memory: tegra30: Support interconnect framework

Now Internal and External memory controllers are memory interconnection
providers. This allows us to use interconnect API for tuning of memory
configuration. EMC driver now supports OPPs and DVFS. MC driver now
supports tuning of memory arbitration latency, which needs to be done
for ISO memory clients, like a Display client for example.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Peter Geis <pgwipeout@gmail.com>
Acked-by: Georgi Djakov <georgi.djakov@linaro.org>
Acked-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20201203192439.16177-4-digetx@gmail.comSigned-off-by: Krzysztof Kozlowski <krzk@kernel.org>

drivers/memory/tegra/Kconfig

@@ -24,6 +24,7 @@ config TEGRA30_EMC
 	tristate "NVIDIA Tegra30 External Memory Controller driver"
 	default y
 	depends on TEGRA_MC && ARCH_TEGRA_3x_SOC
+	select PM_OPP
 	help
 	  This driver is for the External Memory Controller (EMC) found on
 	  Tegra30 chips. The EMC controls the external DRAM on the board.

drivers/memory/tegra/tegra30.c

@@ -4,7 +4,8 @@
  */
 
 #include <linux/of.h>
-#include <linux/mm.h>
+#include <linux/of_device.h>
+#include <linux/slab.h>
 
 #include <dt-bindings/memory/tegra30-mc.h>
 
@@ -1083,6 +1084,175 @@ static const struct tegra_mc_reset tegra30_mc_resets[] = {
 	TEGRA30_MC_RESET(VI,       0x200, 0x204, 17),
 };
 
+static void tegra30_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;
+	const struct tegra_mc_la *la = &client->la;
+	unsigned int fifo_size = client->fifo_size;
+	u32 arb_nsec, la_ticks, value;
+
+	/* see 18.4.1 Client Configuration in Tegra3 TRM v03p */
+	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, la->mask);
+
+	value = mc_readl(mc, la->reg);
+	value &= ~(la->mask << la->shift);
+	value |= la_ticks << la->shift;
+	mc_writel(mc, value, la->reg);
+}
+
+static int tegra30_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);
+
+	tegra30_mc_tune_client_latency(mc, client, peak_bandwidth);
+
+	return 0;
+}
+
+static int tegra30_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 *
+tegra30_mc_of_icc_xlate_extended(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 tegra30_mc_icc_ops = {
+	.xlate_extended = tegra30_mc_of_icc_xlate_extended,
+	.aggregate = tegra30_mc_icc_aggreate,
+	.set = tegra30_mc_icc_set,
+};
+
 const struct tegra_mc_soc tegra30_mc_soc = {
 	.clients = tegra30_mc_clients,
 	.num_clients = ARRAY_SIZE(tegra30_mc_clients),
@@ -1097,4 +1267,5 @@ const struct tegra_mc_soc tegra30_mc_soc = {
 	.reset_ops = &tegra_mc_reset_ops_common,
 	.resets = tegra30_mc_resets,
 	.num_resets = ARRAY_SIZE(tegra30_mc_resets),
+	.icc_ops = &tegra30_mc_icc_ops,
 };