Re: [PATCH v10 5/8] soc/tegra: pmc: Implement dev_get_performance_state() callback

Dmitry Osipenko
2021-09-01T06:57:43Z

01.09.2021 09:10, Viresh Kumar пишет:
> On 31-08-21, 16:54, Dmitry Osipenko wrote:
>> +static int
>> +tegra_pmc_pd_dev_get_performance_state(struct generic_pm_domain *genpd,
>> + struct device *dev)
>> +{
>> + struct opp_table *hw_opp_table, *clk_opp_table;
>> + struct dev_pm_opp *opp;
>> + u32 hw_version;
>> + int ret;
>> +
>> + /*
>> + * The EMC devices are a special case because we have a protection
>> + * from non-EMC drivers getting clock handle before EMC driver is
>> + * fully initialized. The goal of the protection is to prevent
>> + * devfreq driver from getting failures if it will try to change
>> + * EMC clock rate until clock is fully initialized. The EMC drivers
>> + * will initialize the performance state by themselves.
>> + *
>> + * Display controller also is a special case because only controller
>> + * driver could get the clock rate based on configuration of internal
>> + * divider.
>> + *
>> + * Clock driver uses its own state syncing.
>> + */
>> + if (of_device_compatible_match(dev->of_node, tegra_pd_no_perf_compats))
>> + return 0;
>> +
>> + if (of_machine_is_compatible("nvidia,tegra20"))
>> + hw_version = BIT(tegra_sku_info.soc_process_id);
>> + else
>> + hw_version = BIT(tegra_sku_info.soc_speedo_id);
>> +
>> + hw_opp_table = dev_pm_opp_set_supported_hw(dev, &hw_version, 1);
>> + if (IS_ERR(hw_opp_table)) {
>> + dev_err(dev, "failed to set OPP supported HW: %pe\n",
>> + hw_opp_table);
>> + return PTR_ERR(hw_opp_table);
>> + }
>> +
>> + /*
>> + * Older device-trees don't have OPPs, meanwhile drivers use
>> + * dev_pm_opp_set_rate() and it requires OPP table to be set
>> + * up using dev_pm_opp_set_clkname().
>> + *
>> + * The devm_tegra_core_dev_init_opp_table() is a common helper
>> + * that sets up OPP table for Tegra drivers and it sets the clk
>> + * for compatibility with older device-tress. GR3D driver uses that
>> + * helper, it also uses devm_pm_opp_attach_genpd() to manually attach
>> + * power domains, which now holds the reference to OPP table that
>> + * already has clk set up implicitly by OPP core for a newly created
>> + * table using dev_pm_opp_of_add_table() invoked below.
>> + *
>> + * Hence we need to explicitly set/put the clk, otherwise
>> + * further dev_pm_opp_set_clkname() will fail with -EBUSY.
>> + */
>> + clk_opp_table = dev_pm_opp_set_clkname(dev, NULL);
>> + if (IS_ERR(clk_opp_table)) {
>> + dev_err(dev, "failed to set OPP clk: %pe\n", clk_opp_table);
>> + ret = PTR_ERR(clk_opp_table);
>> + goto put_hw;
>> + }
>> +
>> + ret = dev_pm_opp_of_add_table(dev);
>> + if (ret) {
>> + dev_err(dev, "failed to add OPP table: %d\n", ret);
>> + goto put_clk;
>> + }
>> +
>> + opp = dev_pm_opp_get_current(dev);
>> + if (IS_ERR(opp)) {
>> + dev_err(dev, "failed to get current OPP: %pe\n", opp);
>> + ret = PTR_ERR(opp);
>> + } else {
>> + ret = dev_pm_opp_get_required_pstate(opp, 0);
>> + dev_pm_opp_put(opp);
>> + }
>> +
>> + dev_pm_opp_of_remove_table(dev);
>> +put_clk:
>> + dev_pm_opp_put_clkname(clk_opp_table);
>> +put_hw:
>> + dev_pm_opp_put_supported_hw(hw_opp_table);
>
> So you create the OPP table and just after that you remove it ? Just
> to get the current OPP and pstate ? This doesn't look okay.
>
> Moreover, this routine must be implemented with the expectation that
> the genpd core can call it anytime it wants, not just at the
> beginning. And so if the table is already setup by someone else then,
> then this all will just fail.

This is not doable using the current OPP API, it doesn't allow to re-use initialized OPP table. The current limitation is okay because genpd core doesn't call routine anytime.

> I did have a look at the comment you added above regarding
> devm_tegra_core_dev_init_opp_table(), but I am not sure of the series
> of events right now. For me, the OPP table should just be added once
> and for ever. You shouldn't remove and add it again. That is bound to
> break somewhere later.

I see that the comment about devm_tegra_core_dev_init_opp_table() is outdated now, will update it. There was a refcounting bug in v9 where I accidentally used devm_pm_opp_of_add_table instead of dev_, still it fails similarly, but in a different place now.

> Can you give the sequence in which the whole thing works out with
> respect to the OPP core? who calls
> devm_tegra_core_dev_init_opp_table() and when, and when exactly will
> this routine get called, etc ?
>

gr3d_probe(struct platform_device *pdev)
{
gr3d_init_power(dev)
{
static const char * const opp_genpd_names[] = { "3d0", "3d1", NULL };

devm_pm_opp_attach_genpd(dev, opp_genpd_names)
{
dev_pm_opp_attach_genpd(dev, names, virt_devs)
{
// takes and holds table reference
opp_table = _add_opp_table(dev, false);

while (*name) {
// first attachment succeeds,
// second fails with "tegra-gr3d 54180000.gr3d: failed to set OPP clk: -EBUSY"
dev_pm_domain_attach_by_name(dev, *name)
{
tegra_pmc_pd_dev_get_performance_state(dev)
{
dev_pm_opp_set_clkname(dev, NULL);
dev_pm_opp_of_add_table(dev);
opp = dev_pm_opp_get_current(dev);
dev_pm_opp_of_remove_table(dev);
dev_pm_opp_put_clkname(opp_table);
...
}
// opp_table->clk = ERR_PTR(-EINVAL) after the first attachment
}
}
}
}
}

devm_tegra_core_dev_init_opp_table_simple(&pdev->dev);

return 0;
}

WARNING: CPU: 3 PID: 7 at drivers/opp/core.c:2151 dev_pm_opp_set_clkname+0x97/0xb8
Modules linked in:
CPU: 3 PID: 7 Comm: kworker/u8:0 Tainted: G W 5.14.0-next-20210831-00177-g6850c69f8c92-dirty #9371
Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
Workqueue: events_unbound deferred_probe_work_func
[<c010cc91>] (unwind_backtrace) from [<c0108d35>] (show_stack+0x11/0x14)
[<c0108d35>] (show_stack) from [<c0a6e25d>] (dump_stack_lvl+0x2b/0x34)
[<c0a6e25d>] (dump_stack_lvl) from [<c011fc7f>] (__warn+0xbb/0x100)
[<c011fc7f>] (__warn) from [<c0a6b783>] (warn_slowpath_fmt+0x4b/0x80)
[<c0a6b783>] (warn_slowpath_fmt) from [<c0742613>] (dev_pm_opp_set_clkname+0x97/0xb8)
[<c0742613>] (dev_pm_opp_set_clkname) from [<c0509815>] (tegra_pmc_pd_dev_get_performance_state+0x85/0x120)
[<c0509815>] (tegra_pmc_pd_dev_get_performance_state) from [<c05cd3db>] (__genpd_dev_pm_attach+0xe7/0x218)
[<c05cd3db>] (__genpd_dev_pm_attach) from [<c05cd5d3>] (genpd_dev_pm_attach_by_id+0x8b/0xec)
[<c05cd5d3>] (genpd_dev_pm_attach_by_id) from [<c074287f>] (dev_pm_opp_attach_genpd+0x97/0x11c)
[<c074287f>] (dev_pm_opp_attach_genpd) from [<c0742913>] (devm_pm_opp_attach_genpd+0xf/0x6c)
[<c0742913>] (devm_pm_opp_attach_genpd) from [<c05ac7a5>] (gr3d_probe+0x245/0x348)
[<c05ac7a5>] (gr3d_probe) from [<c05bc003>] (platform_probe+0x43/0x84)
[<c05bc003>] (platform_probe) from [<c05ba569>] (really_probe.part.0+0x69/0x200)
[<c05ba569>] (really_probe.part.0) from [<c05ba773>] (__driver_probe_device+0x73/0xd4)
[<c05ba773>] (__driver_probe_device) from [<c05ba809>] (driver_probe_device+0x35/0xd0)
[<c05ba809>] (driver_probe_device) from [<c05bac11>] (__device_attach_driver+0x75/0x98)
[<c05bac11>] (__device_attach_driver) from [<c05b9005>] (bus_for_each_drv+0x51/0x7c)
[<c05b9005>] (bus_for_each_drv) from [<c05ba9f7>] (__device_attach+0x8b/0x104)
[<c05ba9f7>] (__device_attach) from [<c05b9b1b>] (bus_probe_device+0x5b/0x60)
[<c05b9b1b>] (bus_probe_device) from [<c05b7707>] (device_add+0x293/0x65c)
[<c05b7707>] (device_add) from [<c07798b7>] (of_platform_device_create_pdata+0x63/0x88)
[<c07798b7>] (of_platform_device_create_pdata) from [<c07799e5>] (of_platform_bus_create+0xfd/0x26c)
[<c07799e5>] (of_platform_bus_create) from [<c0779c2d>] (of_platform_populate+0x45/0x84)
[<c0779c2d>] (of_platform_populate) from [<c0779cc5>] (devm_of_platform_populate+0x41/0x6c)
[<c0779cc5>] (devm_of_platform_populate) from [<c054aa65>] (host1x_probe+0x1e9/0x2c8)
[<c054aa65>] (host1x_probe) from [<c05bc003>] (platform_probe+0x43/0x84)
[<c05bc003>] (platform_probe) from [<c05ba569>] (really_probe.part.0+0x69/0x200)
[<c05ba569>] (really_probe.part.0) from [<c05ba773>] (__driver_probe_device+0x73/0xd4)
[<c05ba773>] (__driver_probe_device) from [<c05ba809>] (driver_probe_device+0x35/0xd0)
[<c05ba809>] (driver_probe_device) from [<c05bac11>] (__device_attach_driver+0x75/0x98)
[<c05bac11>] (__device_attach_driver) from [<c05b9005>] (bus_for_each_drv+0x51/0x7c)
[<c05b9005>] (bus_for_each_drv) from [<c05ba9f7>] (__device_attach+0x8b/0x104)
[<c05ba9f7>] (__device_attach) from [<c05b9b1b>] (bus_probe_device+0x5b/0x60)
[<c05b9b1b>] (bus_probe_device) from [<c05b9dfb>] (deferred_probe_work_func+0x57/0x78)
[<c05b9dfb>] (deferred_probe_work_func) from [<c013701f>] (process_one_work+0x147/0x3f8)
[<c013701f>] (process_one_work) from [<c0137805>] (worker_thread+0x21d/0x3f4)
[<c0137805>] (worker_thread) from [<c013c1bb>] (kthread+0x123/0x140)
[<c013c1bb>] (kthread) from [<c0100135>] (ret_from_fork+0x11/0x1c)
Exception stack(0xc1567fb0 to 0xc1567ff8)
---[ end trace f68728a0d3053b54 ]---
tegra-gr3d 54180000.gr3d: failed to set OPP clk: -EBUSY
genpd genpd:1:54180000.gr3d: failed to get performance state of 54180000.gr3d for power-domain 3d1: -16
tegra-gr3d 54180000.gr3d: Couldn't attach to pm_domain: -16