956650] exynos-bus: new bus device registered: soc:bus_gscl_scaler (150000 KHz ~ 300000 KHz)
> [ 4.965573] exynos-bus: new bus device registered: soc:bus_mscl ( 84000 KHz ~ 400000 KHz)
>

Actually, I don't want to leave this problem on mainline.
We have to need to fix the fail of exynos-bus registration for kernel booting.
Please reply your opinion or send the fix-up patch as I commented above.

>
>>>
>>> Second solution would be to write down new OPP points with currently used
>>> frequencies, and with max one for 532 MHz.
>>>
>>>> I think that the previous patch[1] of Kamil Konieczny is missing
>>>> the patches which initialize the clock rate on DT file.
>>>> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4294a779bd8dff6c65e7e85ffe7a1ea236e92a68
>>>>
>>>>>
>>>>> This issue was there from the beginning, recent Kamil's patch only
>>>>> revealed it. In fact it was even worse - devfreq and common clock
>>>>> framework silently set lower clock than the given OPP defined.
>>>>>
>>>>>>> Fixes: 4294a779bd8d ("PM / devfreq: exynos-bus: Convert to use dev_pm_opp_set_rate()")
>>>>>>> Reported-by: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
>>>>>>> Signed-off-by: Kamil Konieczny <k.konieczny@xxxxxxxxxxxxxxxxxxx>
>>>>>>> ---
>>>>>>> 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);
>>>>>>>
>>>>>>>
>>>>>>
>>>>> Best regards
>>>>>
>>>>
>>>>
>>>
>>
>>
>
>


--
Best Regards,
Chanwoo Choi
Samsung Electronics