Date:   Wed, 14 Aug 2019 09:21:16 -0600
From:   Jordan Crouse <jcrouse@...eaurora.org>
To:     Sibi Sankar <sibis@...eaurora.org>
Cc:     Saravana Kannan <saravanak@...gle.com>,
        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 Wed, Aug 14, 2019 at 05:00:49PM +0530, Sibi Sankar wrote:
> 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.

GPU doesn't use I/O coherency at the moment and I don't think we would need an
independent connection if we did.

Jordan

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

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

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