Re: [PATCH v4 2/2] ACPI / CPPC: Make cppc acpi driver aware of pcc subspace ids

George Cherian <gcherian@xxxxxxxxxxxxxxxxxx> · Tue, 3 Oct 2017 16:31:35 +0530

Hi Prakash,

On 09/29/2017 04:49 AM, Prakash, Prashanth wrote:
Hi George,

On 9/19/2017 11:24 PM, George Cherian wrote:
Based on ACPI 6.2 Section 8.4.7.1.9 If the PCC register space is used,
all PCC registers, for all processors in the same performance
domain (as defined by _PSD), must be defined to be in the same subspace.
Based on Section 14.1 of ACPI specification, it is possible to have a
maximum of 256 PCC subspace ids. Add support of multiple PCC subspace id
instead of using a single global pcc_data structure.

While at that fix the time_delta check in send_pcc_cmd() so that last_mpar_reset
and mpar_count is initialized properly.

Signed-off-by: George Cherian <george.cherian@xxxxxxxxxx>
---
  drivers/acpi/cppc_acpi.c | 243 +++++++++++++++++++++++++++++------------------
  1 file changed, 153 insertions(+), 90 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index e5b47f0..3ae79ef 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -75,13 +75,16 @@ struct cppc_pcc_data {
  
  	/* Wait queue for CPUs whose requests were batched */
  	wait_queue_head_t pcc_write_wait_q;
+	ktime_t last_cmd_cmpl_time;
+	ktime_t last_mpar_reset;
+	int mpar_count;
+	int refcount;
  };
  
-/* Structure to represent the single PCC channel */
-static struct cppc_pcc_data pcc_data = {
-	.pcc_subspace_idx = -1,
-	.platform_owns_pcc = true,
-};
+/* Array  to represent the PCC channel per subspace id */
+static struct cppc_pcc_data *pcc_data[MAX_PCC_SUBSPACES];
+/* The cpu_pcc_subspace_idx containsper CPU subspace id */
+static DEFINE_PER_CPU(int, cpu_pcc_subspace_idx);
  
  /*
   * The cpc_desc structure contains the ACPI register details
@@ -93,7 +96,8 @@ static struct cppc_pcc_data pcc_data = {
  static DEFINE_PER_CPU(struct cpc_desc *, cpc_desc_ptr);
  
  /* pcc mapped address + header size + offset within PCC subspace */
-#define GET_PCC_VADDR(offs) (pcc_data.pcc_comm_addr + 0x8 + (offs))
+#define GET_PCC_VADDR(offs, pcc_ss_id) (pcc_data[pcc_ss_id]->pcc_comm_addr + \
+						0x8 + (offs))
  
  /* Check if a CPC register is in PCC */
  #define CPC_IN_PCC(cpc) ((cpc)->type == ACPI_TYPE_BUFFER &&		\
@@ -188,13 +192,16 @@ static struct kobj_type cppc_ktype = {
  	.default_attrs = cppc_attrs,
  };
  
-static int check_pcc_chan(bool chk_err_bit)
+static int check_pcc_chan(int pcc_ss_id, bool chk_err_bit)
  {
  	int ret = -EIO, status = 0;
-	struct acpi_pcct_shared_memory __iomem *generic_comm_base = pcc_data.pcc_comm_addr;
-	ktime_t next_deadline = ktime_add(ktime_get(), pcc_data.deadline);
+	struct cppc_pcc_data *pcc_ss_data = pcc_data[pcc_ss_id];
+	struct acpi_pcct_shared_memory __iomem *generic_comm_base =
+		pcc_ss_data->pcc_comm_addr;
+	ktime_t next_deadline = ktime_add(ktime_get(),
+					  pcc_ss_data->deadline);
  
-	if (!pcc_data.platform_owns_pcc)
+	if (!pcc_ss_data->platform_owns_pcc)
  		return 0;
  
  	/* Retry in case the remote processor was too slow to catch up. */
@@ -219,7 +226,7 @@ static int check_pcc_chan(bool chk_err_bit)
  	}
  
  	if (likely(!ret))
-		pcc_data.platform_owns_pcc = false;
+		pcc_ss_data->platform_owns_pcc = false;
  	else
  		pr_err("PCC check channel failed. Status=%x\n", status);
  
@@ -230,13 +237,12 @@ static int check_pcc_chan(bool chk_err_bit)
   * This function transfers the ownership of the PCC to the platform
   * So it must be called while holding write_lock(pcc_lock)
   */
-static int send_pcc_cmd(u16 cmd)
+static int send_pcc_cmd(int pcc_ss_id, u16 cmd)
  {
  	int ret = -EIO, i;
+	struct cppc_pcc_data *pcc_ss_data = pcc_data[pcc_ss_id];
  	struct acpi_pcct_shared_memory *generic_comm_base =
-		(struct acpi_pcct_shared_memory *) pcc_data.pcc_comm_addr;
-	static ktime_t last_cmd_cmpl_time, last_mpar_reset;
-	static int mpar_count;
+		(struct acpi_pcct_shared_memory *)pcc_ss_data->pcc_comm_addr;
  	unsigned int time_delta;
  
  	/*
@@ -249,24 +255,25 @@ static int send_pcc_cmd(u16 cmd)
  		 * before write completion, so first send a WRITE command to
  		 * platform
  		 */
-		if (pcc_data.pending_pcc_write_cmd)
-			send_pcc_cmd(CMD_WRITE);
+		if (pcc_ss_data->pending_pcc_write_cmd)
+			send_pcc_cmd(pcc_ss_id, CMD_WRITE);
  
-		ret = check_pcc_chan(false);
+		ret = check_pcc_chan(pcc_ss_id, false);
  		if (ret)
  			goto end;
  	} else /* CMD_WRITE */
-		pcc_data.pending_pcc_write_cmd = FALSE;
+		pcc_ss_data->pending_pcc_write_cmd = FALSE;
  
  	/*
  	 * 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_data.pcc_mrtt) {
-		time_delta = ktime_us_delta(ktime_get(), last_cmd_cmpl_time);
-		if (pcc_data.pcc_mrtt > time_delta)
-			udelay(pcc_data.pcc_mrtt - time_delta);
+	if (pcc_ss_data->pcc_mrtt) {
+		time_delta = ktime_us_delta(ktime_get(),
+					    pcc_ss_data->last_cmd_cmpl_time);
+		if (pcc_ss_data->pcc_mrtt > time_delta)
+			udelay(pcc_ss_data->pcc_mrtt - time_delta);
  	}
  
  	/*
@@ -280,18 +287,19 @@ static int send_pcc_cmd(u16 cmd)
  	 * not send the request to the platform after hitting the MPAR limit in
  	 * any 60s window
  	 */
-	if (pcc_data.pcc_mpar) {
-		if (mpar_count == 0) {
-			time_delta = ktime_ms_delta(ktime_get(), last_mpar_reset);
-			if (time_delta < 60 * MSEC_PER_SEC) {
+	if (pcc_ss_data->pcc_mpar) {
+		if (pcc_ss_data->mpar_count == 0) {
+			time_delta = ktime_ms_delta(ktime_get(),
+						    pcc_ss_data->last_mpar_reset);
+			if ((time_delta < 60 * MSEC_PER_SEC) && pcc_ss_data->last_mpar_reset) {
  				pr_debug("PCC cmd not sent due to MPAR limit");
  				ret = -EIO;
  				goto end;
  			}
-			last_mpar_reset = ktime_get();
-			mpar_count = pcc_data.pcc_mpar;
+			pcc_ss_data->last_mpar_reset = ktime_get();
+			pcc_ss_data->mpar_count = pcc_ss_data->pcc_mpar;
  		}
-		mpar_count--;
+		pcc_ss_data->mpar_count--;
  	}
  
  	/* Write to the shared comm region. */
@@ -300,10 +308,10 @@ static int send_pcc_cmd(u16 cmd)
  	/* Flip CMD COMPLETE bit */
  	writew_relaxed(0, &generic_comm_base->status);
  
-	pcc_data.platform_owns_pcc = true;
+	pcc_ss_data->platform_owns_pcc = true;
  
  	/* Ring doorbell */
-	ret = mbox_send_message(pcc_data.pcc_channel, &cmd);
+	ret = mbox_send_message(pcc_ss_data->pcc_channel, &cmd);
  	if (ret < 0) {
  		pr_err("Err sending PCC mbox message. cmd:%d, ret:%d\n",
  				cmd, ret);
@@ -311,15 +319,15 @@ static int send_pcc_cmd(u16 cmd)
  	}
  
  	/* wait for completion and check for PCC errro bit */
-	ret = check_pcc_chan(true);
+	ret = check_pcc_chan(pcc_ss_id, true);
  
-	if (pcc_data.pcc_mrtt)
-		last_cmd_cmpl_time = ktime_get();
+	if (pcc_ss_data->pcc_mrtt)
+		pcc_ss_data->last_cmd_cmpl_time = ktime_get();
  
-	if (pcc_data.pcc_channel->mbox->txdone_irq)
-		mbox_chan_txdone(pcc_data.pcc_channel, ret);
+	if (pcc_ss_data->pcc_channel->mbox->txdone_irq)
+		mbox_chan_txdone(pcc_ss_data->pcc_channel, ret);
  	else
-		mbox_client_txdone(pcc_data.pcc_channel, ret);
+		mbox_client_txdone(pcc_ss_data->pcc_channel, ret);
  
  end:
  	if (cmd == CMD_WRITE) {
@@ -329,12 +337,12 @@ static int send_pcc_cmd(u16 cmd)
  				if (!desc)
  					continue;
  
-				if (desc->write_cmd_id == pcc_data.pcc_write_cnt)
+				if (desc->write_cmd_id == pcc_ss_data->pcc_write_cnt)
  					desc->write_cmd_status = ret;
  			}
  		}
-		pcc_data.pcc_write_cnt++;
-		wake_up_all(&pcc_data.pcc_write_wait_q);
+		pcc_ss_data->pcc_write_cnt++;
+		wake_up_all(&pcc_ss_data->pcc_write_wait_q);
  	}
  
  	return ret;
@@ -536,16 +544,16 @@ int acpi_get_psd_map(struct cppc_cpudata **all_cpu_data)
  }
  EXPORT_SYMBOL_GPL(acpi_get_psd_map);
  
-static int register_pcc_channel(int pcc_subspace_idx)
+static int register_pcc_channel(int pcc_ss_idx)
  {
  	struct acpi_pcct_hw_reduced *cppc_ss;
  	u64 usecs_lat;
  
-	if (pcc_subspace_idx >= 0) {
-		pcc_data.pcc_channel = pcc_mbox_request_channel(&cppc_mbox_cl,
-				pcc_subspace_idx);
+	if (pcc_ss_idx >= 0) {
+		pcc_data[pcc_ss_idx]->pcc_channel =
+			pcc_mbox_request_channel(&cppc_mbox_cl,	pcc_ss_idx);
  
-		if (IS_ERR(pcc_data.pcc_channel)) {
+		if (IS_ERR(pcc_data[pcc_ss_idx]->pcc_channel)) {
  			pr_err("Failed to find PCC communication channel\n");
  			return -ENODEV;
  		}
@@ -556,7 +564,7 @@ static int register_pcc_channel(int pcc_subspace_idx)
  		 * PCC channels) and stored pointers to the
  		 * subspace communication region in con_priv.
  		 */
-		cppc_ss = (pcc_data.pcc_channel)->con_priv;
+		cppc_ss = (pcc_data[pcc_ss_idx]->pcc_channel)->con_priv;
  
  		if (!cppc_ss) {
  			pr_err("No PCC subspace found for CPPC\n");
@@ -569,19 +577,20 @@ static int register_pcc_channel(int pcc_subspace_idx)
  		 * So add an arbitrary amount of wait on top of Nominal.
  		 */
  		usecs_lat = NUM_RETRIES * cppc_ss->latency;
-		pcc_data.deadline = ns_to_ktime(usecs_lat * NSEC_PER_USEC);
-		pcc_data.pcc_mrtt = cppc_ss->min_turnaround_time;
-		pcc_data.pcc_mpar = cppc_ss->max_access_rate;
-		pcc_data.pcc_nominal = cppc_ss->latency;
-
-		pcc_data.pcc_comm_addr = acpi_os_ioremap(cppc_ss->base_address, cppc_ss->length);
-		if (!pcc_data.pcc_comm_addr) {
+		pcc_data[pcc_ss_idx]->deadline = ns_to_ktime(usecs_lat * NSEC_PER_USEC);
+		pcc_data[pcc_ss_idx]->pcc_mrtt = cppc_ss->min_turnaround_time;
+		pcc_data[pcc_ss_idx]->pcc_mpar = cppc_ss->max_access_rate;
+		pcc_data[pcc_ss_idx]->pcc_nominal = cppc_ss->latency;
+
+		pcc_data[pcc_ss_idx]->pcc_comm_addr =
+			acpi_os_ioremap(cppc_ss->base_address, cppc_ss->length);
+		if (!pcc_data[pcc_ss_idx]->pcc_comm_addr) {
  			pr_err("Failed to ioremap PCC comm region mem\n");
  			return -ENOMEM;
  		}
  
  		/* Set flag so that we dont come here for each CPU. */
-		pcc_data.pcc_channel_acquired = true;
+		pcc_data[pcc_ss_idx]->pcc_channel_acquired = true;
  	}
  
  	return 0;
@@ -600,6 +609,39 @@ bool __weak cpc_ffh_supported(void)
  	return false;
  }
  
+
+/**
+ * pcc_data_alloc() - Allocate the pcc_data memory for pcc subspace
+ *
+ * Check and allocate the cppc_pcc_data memory.
+ * In some processor configurations it is possible that same subspace
+ * is shared between multiple CPU's. This is seen especially in CPU's
+ * with hardware multi-threading support.
+ *
+ * Return: 0 for success, errno for failure
+ */
+int pcc_data_alloc(int pcc_ss_id)
+{
+	int loop;
+
+	if (pcc_ss_id < 0)
Above should be (pcc_ss_id < 0 || pcc_ss_id >= MAX_PCC_SUBSPACES)
Yes we can have this additional check.
+		return -EINVAL;
+
+	for (loop = 0; pcc_data[loop] != NULL; loop++) {
+		if (pcc_data[loop]->pcc_subspace_idx == pcc_ss_id) {
+			pcc_data[loop]->refcount++;
+			return 0;
+		}
+	}
Why do we need the above for loop? can't it be direct array lookup?
if (pcc_data[pcc_ss_id]) {
     //increment ref_count and return
}
Yes, we could get rid of the loop and increment the reference directly 
if already allocated.


Also, we should remove the pcc_subspace_idx from cppc_pcc_data structure,
it is no longer useful and probably adds to confusion.
Please see below
+
+	pcc_data[pcc_ss_id] = kzalloc(sizeof(struct cppc_pcc_data), GFP_KERNEL);
+	if (!pcc_data[pcc_ss_id])
+		return -ENOMEM;
+	pcc_data[pcc_ss_id]->pcc_subspace_idx = pcc_ss_id;
+	pcc_data[pcc_ss_id]->refcount++;
+
+	return 0;
+}
  /*
   * An example CPC table looks like the following.
   *
@@ -661,6 +703,7 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
  	struct device *cpu_dev;
  	acpi_handle handle = pr->handle;
  	unsigned int num_ent, i, cpc_rev;
+	int pcc_subspace_id = -1;
  	acpi_status status;
  	int ret = -EFAULT;
  
@@ -733,12 +776,9 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
  			 * so extract it only once.
  			 */
  			if (gas_t->space_id == ACPI_ADR_SPACE_PLATFORM_COMM) {
-				if (pcc_data.pcc_subspace_idx < 0)
-					pcc_data.pcc_subspace_idx = gas_t->access_width;
-				else if (pcc_data.pcc_subspace_idx != gas_t->access_width) {
-					pr_debug("Mismatched PCC ids.\n");
We need to retain the above checks to make sure all PCC registers
within a _CPC package is under same subspace. The Spec still requires:
"If the PCC register space is used, all PCC registers, for all processors in
the same performance domain (as defined by _PSD), must be defined
to be in the same subspace."

So that means we need to maintain the pcc_subspace_idx in cppc_pcc_data.
If so, then I can move the check inside pcc_data_alloc().

+				pcc_subspace_id = gas_t->access_width;
+				if (pcc_data_alloc(pcc_subspace_id))
  					goto out_free;
We need to call pcc_data_alloc(to increment the reference) only once per CPU,
otherwise acpi_cppc_processor_exit( ) will never free the memory allocated in
pcc_data.

It is infact called only once per CPU, The refcounting was added in case 
if multiple CPU's share the same domain for eg:
In instances, where CPU have hardware multi-threading support.
or in cases where all CPU's are controlled using single subspace (as 
earlier).

Do you see any issue with acpi_cppc_processor_exit() in the earlier 
cases, where refcount remains > 0 and the memory not getting freed-up?


--
Thanks,
Prashanth

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