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Date:   Tue, 19 Nov 2019 12:00:53 +0000
From:   sibis@codeaurora.org
To:     Evan Green <evgreen@chromium.org>
Cc:     Rob Herring <robh+dt@kernel.org>,
        Georgi Djakov <georgi.djakov@linaro.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Andy Gross <agross@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        David Dai <daidavid1@codeaurora.org>,
        Saravana Kannan <saravanak@google.com>,
        Viresh Kumar <viresh.kumar@linaro.org>
Subject: Re: [PATCH v3 2/2] interconnect: qcom: Add OSM L3 interconnect
 provider support
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Hey Evan,
Thanks for taking time to review
the series.

On 2019-11-19 04:12, Evan Green wrote:
> Hi Sibi,
> 
> On Mon, Nov 18, 2019 at 7:45 AM Sibi Sankar <sibis@codeaurora.org> 
> wrote:
>> 
>> On some Qualcomm SoCs, Operating State Manager (OSM) controls the
>> resources of scaling L3 caches. Add a driver to handle bandwidth
>> requests to OSM L3 from CPU/GPU.
>> 
>> Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
>> ---
>>  drivers/interconnect/qcom/Kconfig  |   7 +
>>  drivers/interconnect/qcom/Makefile |   2 +
>>  drivers/interconnect/qcom/osm-l3.c | 284 
>> +++++++++++++++++++++++++++++
>>  3 files changed, 293 insertions(+)
>>  create mode 100644 drivers/interconnect/qcom/osm-l3.c
>> 
>> diff --git a/drivers/interconnect/qcom/Kconfig 
>> b/drivers/interconnect/qcom/Kconfig
>> index ecf057d7e2409..17aee5b0f15b7 100644
>> --- a/drivers/interconnect/qcom/Kconfig
>> +++ b/drivers/interconnect/qcom/Kconfig
>> @@ -5,6 +5,13 @@ config INTERCONNECT_QCOM
>>         help
>>           Support for Qualcomm's Network-on-Chip interconnect 
>> hardware.
>> 
>> +config INTERCONNECT_QCOM_OSM_L3
>> +       tristate "Qualcomm OSM L3 interconnect driver"
>> +       depends on INTERCONNECT_QCOM || COMPILE_TEST
> 
> Should we depend on something sdm845 here?

not really...

maybe I can have 845 interconnect
selecting osm_l3? since sc7180 also
would be doing the same.

> 
>> +       help
>> +         Say y here to support the Operating State Manager (OSM) 
>> interconnect
>> +         driver which controls the scaling of L3 caches on Qualcomm 
>> SoCs.
>> +
>>  config INTERCONNECT_QCOM_QCS404
>>         tristate "Qualcomm QCS404 interconnect driver"
>>         depends on INTERCONNECT_QCOM
>> diff --git a/drivers/interconnect/qcom/Makefile 
>> b/drivers/interconnect/qcom/Makefile
>> index 9adf9e380545e..8d86d6515ffc9 100644
>> --- a/drivers/interconnect/qcom/Makefile
>> +++ b/drivers/interconnect/qcom/Makefile
>> @@ -1,10 +1,12 @@
>>  # SPDX-License-Identifier: GPL-2.0
>> 
>> +icc-osm-l3-objs                                := osm-l3.o
>>  qnoc-msm8974-objs                      := msm8974.o
>>  qnoc-qcs404-objs                       := qcs404.o
>>  qnoc-sdm845-objs                       := sdm845.o
>>  icc-smd-rpm-objs                       := smd-rpm.o
>> 
>> +obj-$(CONFIG_INTERCONNECT_QCOM_OSM_L3) += icc-osm-l3.o
>>  obj-$(CONFIG_INTERCONNECT_QCOM_MSM8974) += qnoc-msm8974.o
>>  obj-$(CONFIG_INTERCONNECT_QCOM_QCS404) += qnoc-qcs404.o
>>  obj-$(CONFIG_INTERCONNECT_QCOM_SDM845) += qnoc-sdm845.o
>> diff --git a/drivers/interconnect/qcom/osm-l3.c 
>> b/drivers/interconnect/qcom/osm-l3.c
>> new file mode 100644
>> index 0000000000000..5e9f9ce02863b
>> --- /dev/null
>> +++ b/drivers/interconnect/qcom/osm-l3.c
>> @@ -0,0 +1,284 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (c) 2019, The Linux Foundation. All rights reserved.
>> + *
>> + */
>> +
>> +#include <dt-bindings/interconnect/qcom,osm-l3.h>
>> +#include <dt-bindings/interconnect/qcom,sdm845.h>
>> +#include <linux/bitfield.h>
>> +#include <linux/clk.h>
>> +#include <linux/interconnect-provider.h>
>> +#include <linux/io.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +#include <linux/of_device.h>
>> +#include <linux/of_platform.h>
>> +#include <linux/platform_device.h>
>> +
>> +#define LUT_MAX_ENTRIES                        40U
>> +#define LUT_SRC                                GENMASK(31, 30)
>> +#define LUT_L_VAL                      GENMASK(7, 0)
>> +#define LUT_ROW_SIZE                   32
>> +#define CLK_HW_DIV                     2
>> +
>> +/* Register offsets */
>> +#define REG_ENABLE                     0x0
>> +#define REG_FREQ_LUT                   0x110
>> +#define REG_PERF_STATE                 0x920
>> +
>> +#define OSM_L3_MAX_LINKS               1
>> +
>> +#define to_qcom_provider(_provider) \
>> +       container_of(_provider, struct qcom_osm_l3_icc_provider, 
>> provider)
>> +
>> +enum {
>> +       SDM845_MASTER_OSM_L3_APPS = SLAVE_TCU + 1,
>> +       SDM845_SLAVE_OSM_L3,
>> +};
> 
> Should these just go in qcom,sdm845.h? Seems nice to have them all in
> one place, and then they can be accessed in the DT if needed.

yeah I can do that, by doing
this I can also get rid of the
SLAVE_TCU + 1 :)

> 
>> +
>> +struct qcom_osm_l3_icc_provider {
>> +       void __iomem *base;
>> +       unsigned int max_state;
>> +       unsigned long lut_tables[LUT_MAX_ENTRIES];
>> +       struct icc_provider provider;
>> +};
>> +
>> +/**
>> + * struct qcom_icc_node - Qualcomm specific interconnect nodes
>> + * @name: the node name used in debugfs
>> + * @links: an array of nodes where we can go next while traversing
>> + * @id: a unique node identifier
>> + * @num_links: the total number of @links
>> + * @buswidth: width of the interconnect between a node and the bus
>> + */
>> +struct qcom_icc_node {
>> +       const char *name;
>> +       u16 links[OSM_L3_MAX_LINKS];
>> +       u16 id;
>> +       u16 num_links;
>> +       u16 buswidth;
>> +};
>> +
>> +struct qcom_icc_desc {
>> +       struct qcom_icc_node **nodes;
>> +       size_t num_nodes;
>> +};
>> +
>> +#define DEFINE_QNODE(_name, _id, _buswidth, ...)                      
>>  \
>> +               static struct qcom_icc_node _name = {                  
>>  \
>> +               .name = #_name,                                        
>>  \
>> +               .id = _id,                                             
>>  \
>> +               .buswidth = _buswidth,                                 
>>  \
>> +               .num_links = ARRAY_SIZE(((int[]){ __VA_ARGS__ })),     
>>  \
>> +               .links = { __VA_ARGS__ },                              
>>  \
>> +       }
>> +
>> +DEFINE_QNODE(osm_apps_l3, SDM845_MASTER_OSM_L3_APPS, 16, 
>> SDM845_SLAVE_OSM_L3);
>> +DEFINE_QNODE(osm_l3, SDM845_SLAVE_OSM_L3, 16);
>> +
>> +static struct qcom_icc_node *sdm845_osm_l3_nodes[] = {
> 
> const?

unfortunately we can't ...

data->nodes[i] = node;
we setup links later ^^ with
the pointer.

> 
>> +       [MASTER_OSM_L3_APPS] = &osm_apps_l3,
>> +       [SLAVE_OSM_L3] = &osm_l3,
>> +};
>> +
>> +static struct qcom_icc_desc sdm845_osm_l3 = {
>> +       .nodes = sdm845_osm_l3_nodes,
>> +       .num_nodes = ARRAY_SIZE(sdm845_osm_l3_nodes),
>> +};
>> +
>> +static int qcom_icc_aggregate(struct icc_node *node, u32 tag, u32 
>> avg_bw,
>> +                             u32 peak_bw, u32 *agg_avg, u32 
>> *agg_peak)
>> +{
>> +       *agg_avg += avg_bw;
>> +       *agg_peak = max_t(u32, *agg_peak, peak_bw);
>> +
>> +       return 0;
>> +}
> 
> Georgi, I wonder if it's a good idea to make a small collection of
> "std" aggregate functions in the interconnect core that a driver can
> just point to if it's doing something super standard like this (ie
> driver->aggregate = icc_std_aggregate;). This is probably fine as-is
> for now, but if we see a lot more copy/pastes of this function we
> should think about it.
> 
>> +
>> +static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
>> +{
>> +       struct qcom_osm_l3_icc_provider *qp;
>> +       struct icc_provider *provider;
>> +       struct qcom_icc_node *qn;
>> +       struct icc_node *n;
>> +       unsigned int index;
>> +       u32 agg_peak = 0;
>> +       u32 agg_avg = 0;
>> +       u64 rate;
>> +
>> +       qn = src->data;
>> +       provider = src->provider;
>> +       qp = to_qcom_provider(provider);
>> +
>> +       list_for_each_entry(n, &provider->nodes, node_list)
>> +               qcom_icc_aggregate(n, 0, n->avg_bw, n->peak_bw,
>> +                                  &agg_avg, &agg_peak);
>> +
>> +       rate = max(agg_avg, agg_peak);
>> +       rate = icc_units_to_bps(rate);
>> +       do_div(rate, qn->buswidth);
>> +
>> +       for (index = 0; index < qp->max_state; index++) {
> 
> If the rate is too high, you'll end up setting max_state into the
> register. That's probably bad, right? (Or maybe it's not because the
> table ends with the same value twice, but it seems like relying on an
> implementation detail). We could guard against that by only iterating
> to index < qp->max_state - 1.

yes, using max_state - 1 makes sense
here. Will change this in the next
re-spin.

> 
>> +               if (qp->lut_tables[index] >= rate)
>> +                       break;
>> +       }
>> +
>> +       writel_relaxed(index, qp->base + REG_PERF_STATE);
>> +
>> +       return 0;
>> +}
>> +
>> +static int qcom_osm_l3_remove(struct platform_device *pdev)
>> +{
>> +       struct qcom_osm_l3_icc_provider *qp = 
>> platform_get_drvdata(pdev);
>> +       struct icc_provider *provider = &qp->provider;
>> +       struct icc_node *n;
>> +
>> +       list_for_each_entry(n, &provider->nodes, node_list) {
> 
> There was a comment on one of the other threads that we've been
> copy/pasting this snippet around and it's wrong because it doesn't use
> the _safe variant of the macro. So we end up destroying the list we're
> iterating over.
> 
> Georgi, did you have a plan to refactor this, or should we just change
> this to be the _safe version?
> 
>> +               icc_node_del(n);
>> +               icc_node_destroy(n->id);
>> +       }
>> +
>> +       return icc_provider_del(provider);
>> +}
>> +
>> +static int qcom_osm_l3_probe(struct platform_device *pdev)
>> +{
>> +       u32 info, src, lval, i, prev_freq = 0, freq;
>> +       static unsigned long hw_rate, xo_rate;
>> +       struct qcom_osm_l3_icc_provider *qp;
>> +       const struct qcom_icc_desc *desc;
>> +       struct icc_onecell_data *data;
>> +       struct icc_provider *provider;
>> +       struct qcom_icc_node **qnodes;
>> +       struct icc_node *node;
>> +       size_t num_nodes;
>> +       struct clk *clk;
>> +       int ret;
>> +
>> +       clk = clk_get(&pdev->dev, "xo");
>> +       if (IS_ERR(clk))
>> +               return PTR_ERR(clk);
>> +
>> +       xo_rate = clk_get_rate(clk);
>> +       clk_put(clk);
>> +
>> +       clk = clk_get(&pdev->dev, "alternate");
>> +       if (IS_ERR(clk))
>> +               return PTR_ERR(clk);
>> +
>> +       hw_rate = clk_get_rate(clk) / CLK_HW_DIV;
> 
> It's a little weird there's a constant divide in there, though I guess
> it's in the cpufreq driver as well. I guess this is fine if it's
> likely to stay there (and the same) when this driver is generalized
> for other SoCs.

yeah I don't see this changing
on sc7180 so I'll leave this
as is.

> 
>> +       clk_put(clk);
>> +
>> +       qp = devm_kzalloc(&pdev->dev, sizeof(*qp), GFP_KERNEL);
>> +       if (!qp)
>> +               return -ENOMEM;
>> +
>> +       qp->base = devm_platform_ioremap_resource(pdev, 0);
>> +       if (IS_ERR(qp->base))
>> +               return PTR_ERR(qp->base);
>> +
>> +       /* HW should be in enabled state to proceed */
>> +       if (!(readl_relaxed(qp->base + REG_ENABLE) & 0x1)) {
>> +               dev_err(&pdev->dev, "error hardware not enabled\n");
>> +               return -ENODEV;
>> +       }
>> +
>> +       for (i = 0; i < LUT_MAX_ENTRIES; i++) {
>> +               info = readl_relaxed(qp->base + REG_FREQ_LUT +
>> +                                    i * LUT_ROW_SIZE);
>> +               src = FIELD_GET(LUT_SRC, info);
>> +               lval = FIELD_GET(LUT_L_VAL, info);
>> +               if (src)
>> +                       freq = xo_rate * lval;
>> +               else
>> +                       freq = hw_rate;
>> +
>> +               /*
>> +                * Two of the same frequencies with the same core 
>> counts means
> 
> "core counts" seems like a copied comment that doesn't apply.

yes we don't use the core_cnt
field so will update the comment.

> 
> But you only look at freq and not core count, is that really
> equivalent to the table's boundary condition? Or do you need to be
> comparing info == info_prev?

no we can get by comparing
current freq with prev freq
on OSM L3.

> 
>> +                * end of table
>> +                */
>> +               if (i > 0 && prev_freq == freq)
>> +                       break;
>> +
>> +               qp->lut_tables[i] = freq;
>> +               prev_freq = freq;
>> +       }
>> +       qp->max_state = i;
> 
> Should we error out or complain if there are too few entries, or if
> the table is not in increasing order?

OSM does make sure of the
increasing order and correct
number of freq entries if the
REG_ENABLE is set. However I
don't really mind adding the
increasing order check but we
can't really detect too few
entries since the number can
vary across SKUs.

> 
>> +
>> +       desc = of_device_get_match_data(&pdev->dev);
>> +       if (!desc)
>> +               return -EINVAL;
>> +
>> +       qnodes = desc->nodes;
>> +       num_nodes = desc->num_nodes;
>> +
>> +       data = devm_kcalloc(&pdev->dev, num_nodes, sizeof(*node), 
>> GFP_KERNEL);
>> +       if (!data)
>> +               return -ENOMEM;
>> +
>> +       provider = &qp->provider;
>> +       provider->dev = &pdev->dev;
>> +       provider->set = qcom_icc_set;
>> +       provider->aggregate = qcom_icc_aggregate;
>> +       provider->xlate = of_icc_xlate_onecell;
>> +       INIT_LIST_HEAD(&provider->nodes);
>> +       provider->data = data;
>> +
>> +       ret = icc_provider_add(provider);
>> +       if (ret) {
>> +               dev_err(&pdev->dev, "error adding interconnect 
>> provider\n");
>> +               return ret;
>> +       }
>> +
>> +       for (i = 0; i < num_nodes; i++) {
>> +               size_t j;
>> +
>> +               node = icc_node_create(qnodes[i]->id);
>> +               if (IS_ERR(node)) {
>> +                       ret = PTR_ERR(node);
>> +                       goto err;
>> +               }
>> +
>> +               node->name = qnodes[i]->name;
>> +               node->data = qnodes[i];
>> +               icc_node_add(node, provider);
>> +
>> +               dev_dbg(&pdev->dev, "registered node %p %s %d\n", 
>> node,
>> +                       qnodes[i]->name, node->id);
>> +
>> +               /* populate links */
> 
> Not a super useful comment.

lol will remove it

> 
> 
>> +               for (j = 0; j < qnodes[i]->num_links; j++)
>> +                       icc_link_create(node, qnodes[i]->links[j]);
>> +
>> +               data->nodes[i] = node;
>> +       }
>> +       data->num_nodes = num_nodes;
>> +
>> +       platform_set_drvdata(pdev, qp);
>> +
>> +       return ret;
>> +err:
>> +       qcom_osm_l3_remove(pdev);
>> +       return ret;
>> +}
>> +
>> +static const struct of_device_id osm_l3_of_match[] = {
>> +       { .compatible = "qcom,sdm845-osm-l3", .data = &sdm845_osm_l3 
>> },
>> +       { },
>> +};
>> +MODULE_DEVICE_TABLE(of, osm_l3_of_match);
>> +
>> +static struct platform_driver osm_l3_driver = {
>> +       .probe = qcom_osm_l3_probe,
>> +       .remove = qcom_osm_l3_remove,
>> +       .driver = {
>> +               .name = "osm-l3",
>> +               .of_match_table = osm_l3_of_match,
>> +       },
>> +};
>> +module_platform_driver(osm_l3_driver);
>> +
>> +MODULE_DESCRIPTION("Qualcomm OSM L3 interconnect driver");
>> +MODULE_LICENSE("GPL v2");
>> --
>> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora 
>> Forum,
>> a Linux Foundation Collaborative Project
>>