Date:   Wed, 14 Aug 2019 17:00:49 +0530
From:   Sibi Sankar <sibis@...eaurora.org>
To:     Saravana Kannan <saravanak@...gle.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        agross@...nel.org, LKML <linux-kernel@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, linux-arm-msm@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Evan Green <evgreen@...omium.org>,
        David Dai <daidavid1@...eaurora.org>,
        linux-kernel-owner@...r.kernel.org
Subject: Re: [PATCH 2/2] interconnect: qcom: Add OSM L3 interconnect provider
 support

On 2019-08-14 06:13, Saravana Kannan wrote:
> On Thu, Aug 8, 2019 at 10:37 AM Sibi Sankar <sibis@...eaurora.org> 
> wrote:
>> 
>> Hey Saravana,
>> 
>> Thanks for the review!
>> 
>> On 8/8/19 2:51 AM, Saravana Kannan wrote:
>> > On Wed, Aug 7, 2019 at 4:24 AM Sibi Sankar <sibis@...eaurora.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@...eaurora.org>
>> >> ---
>> >>   drivers/interconnect/qcom/Kconfig  |   7 +
>> >>   drivers/interconnect/qcom/Makefile |   2 +
>> >>   drivers/interconnect/qcom/osm-l3.c | 292 +++++++++++++++++++++++++++++
>> >>   3 files changed, 301 insertions(+)
>> >>   create mode 100644 drivers/interconnect/qcom/osm-l3.c
>> >>
>> >> diff --git a/drivers/interconnect/qcom/Kconfig b/drivers/interconnect/qcom/Kconfig
>> >> index d5e70ebc24108..f6c2a11a1a2c9 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
>> >> +       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_SDM845
>> >>          tristate "Qualcomm SDM845 interconnect driver"
>> >>          depends on INTERCONNECT_QCOM
>> >> diff --git a/drivers/interconnect/qcom/Makefile b/drivers/interconnect/qcom/Makefile
>> >> index 1c1cea690f922..9078af5fed109 100644
>> >> --- a/drivers/interconnect/qcom/Makefile
>> >> +++ b/drivers/interconnect/qcom/Makefile
>> >> @@ -1,5 +1,7 @@
>> >>   # SPDX-License-Identifier: GPL-2.0
>> >>
>> >> +icc-osm-l3-objs                                := osm-l3.o
>> >>   qnoc-sdm845-objs                       := sdm845.o
>> >>
>> >> +obj-$(CONFIG_INTERCONNECT_QCOM_OSM_L3) += icc-osm-l3.o
>> >>   obj-$(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..1e7dfce6f4f9b
>> >> --- /dev/null
>> >> +++ b/drivers/interconnect/qcom/osm-l3.c
>> >> @@ -0,0 +1,292 @@
>> >> +// 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_icc_provider, provider)
>> >> +
>> >> +enum {
>> >> +       SDM845_MASTER_OSM_L3_APPS = SLAVE_TCU + 1,
>> >> +       SDM845_MASTER_OSM_L3_GPU,
>> >> +       SDM845_SLAVE_OSM_L3,
>> >> +};
>> >> +
>> >> +struct qcom_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_gpu_l3, SDM845_MASTER_OSM_L3_GPU, 16, SDM845_SLAVE_OSM_L3);
>> >> +DEFINE_QNODE(osm_l3, SDM845_SLAVE_OSM_L3, 16);
>> >> +
>> >> +static struct qcom_icc_node *sdm845_osm_l3_nodes[] = {
>> >> +       [MASTER_OSM_L3_APPS] = &osm_apps_l3,
>> >> +       [MASTER_OSM_L3_GPU] = &osm_gpu_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 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;
>> >> +}
>> >> +
>> >> +static int qcom_icc_set(struct icc_node *src, struct icc_node *dst)
>> >> +{
>> >> +       struct icc_provider *provider;
>> >> +       struct qcom_icc_provider *qp;
>> >> +       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, 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 (qp->lut_tables[index] >= rate)
>> >> +                       break;
>> >> +       }
>> >> +
>> >> +       writel_relaxed(index, qp->base + REG_PERF_STATE);
>> >> +
>> >> +       return 0;
>> >> +}
>> >> +
>> >> +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;
>> >> +       const struct qcom_icc_desc *desc;
>> >> +       struct icc_onecell_data *data;
>> >> +       struct icc_provider *provider;
>> >> +       struct qcom_icc_node **qnodes;
>> >> +       struct qcom_icc_provider *qp;
>> >> +       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;
>> >> +       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
>> >> +                * end of table
>> >> +                */
>> >> +               if (i > 0 && prev_freq == freq)
>> >> +                       break;
>> >> +
>> >> +               qp->lut_tables[i] = freq;
>> >> +               prev_freq = freq;
>> >> +       }
>> >> +       qp->max_state = i;
>> >> +
>> >> +       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 */
>> >> +               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:
>> >> +       list_for_each_entry(node, &provider->nodes, node_list) {
>> >> +               icc_node_del(node);
>> >> +               icc_node_destroy(node->id);
>> >> +       }
>> >> +
>> >> +       icc_provider_del(provider);
>> >> +       return ret;
>> >> +}
>> >> +
>> >> +static int qcom_osm_l3_remove(struct platform_device *pdev)
>> >> +{
>> >> +       struct qcom_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) {
>> >> +               icc_node_del(n);
>> >> +               icc_node_destroy(n->id);
>> >> +       }
>> >> +
>> >> +       return icc_provider_del(provider);
>> >> +}
>> >> +
>> >> +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");
>> >
>> > Did a quick scan of the code and it's not clear how you connect the L3
>> > interconnect provider to the rest of the interconnect. I don't see any
>> > DT or code references to the rest of the interconnects in the system.
>> > If GPU is making a bandwidth request all the way to L3, how do you
>> > make sure the interconnects between GPU and L3 also scale up properly.
>> 
>> For SDM845 OSM L3 provider the icc nodes endpoints are isolated from
>> rsc icc node endpoints i.e GPU would need to vote on this path in
>> addition to voting for DDR. On future SoCs if the need to scale
>> interconnect between GPU rsc nodes along with the OSM l3 nodes arises,
>> it can be trivially extended by linking the osm icc nodes with global
>> icc node ids of the gpu rsc nodes.
> 
> Sorry, I'm not sure we are talking about the same thing. To keep the
> discussion focused, let's completely ignore GPU's DDR needs for now.
> 
> Talking about GPU <-> L3 traffic, unless the GPU is directly connected
> to the L3 with no additional interconnects in between (unlikely), this
> L3 provider need to connect the L3 icc node with the rest of the
> interconnect nodes. Otherwise, even if the L3 itself is provisioned to
> handle, say 10 GB/s, the interconnects connecting the GPU to L3 might
> be left at 1 GB/s.
> 
> So, can we please connect this node to the rest of the interconnect
> nodes in SDM845?

Sure I'll double check if GPU has a l3
scaling requirement on SDM845 SoCs and
drop/link it to the rsc nodes appropriately.

> 
> Thanks,
> Saravana

-- 
-- Sibi Sankar --
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project.

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