[PATCH v3 04/11] memory: tegra: implement EMEM regs and ICC ops for Tegra114

Svyatoslav Ryhel
2025-09-15T08:02:29Z

Prepare Internal Memory Controller for introduction of External Memory
Controller.

Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
---
drivers/memory/tegra/tegra114.c | 193 ++++++++++++++++++++++++++++++++
1 file changed, 193 insertions(+)

diff --git a/drivers/memory/tegra/tegra114.c b/drivers/memory/tegra/tegra114.c
index d03a5d162dbd..c615857f7fad 100644
--- a/drivers/memory/tegra/tegra114.c
+++ b/drivers/memory/tegra/tegra114.c
@@ -3,6 +3,7 @@
* Copyright (C) 2014 NVIDIA CORPORATION. All rights reserved.
*/

+#include <linux/device.h>
#include <linux/of.h>
#include <linux/mm.h>

@@ -1165,6 +1166,195 @@ static const struct tegra_mc_reset tegra114_mc_resets[] = {
TEGRA114_MC_RESET(VI, 0x200, 0x204, 17),
};

+static void tegra114_mc_tune_client_latency(struct tegra_mc *mc,
+ const struct tegra_mc_client *client,
+ unsigned int bandwidth_mbytes_sec)
+{
+ u32 arb_tolerance_compensation_nsec, arb_tolerance_compensation_div;
+ unsigned int fifo_size = client->fifo_size;
+ u32 arb_nsec, la_ticks, value;
+
+ /* see 20.3.1.1 Client Configuration in Tegra4 TRM v01p */
+ if (bandwidth_mbytes_sec)
+ arb_nsec = fifo_size * NSEC_PER_USEC / bandwidth_mbytes_sec;
+ else
+ arb_nsec = U32_MAX;
+
+ /*
+ * Latency allowness should be set with consideration for the module's
+ * latency tolerance and internal buffering capabilities.
+ *
+ * Display memory clients use isochronous transfers and have very low
+ * tolerance to a belated transfers. Hence we need to compensate the
+ * memory arbitration imperfection for them in order to prevent FIFO
+ * underflow condition when memory bus is busy.
+ *
+ * VI clients also need a stronger compensation.
+ */
+ switch (client->swgroup) {
+ case TEGRA_SWGROUP_MPCORE:
+ case TEGRA_SWGROUP_PTC:
+ /*
+ * We always want lower latency for these clients, hence
+ * don't touch them.
+ */
+ return;
+
+ case TEGRA_SWGROUP_DC:
+ case TEGRA_SWGROUP_DCB:
+ arb_tolerance_compensation_nsec = 1050;
+ arb_tolerance_compensation_div = 2;
+ break;
+
+ case TEGRA_SWGROUP_VI:
+ arb_tolerance_compensation_nsec = 1050;
+ arb_tolerance_compensation_div = 1;
+ break;
+
+ default:
+ arb_tolerance_compensation_nsec = 150;
+ arb_tolerance_compensation_div = 1;
+ break;
+ }
+
+ if (arb_nsec > arb_tolerance_compensation_nsec)
+ arb_nsec -= arb_tolerance_compensation_nsec;
+ else
+ arb_nsec = 0;
+
+ arb_nsec /= arb_tolerance_compensation_div;
+
+ /*
+ * Latency allowance is a number of ticks a request from a particular
+ * client may wait in the EMEM arbiter before it becomes a high-priority
+ * request.
+ */
+ la_ticks = arb_nsec / mc->tick;
+ la_ticks = min(la_ticks, client->regs.la.mask);
+
+ value = mc_readl(mc, client->regs.la.reg);
+ value &= ~(client->regs.la.mask << client->regs.la.shift);
+ value |= la_ticks << client->regs.la.shift;
+ mc_writel(mc, value, client->regs.la.reg);
+}
+
+static int tegra114_mc_icc_set(struct icc_node *src, struct icc_node *dst)
+{
+ struct tegra_mc *mc = icc_provider_to_tegra_mc(src->provider);
+ const struct tegra_mc_client *client = &mc->soc->clients[src->id];
+ u64 peak_bandwidth = icc_units_to_bps(src->peak_bw);
+
+ /*
+ * Skip pre-initialization that is done by icc_node_add(), which sets
+ * bandwidth to maximum for all clients before drivers are loaded.
+ *
+ * This doesn't make sense for us because we don't have drivers for all
+ * clients and it's okay to keep configuration left from bootloader
+ * during boot, at least for today.
+ */
+ if (src == dst)
+ return 0;
+
+ /* convert bytes/sec to megabytes/sec */
+ do_div(peak_bandwidth, 1000000);
+
+ tegra114_mc_tune_client_latency(mc, client, peak_bandwidth);
+
+ return 0;
+}
+
+static int tegra114_mc_icc_aggreate(struct icc_node *node, u32 tag, u32 avg_bw,
+ u32 peak_bw, u32 *agg_avg, u32 *agg_peak)
+{
+ /*
+ * ISO clients need to reserve extra bandwidth up-front because
+ * there could be high bandwidth pressure during initial filling
+ * of the client's FIFO buffers. Secondly, we need to take into
+ * account impurities of the memory subsystem.
+ */
+ if (tag & TEGRA_MC_ICC_TAG_ISO)
+ peak_bw = tegra_mc_scale_percents(peak_bw, 400);
+
+ *agg_avg += avg_bw;
+ *agg_peak = max(*agg_peak, peak_bw);
+
+ return 0;
+}
+
+static struct icc_node_data *
+tegra114_mc_of_icc_xlate_extended(const struct of_phandle_args *spec, void *data)
+{
+ struct tegra_mc *mc = icc_provider_to_tegra_mc(data);
+ const struct tegra_mc_client *client;
+ unsigned int i, idx = spec->args[0];
+ struct icc_node_data *ndata;
+ struct icc_node *node;
+
+ list_for_each_entry(node, &mc->provider.nodes, node_list) {
+ if (node->id != idx)
+ continue;
+
+ ndata = kzalloc(sizeof(*ndata), GFP_KERNEL);
+ if (!ndata)
+ return ERR_PTR(-ENOMEM);
+
+ client = &mc->soc->clients[idx];
+ ndata->node = node;
+
+ switch (client->swgroup) {
+ case TEGRA_SWGROUP_DC:
+ case TEGRA_SWGROUP_DCB:
+ case TEGRA_SWGROUP_PTC:
+ case TEGRA_SWGROUP_VI:
+ /* these clients are isochronous by default */
+ ndata->tag = TEGRA_MC_ICC_TAG_ISO;
+ break;
+
+ default:
+ ndata->tag = TEGRA_MC_ICC_TAG_DEFAULT;
+ break;
+ }
+
+ return ndata;
+ }
+
+ for (i = 0; i < mc->soc->num_clients; i++) {
+ if (mc->soc->clients[i].id == idx)
+ return ERR_PTR(-EPROBE_DEFER);
+ }
+
+ dev_err(mc->dev, "invalid ICC client ID %u\n", idx);
+
+ return ERR_PTR(-EINVAL);
+}
+
+static const struct tegra_mc_icc_ops tegra114_mc_icc_ops = {
+ .xlate_extended = tegra114_mc_of_icc_xlate_extended,
+ .aggregate = tegra114_mc_icc_aggreate,
+ .set = tegra114_mc_icc_set,
+};
+
+static const unsigned long tegra114_mc_emem_regs[] = {
+ MC_EMEM_ARB_CFG,
+ MC_EMEM_ARB_OUTSTANDING_REQ,
+ MC_EMEM_ARB_TIMING_RCD,
+ MC_EMEM_ARB_TIMING_RP,
+ MC_EMEM_ARB_TIMING_RC,
+ MC_EMEM_ARB_TIMING_RAS,
+ MC_EMEM_ARB_TIMING_FAW,
+ MC_EMEM_ARB_TIMING_RRD,
+ MC_EMEM_ARB_TIMING_RAP2PRE,
+ MC_EMEM_ARB_TIMING_WAP2PRE,
+ MC_EMEM_ARB_TIMING_R2R,
+ MC_EMEM_ARB_TIMING_W2W,
+ MC_EMEM_ARB_TIMING_R2W,
+ MC_EMEM_ARB_TIMING_W2R,
+ MC_EMEM_ARB_DA_TURNS,
+ MC_EMEM_ARB_DA_COVERS,
+ MC_EMEM_ARB_MISC0,
+ MC_EMEM_ARB_RING1_THROTTLE,
+};
+
const struct tegra_mc_soc tegra114_mc_soc = {
.clients = tegra114_mc_clients,
.num_clients = ARRAY_SIZE(tegra114_mc_clients),
@@ -1172,10 +1362,13 @@ const struct tegra_mc_soc tegra114_mc_soc = {
.atom_size = 32,
.client_id_mask = 0x7f,
.smmu = &tegra114_smmu_soc,
+ .emem_regs = tegra114_mc_emem_regs,
+ .num_emem_regs = ARRAY_SIZE(tegra114_mc_emem_regs),
.intmask = MC_INT_INVALID_SMMU_PAGE | MC_INT_SECURITY_VIOLATION |
MC_INT_DECERR_EMEM,
.reset_ops = &tegra_mc_reset_ops_common,
.resets = tegra114_mc_resets,
.num_resets = ARRAY_SIZE(tegra114_mc_resets),
+ .icc_ops = &tegra114_mc_icc_ops,
.ops = &tegra30_mc_ops,
};
--
2.48.1