interconnect: qcom: add MSM8x60 (MSM8660/APQ8060) NoC driver

Add a Qualcomm interconnect driver for the MSM8x60 family modelling the four NoC fabrics (APPSS, System, MMSS, DFAB) that connect masters and slaves on these Scorpion-class SoCs. The driver implements the interconnect-provider API to manage bandwidth between specific masters and slaves via the RPM arbitration tables.

Each fabric carries:
- A bus clock (managed via clk_bulk APIs) whose rate is the aggregated bandwidth divided by the fabric bus width, with a minimum floor of 384 MHz to prevent USB starvation observed when the fabric drops to the previously-used 266 MHz minimum.
- An RPM arbitration buffer (arb / bwsum) that the RPM firmware consumes via its shared-memory protocol; commits go via the qcom-rpm driver's set_resource API.

msm8660_get_rpm() pins the supplier with device_link_add() before reading drvdata so an unbind/rebind window cannot leave a stale qcom_rpm pointer. clk_bulk_prepare_enable is paired with a devm_add_action_or_reset cleanup so an EPROBE_DEFER from the RPM lookup does not leak the prepare/enable refcount across retries. The fabric rate cap uses min_t(u64,...) so a bandwidth request exceeding 4 GiB/s cannot wrap through u32 truncation into a near-zero clock rate that would halt the interconnect.

Signed-off-by Herman van Hazendonk <[email protected]>

---
 drivers/interconnect/qcom/Kconfig             |   14 +
 drivers/interconnect/qcom/Makefile            |    2 +
 drivers/interconnect/qcom/msm8660.c           | 1147 +++++++++++++++++
 .../dt-bindings/interconnect/qcom,msm8660.h   |    6 +-
 4 files changed, 1166 insertions(+), 3 deletions(-)
 create mode 100644 drivers/interconnect/qcom/msm8660.c

drivers/interconnect/qcom/msm8660.c new file +12 -0

+
+/*
+ * RPM fabric arbitration data format (from legacy vendor kernel msm_bus_fabric.c):
+ *
+ * Each u16 arb entry: bit 15 = tier (1=TIER1 high priority), bits 14-0 = BW
+ * Bandwidth is in 128KB units (bytes >> 17).
+ * Two u16 values are packed into each u32 RPM register word.
+ *
+ * Buffer layout: [bwsum pairs] [arb pairs]
+ * bwsum[slave_port] = total bandwidth to that slave
+ * arb[(tier-1)*nmasters + master_port] = per-master arbitration entry
+ */

drivers/interconnect/qcom/msm8660.c new file +11 -0

+	static struct msm8660_icc_node _name = {			\
+		.name = #_name,						\
+		.id = _id,						\
+		.buswidth = _buswidth,					\
+		.num_links = COUNT_ARGS(__VA_ARGS__),			\
+		.links = { __VA_ARGS__ },				\
+		.mas_port = _mas,					\
+		.slv_port = _slv,					\
+		.mas_tier = _tier,					\
+	}
+

drivers/interconnect/qcom/msm8660.c new file +18 -0

+/*
+ * Look up the RPM that owns fabric arbitration writes.
+ *
+ * Returns NULL if the DT does not have a "qcom,rpm" phandle (in which
+ * case the caller silently drops RPM ARB and runs the fabric purely
+ * via clk_set_rate).
+ *
+ * Returns ERR_PTR(-EPROBE_DEFER) if the RPM device exists in DT but
+ * its driver has not finished probing yet, or if device_link_add()
+ * fails. The caller is expected to propagate this so the interconnect
+ * driver gets retried once the RPM is ready.
+ *
+ * On success returns the qcom_rpm handle and pins the RPM device
+ * lifetime to ours via a consumer-supplier device link, so the
+ * devres-allocated qcom_rpm cannot be freed while we still hold a
+ * pointer to it.
+ */
+static struct qcom_rpm *msm8660_get_rpm(struct device *dev)

drivers/interconnect/qcom/msm8660.c new file +76 -0

+	}
+
+	rpm_pdev = of_find_device_by_node(rpm_np);
+	of_node_put(rpm_np);
+	if (!rpm_pdev) {
+		dev_dbg(dev, "RPM device not found yet, deferring probe\n");
+		return ERR_PTR(-EPROBE_DEFER);
+	}
+
+	/*
+	 * Pin the supplier BEFORE reading its drvdata. The device link
+	 * (MANAGED, the default state) prevents the RPM driver from being
+	 * unbound while we hold the link, which closes the window where a
+	 * concurrent unbind+rebind could free the qcom_rpm pointer between
+	 * dev_get_drvdata() and the link being established. If the link
+	 * cannot be added (e.g. supplier is in the process of being
+	 * removed) we defer and retry.
+	 */
+	link = device_link_add(dev, &rpm_pdev->dev,
+			       DL_FLAG_AUTOREMOVE_CONSUMER);
+	put_device(&rpm_pdev->dev);
+	if (!link) {
+		dev_warn(dev, "failed to add device link to RPM, deferring\n");
+		return ERR_PTR(-EPROBE_DEFER);
+	}
+
+	/*
+	 * Safe to read drvdata now: the device link pins the supplier so
+	 * it cannot be unbound until our consumer (this interconnect
+	 * provider) is unbound first.
+	 */
+	rpm = dev_get_drvdata(&rpm_pdev->dev);
+	if (!rpm) {
+		dev_dbg(dev, "RPM not ready, deferring probe\n");
+		device_link_remove(dev, &rpm_pdev->dev);
+		return ERR_PTR(-EPROBE_DEFER);
+	}
+
+	return rpm;
+}
+
+static int msm8660_icc_probe(struct platform_device *pdev)
+{
+	const struct msm8660_icc_desc *desc;
+	struct msm8660_icc_node * const *qnodes;
+	struct msm8660_icc_provider *qp;
+	struct device *dev = &pdev->dev;
+	struct icc_onecell_data *data;
+	struct icc_provider *provider;
+	struct icc_node *node;
+	size_t num_nodes, i;
+	int ret;
+
+	desc = of_device_get_match_data(dev);
+	if (!desc)
+		return -EINVAL;
+
+	qnodes = desc->nodes;
+	num_nodes = desc->num_nodes;
+
+	qp = devm_kzalloc(dev, sizeof(*qp), GFP_KERNEL);
+	if (!qp)
+		return -ENOMEM;
+
+	data = devm_kzalloc(dev, struct_size(data, nodes, num_nodes),
+			    GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+	data->num_nodes = num_nodes;
+
+	qp->bus_clks = devm_kmemdup(dev, desc->bus_clks,
+				    desc->num_clks * sizeof(*desc->bus_clks),
+				    GFP_KERNEL);
+	if (!qp->bus_clks)
+		return -ENOMEM;
+

drivers/interconnect/qcom/msm8660.c new file +89 -0

+	 */
+	ret = devm_clk_bulk_get_optional(dev, qp->num_clks, qp->bus_clks);
+	if (ret == -EPROBE_DEFER)
+		return ret;
+	if (ret) {
+		dev_warn(dev, "Failed to get bus clocks: %d (continuing without clock scaling)\n",
+			 ret);
+		qp->num_clks = 0;
+	}
+
+	if (qp->num_clks) {
+		ret = clk_bulk_prepare_enable(qp->num_clks, qp->bus_clks);
+		if (ret) {
+			dev_warn(dev, "Failed to enable bus clocks: %d\n", ret);
+			qp->num_clks = 0;
+		} else {
+			/*
+			 * Register the cleanup right after a successful
+			 * prepare_enable so any later -EPROBE_DEFER or other
+			 * probe error path (e.g. msm8660_get_rpm failing
+			 * with -EPROBE_DEFER below) does not leak a clock
+			 * prepare/enable reference across the retry.
+			 */
+			ret = devm_add_action_or_reset(dev,
+				msm8660_icc_clk_release, qp);
+			if (ret)
+				return ret;
+		}
+	}
+
+	/* Set up RPM fabric arbitration */
+	qp->desc = desc;
+	if (desc->rpm_resource >= 0) {
+		qp->rpm = msm8660_get_rpm(dev);
+		if (IS_ERR(qp->rpm))
+			return PTR_ERR(qp->rpm);
+		if (qp->rpm) {
+			int arb_size = desc->nmasters * desc->ntieredslaves;
+
+			qp->bwsum = devm_kcalloc(dev, desc->nslaves,
+						 sizeof(u16), GFP_KERNEL);
+			qp->arb = devm_kcalloc(dev, arb_size,
+					       sizeof(u16), GFP_KERNEL);
+			qp->rpm_buf = devm_kcalloc(dev, desc->rpm_buf_size,
+						   sizeof(u32), GFP_KERNEL);
+			if (!qp->bwsum || !qp->arb || !qp->rpm_buf) {
+				dev_warn(dev, "RPM buffer alloc failed, ARB disabled\n");
+				qp->rpm = NULL;
+			} else {
+				int rc;
+
+				dev_info(dev, "RPM fabric ARB enabled (%d masters, %d slaves, %d tiered)\n",
+					 desc->nmasters, desc->nslaves,
+					 desc->ntieredslaves);
+
+				/*
+				 * One-shot sleep-context vote of zero bandwidth.
+				 * Without an explicit SLEEP_STATE write, RPM has no
+				 * fabric bandwidth target for deep-sleep and may
+				 * keep the active vote applied indefinitely,
+				 * preventing DDR from dropping its rate when CPUs
+				 * power-collapse. The buffer is devm_kcalloc'd so
+				 * it is all-zero at this point — written before
+				 * any consumer can drive an active vote that would
+				 * dirty it.
+				 *
+				 * msm8660_rpm_commit() writes ACTIVE_STATE only;
+				 * SLEEP_STATE remains zero for the provider's
+				 * lifetime, so this vote does not need refreshing.
+				 */
+				rc = qcom_rpm_write(qp->rpm,
+						    QCOM_RPM_SLEEP_STATE,
+						    desc->rpm_resource,
+						    qp->rpm_buf,
+						    desc->rpm_buf_size);
+				if (rc)
+					dev_warn(dev, "RPM fabric sleep vote failed: %d\n",
+						 rc);
+			}
+		}
+	}
+
+	provider = &qp->provider;
+	provider->dev = dev;
+	provider->set = msm8660_icc_set;
+	provider->aggregate = msm8660_icc_aggregate;
+	provider->xlate = of_icc_xlate_onecell;
+	provider->data = data;
+	provider->get_bw = msm8660_get_bw;

drivers/interconnect/qcom/msm8660.c new file +9 -0

+		if (IS_ERR(node)) {
+			ret = PTR_ERR(node);
+			goto err_remove_nodes;
+		}
+
+		node->name = qnodes[i]->name;
+		node->data = qnodes[i];
+		icc_node_add(node, provider);
+

Add interconnect support for the MSM8x60 family (MSM8260, MSM8660, APQ8060) — Qualcomm's Scorpion dual-core SoC generation used in devices like the HP TouchPad, HTC EVO 3D and HTC Sensation.

The chip's Network-on-Chip fabric is divided into four sub-fabrics:

AFAB - Applications fabric: Scorpion CPU + L2 cache, paths to EBI SFAB - System fabric: DMA engines, SPS, USB HS, LPASS, MSS MMFAB - Multimedia fabric: MDP, GPU, camera (VFE/JPEG), video codec DFAB - Daytona fabric: eMMC/SD (SDC), ADM DMA, USB voter

Bandwidth requests are committed to the RPM firmware via its shared-memory arbitration tables using the qcom-rpm driver backend; each fabric also has a bus clock whose rate is derived from the aggregated bandwidth.

The driver includes a 384 MHz bus clock floor, replacing the previous 266 MHz minimum that caused USB starvation on real hardware, and careful devm/device_link lifecycle to handle EPROBE_DEFER from both RPM and clock lookups without leaking clock prepare/enable references.

Signed-off-by Herman van Hazendonk <[email protected]>

Herman van Hazendonk (2):
dt-bindings: interconnect: qcom: add msm8660 fabric IDs
interconnect: qcom: add MSM8x60 NoC driver

  drivers/interconnect/qcom/Kconfig             |   14 +
  drivers/interconnect/qcom/Makefile            |    2 +
  drivers/interconnect/qcom/msm8660.c           | 1147 +++++++++++++++++
  .../dt-bindings/interconnect/qcom,msm8660.h   |  156 +++
  4 files changed, 1319 insertions(+)

create mode 100644 drivers/interconnect/qcom/msm8660.c create mode 100644 include/dt-bindings/interconnect/qcom,msm8660.h

base-commit: 944125b4c454b58d2fe6e35f1087a932b2050dff