RE: [PATCH v7 12/14] cpufreq: Add Kryo CPU scaling driver

[<ilialin@codeaurora.org>]

> -----Original Message-----
> From: amit.kucheria@verdurent.com <amit.kucheria@verdurent.com> On
> Behalf Of Amit Kucheria
> Sent: Wednesday, May 16, 2018 16:13
> To: Ilia Lin <ilialin@codeaurora.org>
> Cc: Michael Turquette <mturquette@baylibre.com>; sboyd@kernel.org; Rob
> Herring <robh@kernel.org>; Mark Rutland <mark.rutland@arm.com>; Viresh
> Kumar <viresh.kumar@linaro.org>; nm@ti.com; lgirdwood@gmail.com;
> broonie@kernel.org; Andy Gross <andy.gross@linaro.org>; David Brown
> <david.brown@linaro.org>; catalin.marinas@arm.com;
> will.deacon@arm.com; Rafael J. Wysocki <rjw@rjwysocki.net>; linux-
> clk@vger.kernel.org; devicetree@vger.kernel.org; LKML <linux-
> kernel@vger.kernel.org>; Linux PM list <linux-pm@vger.kernel.org>; linux-
> arm-msm@vger.kernel.org; linux-soc@vger.kernel.org; lakml <linux-arm-
> kernel@lists.infradead.org>; Rajendra Nayak <rnayak@codeaurora.org>;
> nicolas.dechesne@linaro.org; celster@codeaurora.org;
> tfinkel@codeaurora.org
> Subject: Re: [PATCH v7 12/14] cpufreq: Add Kryo CPU scaling driver
> 
> On Tue, May 15, 2018 at 12:13 PM, Ilia Lin <ilialin@codeaurora.org> wrote:
> > In Certain QCOM SoCs like apq8096 and msm8996 that have KRYO
> > processors, the CPU ferequencies subset and voltage value of each OPP
> > varies
> 
> s/ferequencies/frequency
> 
> > based on the silicon variant in use. Qualcomm Process Voltage Scaling
> > Tables defines the voltage and frequency value based on the msm-id in
> > SMEM and speedbin blown in the efuse combination.
> > The qcom-cpufreq-kryo driver reads the msm-id and efuse value from the
> > SoC to provide the OPP framework with required information.
> > This is used to determine the voltage and frequency value for each OPP
> > of
> > operating-points-v2 table when it is parsed by the OPP framework.
> >
> > Signed-off-by: Ilia Lin <ilialin@codeaurora.org>
> > ---
> >  drivers/cpufreq/Kconfig.arm          |  11 +++
> >  drivers/cpufreq/Makefile             |   1 +
> >  drivers/cpufreq/cpufreq-dt-platdev.c |   3 +
> >  drivers/cpufreq/qcom-cpufreq-kryo.c  | 150
> > +++++++++++++++++++++++++++++++++++
> >  4 files changed, 165 insertions(+)
> >  create mode 100644 drivers/cpufreq/qcom-cpufreq-kryo.c
> >
> > diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> > index de55c7d..5c16f05 100644
> > --- a/drivers/cpufreq/Kconfig.arm
> > +++ b/drivers/cpufreq/Kconfig.arm
> > @@ -124,6 +124,17 @@ config ARM_OMAP2PLUS_CPUFREQ
> >         depends on ARCH_OMAP2PLUS
> >         default ARCH_OMAP2PLUS
> >
> > +config ARM_QCOM_CPUFREQ_KRYO
> > +       bool "Qualcomm Technologies, Inc. Kryo based CPUFreq"
> 
> "Qualcomm Kryo CPUFreq support" should be enough. Kconfig isn't the place
> for Trademark compliance :-)

This is mandatory requirement of the QTIs legal.

> 
> > +       depends on QCOM_QFPROM
> > +       depends on QCOM_SMEM
> > +       select PM_OPP
> > +       help
> > +         This adds the CPUFreq driver for
> > +         Qualcomm Technologies, Inc. Kryo SoC based boards.
> > +
> > +         If in doubt, say N.
> > +
> >  config ARM_S3C_CPUFREQ
> >         bool
> >         help
> > diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile index
> > 8d24ade..fb4a2ec 100644
> > --- a/drivers/cpufreq/Makefile
> > +++ b/drivers/cpufreq/Makefile
> > @@ -65,6 +65,7 @@ obj-$(CONFIG_MACH_MVEBU_V7)           += mvebu-
> cpufreq.o
> >  obj-$(CONFIG_ARM_OMAP2PLUS_CPUFREQ)    += omap-cpufreq.o
> >  obj-$(CONFIG_ARM_PXA2xx_CPUFREQ)       += pxa2xx-cpufreq.o
> >  obj-$(CONFIG_PXA3xx)                   += pxa3xx-cpufreq.o
> > +obj-$(CONFIG_ARM_QCOM_CPUFREQ_KRYO)    += qcom-cpufreq-kryo.o
> >  obj-$(CONFIG_ARM_S3C2410_CPUFREQ)      += s3c2410-cpufreq.o
> >  obj-$(CONFIG_ARM_S3C2412_CPUFREQ)      += s3c2412-cpufreq.o
> >  obj-$(CONFIG_ARM_S3C2416_CPUFREQ)      += s3c2416-cpufreq.o
> > diff --git a/drivers/cpufreq/cpufreq-dt-platdev.c
> > b/drivers/cpufreq/cpufreq-dt-platdev.c
> > index 3b585e4..77d6ab8 100644
> > --- a/drivers/cpufreq/cpufreq-dt-platdev.c
> > +++ b/drivers/cpufreq/cpufreq-dt-platdev.c
> > @@ -118,6 +118,9 @@
> >
> >         { .compatible = "nvidia,tegra124", },
> >
> > +       { .compatible = "qcom,apq8096", },
> > +       { .compatible = "qcom,msm8996", },
> > +
> >         { .compatible = "st,stih407", },
> >         { .compatible = "st,stih410", },
> >
> > diff --git a/drivers/cpufreq/qcom-cpufreq-kryo.c
> > b/drivers/cpufreq/qcom-cpufreq-kryo.c
> > new file mode 100644
> > index 0000000..10d7236
> > --- /dev/null
> > +++ b/drivers/cpufreq/qcom-cpufreq-kryo.c
> > @@ -0,0 +1,150 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> 
> Stray space here.
> 
> > + * Copyright (c) 2018, The Linux Foundation. All rights reserved.
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + modify
> > + * it under the terms of the GNU General Public License version 2 and
> > + * only version 2 as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + */
> > +
> > +#include <linux/cpu.h>
> > +#include <linux/err.h>
> > +#include <linux/init.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/nvmem-consumer.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pm_opp.h>
> > +#include <linux/slab.h>
> > +#include <linux/soc/qcom/smem.h>
> > +
> > +#define MSM_ID_SMEM    137
> > +#define SILVER_LEAD    0
> > +#define GOLD_LEAD      2
> > +
> > +enum _msm_id {
> > +       MSM8996V3 = 0xF6ul,
> > +       APQ8096V3 = 0x123ul,
> > +       MSM8996SG = 0x131ul,
> > +       APQ8096SG = 0x138ul,
> > +};
> > +
> > +enum _msm8996_version {
> > +       MSM8996_V3,
> > +       MSM8996_SG,
> > +       NUM_OF_MSM8996_VERSIONS,
> > +};
> > +
> > +static enum _msm8996_version __init
> > +qcom_cpufreq_kryo_get_msm_id(void)
> > +{
> > +       size_t len;
> > +       u32 *msm_id;
> > +       enum _msm8996_version version;
> > +
> > +       msm_id = qcom_smem_get(QCOM_SMEM_HOST_ANY,
> MSM_ID_SMEM, &len);
> > +       /* The first 4 bytes are format, next to them is the actual msm-id */
> > +       msm_id++;
> > +
> > +       switch ((enum _msm_id)*msm_id) {
> > +       case MSM8996V3:
> > +       case APQ8096V3:
> > +               version = MSM8996_V3;
> > +               break;
> > +       case MSM8996SG:
> > +       case APQ8096SG:
> > +               version = MSM8996_SG;
> > +               break;
> > +       default:
> > +               version = NUM_OF_MSM8996_VERSIONS;
> > +       }
> > +
> > +       return version;
> > +}
> > +
> > +static int __init qcom_cpufreq_kryo_driver_init(void)
> > +{
> > +       size_t len;
> > +       int ret;
> > +       u32 versions;
> > +       enum _msm8996_version msm8996_version;
> > +       u8 *speedbin;
> > +       struct device *cpu_dev;
> > +       struct device_node *np;
> > +       struct nvmem_cell *speedbin_nvmem;
> > +       struct opp_table *opp_temp = NULL;
> > +
> > +       cpu_dev = get_cpu_device(SILVER_LEAD);
> > +       if (IS_ERR_OR_NULL(cpu_dev))
> > +               return PTR_ERR(cpu_dev);
> > +
> > +       msm8996_version = qcom_cpufreq_kryo_get_msm_id();
> > +       if (NUM_OF_MSM8996_VERSIONS == msm8996_version) {
> > +               dev_err(cpu_dev, "Not Snapdragon 820/821!");
> > +               return -ENODEV;
> > +        }
> 
> Use tab instead of spaces.
> 
> > +
> > +       np = dev_pm_opp_of_get_opp_desc_node(cpu_dev);
> > +       if (IS_ERR_OR_NULL(np))
> > +               return PTR_ERR(np);
> > +
> > +       if (!of_device_is_compatible(np, "operating-points-v2-kryo-cpu")) {
> > +               ret = -ENOENT;
> > +               goto free_np;
> > +       }
> > +
> > +       speedbin_nvmem = of_nvmem_cell_get(np, NULL);
> > +       if (IS_ERR(speedbin_nvmem)) {
> > +               ret = PTR_ERR(speedbin_nvmem);
> > +               dev_err(cpu_dev, "Could not get nvmem cell: %d\n", ret);
> > +               goto free_np;
> > +       }
> > +
> > +       speedbin = nvmem_cell_read(speedbin_nvmem, &len);
> > +
> > +       switch (msm8996_version) {
> > +       case MSM8996_V3:
> > +               versions = 1 << (unsigned int)(*speedbin);
> > +               break;
> > +       case MSM8996_SG:
> > +               versions = 1 << ((unsigned int)(*speedbin) + 4);
> > +               break;
> > +       default:
> > +               BUG();
> > +               break;
> > +       }
> > +
> > +       ret = PTR_ERR_OR_ZERO(opp_temp =
> > +                             dev_pm_opp_set_supported_hw(cpu_dev,&versions,1));
> > +       if (0 > ret)
> 
> Any particular reason to prefer this over (ret < 0) that is generally used? I've
> seen it used to avoid the == vs. = typos, but not for other comparisons.
> 
> Suggest sticking to what is commonly used i.e. ret < 0.
> 
> > +               goto free_opp;
> > +
> > +       cpu_dev = get_cpu_device(GOLD_LEAD);
> 
> Error check cpu_dev here?
> 
> > +       ret = PTR_ERR_OR_ZERO(opp_temp =
> > +                             dev_pm_opp_set_supported_hw(cpu_dev,&versions,1));
> > +       if (0 > ret)
> > +               goto free_opp;
> > +
> > +
> > +       ret = PTR_ERR_OR_ZERO(platform_device_register_simple("cpufreq-
> dt",
> > +                                                             -1,
> > + NULL, 0));
> > +
> > +       if (0 == ret)
> > +               return 0;
> > +
> > +free_opp:
> > +       dev_pm_opp_put_supported_hw(opp_temp);
> 
> This is not needed because dev_pm_opp_set_supported_hw will free
> memory in case of failure. This call in only needed in case of a successful get.
> 
> > +
> > +free_np:
> > +       of_node_put(np);
> > +       return ret;
> 
> 
> Suggest something like this instead:
> 
> .
> .
> 
> opp_temp = dev_pm_opp_set_supported_hw(cpu_dev,&versions,1));
> if (IS_ERR(opp_temp)) {
>      dev_err(cpu_dev, "Failed to set supported hardware\n");
>      ret = PTR_ERR(opp_temp);
>     goto free_np;
> }
> 
> cpu_dev = get_cpu_device(GOLD_LEAD);
> 
> opp_temp = dev_pm_opp_set_supported_hw(cpu_dev,&versions,1));
> if (IS_ERR(opp_temp)) {
>      dev_err(cpu_dev, "Failed to set supported hardware\n");
>      ret = PTR_ERR(opp_temp);
>     goto free_np;
> }
> 
> ret =  platform_device_register_simple("cpufreq-dt", -1, NULL, 0));
> 
> if (!IS_ERR_OR_NULL(ret))
>      goto out;
> 
> free_np:
>      of_node_put(np);
> out:
>      return ret;
> 
> > +}
> > +late_initcall(qcom_cpufreq_kryo_driver_init);
> > +
> > +MODULE_DESCRIPTION("Qualcomm Technologies, Inc. Kryo CPUfreq
> > +driver"); MODULE_LICENSE("GPL v2");
> > --
> > 1.9.1
> >