1 files changed, 191 insertions, 46 deletions

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 6730f965b..8adac69db 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -39,6 +39,7 @@
 
 #include <linux/cpufreq.h>
 #include <linux/delay.h>
+#include <linux/ktime.h>
 
 #include <acpi/cppc_acpi.h>
 /*
@@ -63,58 +64,140 @@ static struct mbox_chan *pcc_channel;
 static void __iomem *pcc_comm_addr;
 static u64 comm_base_addr;
 static int pcc_subspace_idx = -1;
-static u16 pcc_cmd_delay;
 static bool pcc_channel_acquired;
+static ktime_t deadline;
+static unsigned int pcc_mpar, pcc_mrtt;
+
+/* pcc mapped address + header size + offset within PCC subspace */
+#define GET_PCC_VADDR(offs) (pcc_comm_addr + 0x8 + (offs))
 
 /*
  * Arbitrary Retries in case the remote processor is slow to respond
- * to PCC commands.
+ * to PCC commands. Keeping it high enough to cover emulators where
+ * the processors run painfully slow.
  */
 #define NUM_RETRIES 500
 
+static int check_pcc_chan(void)
+{
+	int ret = -EIO;
+	struct acpi_pcct_shared_memory __iomem *generic_comm_base = pcc_comm_addr;
+	ktime_t next_deadline = ktime_add(ktime_get(), deadline);
+
+	/* Retry in case the remote processor was too slow to catch up. */
+	while (!ktime_after(ktime_get(), next_deadline)) {
+		/*
+		 * Per spec, prior to boot the PCC space wil be initialized by
+		 * platform and should have set the command completion bit when
+		 * PCC can be used by OSPM
+		 */
+		if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) {
+			ret = 0;
+			break;
+		}
+		/*
+		 * Reducing the bus traffic in case this loop takes longer than
+		 * a few retries.
+		 */
+		udelay(3);
+	}
+
+	return ret;
+}
+
 static int send_pcc_cmd(u16 cmd)
 {
-	int retries, result = -EIO;
-	struct acpi_pcct_hw_reduced *pcct_ss = pcc_channel->con_priv;
+	int ret = -EIO;
 	struct acpi_pcct_shared_memory *generic_comm_base =
 		(struct acpi_pcct_shared_memory *) pcc_comm_addr;
-	u32 cmd_latency = pcct_ss->latency;
+	static ktime_t last_cmd_cmpl_time, last_mpar_reset;
+	static int mpar_count;
+	unsigned int time_delta;
 
-	/* Min time OS should wait before sending next command. */
-	udelay(pcc_cmd_delay);
+	/*
+	 * For CMD_WRITE we know for a fact the caller should have checked
+	 * the channel before writing to PCC space
+	 */
+	if (cmd == CMD_READ) {
+		ret = check_pcc_chan();
+		if (ret)
+			return ret;
+	}
+
+	/*
+	 * Handle the Minimum Request Turnaround Time(MRTT)
+	 * "The minimum amount of time that OSPM must wait after the completion
+	 * of a command before issuing the next command, in microseconds"
+	 */
+	if (pcc_mrtt) {
+		time_delta = ktime_us_delta(ktime_get(), last_cmd_cmpl_time);
+		if (pcc_mrtt > time_delta)
+			udelay(pcc_mrtt - time_delta);
+	}
+
+	/*
+	 * Handle the non-zero Maximum Periodic Access Rate(MPAR)
+	 * "The maximum number of periodic requests that the subspace channel can
+	 * support, reported in commands per minute. 0 indicates no limitation."
+	 *
+	 * This parameter should be ideally zero or large enough so that it can
+	 * handle maximum number of requests that all the cores in the system can
+	 * collectively generate. If it is not, we will follow the spec and just
+	 * not send the request to the platform after hitting the MPAR limit in
+	 * any 60s window
+	 */
+	if (pcc_mpar) {
+		if (mpar_count == 0) {
+			time_delta = ktime_ms_delta(ktime_get(), last_mpar_reset);
+			if (time_delta < 60 * MSEC_PER_SEC) {
+				pr_debug("PCC cmd not sent due to MPAR limit");
+				return -EIO;
+			}
+			last_mpar_reset = ktime_get();
+			mpar_count = pcc_mpar;
+		}
+		mpar_count--;
+	}
 
 	/* Write to the shared comm region. */
-	writew(cmd, &generic_comm_base->command);
+	writew_relaxed(cmd, &generic_comm_base->command);
 
 	/* Flip CMD COMPLETE bit */
-	writew(0, &generic_comm_base->status);
+	writew_relaxed(0, &generic_comm_base->status);
 
 	/* Ring doorbell */
-	result = mbox_send_message(pcc_channel, &cmd);
-	if (result < 0) {
+	ret = mbox_send_message(pcc_channel, &cmd);
+	if (ret < 0) {
 		pr_err("Err sending PCC mbox message. cmd:%d, ret:%d\n",
-				cmd, result);
-		return result;
+				cmd, ret);
+		return ret;
 	}
 
-	/* Wait for a nominal time to let platform process command. */
-	udelay(cmd_latency);
-
-	/* Retry in case the remote processor was too slow to catch up. */
-	for (retries = NUM_RETRIES; retries > 0; retries--) {
-		if (readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE) {
-			result = 0;
-			break;
-		}
+	/*
+	 * For READs we need to ensure the cmd completed to ensure
+	 * the ensuing read()s can proceed. For WRITEs we dont care
+	 * because the actual write()s are done before coming here
+	 * and the next READ or WRITE will check if the channel
+	 * is busy/free at the entry of this call.
+	 *
+	 * If Minimum Request Turnaround Time is non-zero, we need
+	 * to record the completion time of both READ and WRITE
+	 * command for proper handling of MRTT, so we need to check
+	 * for pcc_mrtt in addition to CMD_READ
+	 */
+	if (cmd == CMD_READ || pcc_mrtt) {
+		ret = check_pcc_chan();
+		if (pcc_mrtt)
+			last_cmd_cmpl_time = ktime_get();
 	}
 
-	mbox_client_txdone(pcc_channel, result);
-	return result;
+	mbox_client_txdone(pcc_channel, ret);
+	return ret;
 }
 
 static void cppc_chan_tx_done(struct mbox_client *cl, void *msg, int ret)
 {
-	if (ret)
+	if (ret < 0)
 		pr_debug("TX did not complete: CMD sent:%x, ret:%d\n",
 				*(u16 *)msg, ret);
 	else
@@ -306,6 +389,7 @@ static int register_pcc_channel(int pcc_subspace_idx)
 {
 	struct acpi_pcct_hw_reduced *cppc_ss;
 	unsigned int len;
+	u64 usecs_lat;
 
 	if (pcc_subspace_idx >= 0) {
 		pcc_channel = pcc_mbox_request_channel(&cppc_mbox_cl,
@@ -335,7 +419,16 @@ static int register_pcc_channel(int pcc_subspace_idx)
 		 */
 		comm_base_addr = cppc_ss->base_address;
 		len = cppc_ss->length;
-		pcc_cmd_delay = cppc_ss->min_turnaround_time;
+
+		/*
+		 * cppc_ss->latency is just a Nominal value. In reality
+		 * the remote processor could be much slower to reply.
+		 * So add an arbitrary amount of wait on top of Nominal.
+		 */
+		usecs_lat = NUM_RETRIES * cppc_ss->latency;
+		deadline = ns_to_ktime(usecs_lat * NSEC_PER_USEC);
+		pcc_mrtt = cppc_ss->min_turnaround_time;
+		pcc_mpar = cppc_ss->max_access_rate;
 
 		pcc_comm_addr = acpi_os_ioremap(comm_base_addr, len);
 		if (!pcc_comm_addr) {
@@ -546,29 +639,74 @@ void acpi_cppc_processor_exit(struct acpi_processor *pr)
 }
 EXPORT_SYMBOL_GPL(acpi_cppc_processor_exit);
 
-static u64 get_phys_addr(struct cpc_reg *reg)
-{
-	/* PCC communication addr space begins at byte offset 0x8. */
-	if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM)
-		return (u64)comm_base_addr + 0x8 + reg->address;
-	else
-		return reg->address;
-}
+/*
+ * Since cpc_read and cpc_write are called while holding pcc_lock, it should be
+ * as fast as possible. We have already mapped the PCC subspace during init, so
+ * we can directly write to it.
+ */
 
-static void cpc_read(struct cpc_reg *reg, u64 *val)
+static int cpc_read(struct cpc_reg *reg, u64 *val)
 {
-	u64 addr = get_phys_addr(reg);
+	int ret_val = 0;
 
-	acpi_os_read_memory((acpi_physical_address)addr,
-			val, reg->bit_width);
+	*val = 0;
+	if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
+		void __iomem *vaddr = GET_PCC_VADDR(reg->address);
+
+		switch (reg->bit_width) {
+		case 8:
+			*val = readb_relaxed(vaddr);
+			break;
+		case 16:
+			*val = readw_relaxed(vaddr);
+			break;
+		case 32:
+			*val = readl_relaxed(vaddr);
+			break;
+		case 64:
+			*val = readq_relaxed(vaddr);
+			break;
+		default:
+			pr_debug("Error: Cannot read %u bit width from PCC\n",
+				reg->bit_width);
+			ret_val = -EFAULT;
+		}
+	} else
+		ret_val = acpi_os_read_memory((acpi_physical_address)reg->address,
+					val, reg->bit_width);
+	return ret_val;
 }
 
-static void cpc_write(struct cpc_reg *reg, u64 val)
+static int cpc_write(struct cpc_reg *reg, u64 val)
 {
-	u64 addr = get_phys_addr(reg);
+	int ret_val = 0;
 
-	acpi_os_write_memory((acpi_physical_address)addr,
-			val, reg->bit_width);
+	if (reg->space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
+		void __iomem *vaddr = GET_PCC_VADDR(reg->address);
+
+		switch (reg->bit_width) {
+		case 8:
+			writeb_relaxed(val, vaddr);
+			break;
+		case 16:
+			writew_relaxed(val, vaddr);
+			break;
+		case 32:
+			writel_relaxed(val, vaddr);
+			break;
+		case 64:
+			writeq_relaxed(val, vaddr);
+			break;
+		default:
+			pr_debug("Error: Cannot write %u bit width to PCC\n",
+				reg->bit_width);
+			ret_val = -EFAULT;
+			break;
+		}
+	} else
+		ret_val = acpi_os_write_memory((acpi_physical_address)reg->address,
+				val, reg->bit_width);
+	return ret_val;
 }
 
 /**
@@ -604,7 +742,7 @@ int cppc_get_perf_caps(int cpunum, struct cppc_perf_caps *perf_caps)
 			(ref_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
 			(nom_perf->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) {
 		/* Ring doorbell once to update PCC subspace */
-		if (send_pcc_cmd(CMD_READ)) {
+		if (send_pcc_cmd(CMD_READ) < 0) {
 			ret = -EIO;
 			goto out_err;
 		}
@@ -662,7 +800,7 @@ int cppc_get_perf_ctrs(int cpunum, struct cppc_perf_fb_ctrs *perf_fb_ctrs)
 	if ((delivered_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) ||
 			(reference_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM)) {
 		/* Ring doorbell once to update PCC subspace */
-		if (send_pcc_cmd(CMD_READ)) {
+		if (send_pcc_cmd(CMD_READ) < 0) {
 			ret = -EIO;
 			goto out_err;
 		}
@@ -713,6 +851,13 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
 
 	spin_lock(&pcc_lock);
 
+	/* If this is PCC reg, check if channel is free before writing */
+	if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
+		ret = check_pcc_chan();
+		if (ret)
+			goto busy_channel;
+	}
+
 	/*
 	 * Skip writing MIN/MAX until Linux knows how to come up with
 	 * useful values.
@@ -722,10 +867,10 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
 	/* Is this a PCC reg ?*/
 	if (desired_reg->cpc_entry.reg.space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
 		/* Ring doorbell so Remote can get our perf request. */
-		if (send_pcc_cmd(CMD_WRITE))
+		if (send_pcc_cmd(CMD_WRITE) < 0)
 			ret = -EIO;
 	}
-
+busy_channel:
 	spin_unlock(&pcc_lock);
 
 	return ret;