Re: [RFC PATCH 3/4] PM / devfreq: rockchip: add devfreq driver for rk3399 dmc

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Hi Myungloo Ham,


On 2016年06月01日 18:47, MyungJoo Ham wrote:
On Wed, Jun 1, 2016 at 6:35 PM, Lin Huang <hl@xxxxxxxxxxxxxx> wrote:
there is dfi controller on rk3399 platform, it can monitor
ddr load, register this controller to devfreq framework, and
default to use simple_ondeamnd policy, and do ddr frequency
scaling base on this result.

Signed-off-by: Lin Huang <hl@xxxxxxxxxxxxxx>
---
  drivers/devfreq/Kconfig                 |   2 +-
  drivers/devfreq/Makefile                |   1 +
  drivers/devfreq/rockchip/Kconfig        |  14 +
  drivers/devfreq/rockchip/Makefile       |   2 +
  drivers/devfreq/rockchip/rk3399_dmc.c   | 438 ++++++++++++++++++++++++++++++++
  drivers/devfreq/rockchip/rockchip_dmc.c | 132 ++++++++++
  include/soc/rockchip/rockchip_dmc.h     |  44 ++++
  7 files changed, 632 insertions(+), 1 deletion(-)
  create mode 100644 drivers/devfreq/rockchip/Kconfig
  create mode 100644 drivers/devfreq/rockchip/Makefile
  create mode 100644 drivers/devfreq/rockchip/rk3399_dmc.c
  create mode 100644 drivers/devfreq/rockchip/rockchip_dmc.c
  create mode 100644 include/soc/rockchip/rockchip_dmc.h

+
+       /* check the rate we get whether correct */
+       dmcfreq->rate = clk_get_rate(dmcfreq->dmc_clk);
+       if (dmcfreq->rate != target_rate) {
+               dev_err(dev, "get wrong ddr frequency, Request freq %lu,\
+                       Current freq %lu\n", target_rate, dmcfreq->rate);
+               regulator_set_voltage(dmcfreq->vdd_center, dmcfreq->volt,
+                                     dmcfreq->volt);
Why do you need to check this and
more importantly, why do you assume that dmvfreq->volt
will be safe in this case? (what if the new dmcfreq->rate is
larger than the old dmcfreq->rate after clk_get_rate?)
Note that you didn't update dmcfreq->volt after clk_get_rate()
Now we will set the ddr clock rate in bl31 use dcf controller(as i show in the patch cover letter), and there only two result we can get, set clock rate fail(ddr clock still in old rate) or set clock rate sucessful(use the new ddr rate), if the set rate fail, we should keep the voltage old value. Ah, you
    remind me, i should check clock rate before:
        if (old_clk_rate > target_rate)
    otherwise there have chance set high rate fail and use low voltage.

And about the dmcfreq->volt, i will update this value when into the function, throuth

    opp = devfreq_recommended_opp(dev, &dmcfreq->rate, flags);
    if (IS_ERR(opp)) {
        rcu_read_unlock();
        return PTR_ERR(opp);
    }
    dmcfreq->volt = dev_pm_opp_get_voltage(opp);

+EXPORT_SYMBOL_GPL(dmc_event);
+EXPORT_SYMBOL_GPL(rockchip_dmc_enabled);
+EXPORT_SYMBOL_GPL(rockchip_dmc_enable);
+EXPORT_SYMBOL_GPL(rockchip_dmc_disable);
+EXPORT_SYMBOL_GPL(dmc_register_notifier);
+EXPORT_SYMBOL_GPL(dmc_unregister_notifier);
+EXPORT_SYMBOL_GPL(rockchip_dmc_get);
+EXPORT_SYMBOL_GPL(rockchip_dmc_put);
Do you really need to export all these device driver specific
functions? Looks like a design flaw here.

there is some situation we need to disable ddr frequency scaling(connect two panel etc) on rk3399 platform, and it should be also needed on other rockchip platform, so i move these
    funticon as separate file.

Cheers,
MyungJoo



--
Lin Huang


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