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Date: Mon, 24 Apr 2023 20:51:44 +0530
From: Sumit Gupta <sumitg@...dia.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
<treding@...dia.com>, <dmitry.osipenko@...labora.com>,
<viresh.kumar@...aro.org>, <rafael@...nel.org>,
<jonathanh@...dia.com>, <robh+dt@...nel.org>,
<lpieralisi@...nel.org>, <helgaas@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
<linux-pm@...r.kernel.org>, <devicetree@...r.kernel.org>,
<linux-pci@...r.kernel.org>, <mmaddireddy@...dia.com>,
<kw@...ux.com>, <bhelgaas@...gle.com>, <vidyas@...dia.com>,
<sanjayc@...dia.com>, <ksitaraman@...dia.com>, <ishah@...dia.com>,
<bbasu@...dia.com>, Sumit Gupta <sumitg@...dia.com>
Subject: Re: [Patch v7 1/8] memory: tegra: add interconnect support for DRAM
scaling in Tegra234
On 24/04/23 20:30, Sumit Gupta wrote:
>
>
> On 24/04/23 19:18, Krzysztof Kozlowski wrote:
>> External email: Use caution opening links or attachments
>>
>>
>> On 24/04/2023 15:13, Sumit Gupta wrote:
>>> Add Interconnect framework support to dynamically set the DRAM
>>> bandwidth from different clients. Both the MC and EMC drivers are
>>> added as ICC providers. The path for any request is:
>>> MC-Client[1-n] -> MC -> EMC -> EMEM/DRAM
>>>
>> Thank you for your patch. There is something to discuss/improve.
>>
>>
>>> +static int tegra_emc_interconnect_init(struct tegra186_emc *emc)
>>> +{
>>> + struct tegra_mc *mc = dev_get_drvdata(emc->dev->parent);
>>> + const struct tegra_mc_soc *soc = mc->soc;
>>> + struct icc_node *node;
>>> + int err;
>>> +
>>> + emc->provider.dev = emc->dev;
>>> + emc->provider.set = tegra_emc_icc_set_bw;
>>> + emc->provider.data = &emc->provider;
>>> + emc->provider.aggregate = soc->icc_ops->aggregate;
>>> + emc->provider.xlate = tegra_emc_of_icc_xlate;
>>> + emc->provider.get_bw = tegra_emc_icc_get_init_bw;
>>> +
>>> + icc_provider_init(&emc->provider);
>>> +
>>> + /* create External Memory Controller node */
>>> + node = icc_node_create(TEGRA_ICC_EMC);
>>> + if (IS_ERR(node)) {
>>> + err = PTR_ERR(node);
>>> + goto err_msg;
>>> + }
>>> +
>>> + node->name = "External Memory Controller";
>>> + icc_node_add(node, &emc->provider);
>>> +
>>> + /* link External Memory Controller to External Memory (DRAM) */
>>> + err = icc_link_create(node, TEGRA_ICC_EMEM);
>>> + if (err)
>>> + goto remove_nodes;
>>> +
>>> + /* create External Memory node */
>>> + node = icc_node_create(TEGRA_ICC_EMEM);
>>> + if (IS_ERR(node)) {
>>> + err = PTR_ERR(node);
>>> + goto remove_nodes;
>>> + }
>>> +
>>> + node->name = "External Memory (DRAM)";
>>> + icc_node_add(node, &emc->provider);
>>> +
>>> + err = icc_provider_register(&emc->provider);
>>> + if (err)
>>> + goto remove_nodes;
>>> +
>>> + return 0;
>>> +
>>> +remove_nodes:
>>> + icc_nodes_remove(&emc->provider);
>>> +err_msg:
>>> + dev_err(emc->dev, "failed to initialize ICC: %d\n", err);
>>> +
>>> + return err;
>>> +}
>>> +
>>> static int tegra186_emc_probe(struct platform_device *pdev)
>>> {
>>> + struct tegra_mc *mc = dev_get_drvdata(pdev->dev.parent);
>>> struct mrq_emc_dvfs_latency_response response;
>>> struct tegra_bpmp_message msg;
>>> struct tegra186_emc *emc;
>>> @@ -236,6 +339,29 @@ static int tegra186_emc_probe(struct
>>> platform_device *pdev)
>>> debugfs_create_file("max_rate", S_IRUGO | S_IWUSR,
>>> emc->debugfs.root,
>>> emc, &tegra186_emc_debug_max_rate_fops);
>>>
>>> + if (mc && mc->soc->icc_ops) {
>>> + /*
>>> + * Initialize the ICC even if BPMP-FW doesn't support
>>> 'MRQ_BWMGR_INT'.
>>> + * Use the flag 'mc->bwmgr_mrq_supported' within MC
>>> driver and return
>>> + * EINVAL instead of passing the request to BPMP-FW
>>> later when the BW
>>> + * request is made by client with 'icc_set_bw()' call.
>>> + */
>>> + err = tegra_emc_interconnect_init(emc);
>>> + if (err)
>>> + goto put_bpmp;
>>> +
>>> + if (tegra_bpmp_mrq_is_supported(emc->bpmp,
>>> MRQ_BWMGR_INT)) {
>>> + mc->bwmgr_mrq_supported = true;
>>> +
>>> + /*
>>> + * MC driver probe can't get BPMP reference as
>>> it gets probed
>>> + * earlier than BPMP. So, save the BPMP ref got
>>> from the EMC
>>> + * DT node in the mc->bpmp and use it in MC's
>>> icc_set hook.
>>> + */
>>> + mc->bpmp = emc->bpmp;
>>
>> This (and ()) are called without any locking. You register first the
>> interconnect, so set() callback can be used, right? Then set() could be
>> called anytime between tegra_emc_interconnect_init() and assignment
>> above. How do you synchronize these?
>>
>> Best regards,
>> Krzysztof
>>
>
> Currently, the tegra234_mc_icc_set() has NULL check. So, it will give
> this error.
> if (!mc->bpmp) {
> dev_err(mc->dev, "BPMP reference NULL\n");
> return -ENOENT;
> }
>
> To fix, we can do the below change and swap the order. Please let me
> know if this sounds fine ?
> if (mc && mc->soc->icc_ops) {
> if (tegra_bpmp_mrq_is_supported(emc->bpmp, MRQ_BWMGR_INT)) {
> mc->bwmgr_mrq_supported = true;
> mc->bpmp = emc->bpmp;
> }
>
> err = tegra_emc_interconnect_init(emc);
> if (err)
> goto put_bpmp;
>
> }
Sorry, replied too soon. Missed setting "mc->bpmp" to NULL. Sharing new
proposed change. Please let me know if this looks OK.
if (mc && mc->soc->icc_ops) {
if (tegra_bpmp_mrq_is_supported(emc->bpmp, MRQ_BWMGR_INT)) {
mc->bwmgr_mrq_supported = true;
mc->bpmp = emc->bpmp;
}
err = tegra_emc_interconnect_init(emc);
if (err) {
mc->bpmp = NULL;
goto put_bpmp;
}
}
>
> Thank you,
> Sumit Gupta
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