[PATCH v7 0/2] PCC: Platform Communication Channel

[PATCH v7 0/2] PCC: Platform Communication Channel

[Ashwin Chaugule]

Changes since V6:
- Cosmetic changes based on Lv's suggestions

Changes since V5:
- Optimize loop that matches channel request.
- Use platform_create_bundle.
- Replace ioread/writes.
- Remove redundant code and headers.
- Restructure common mailbox macros.
- Reformat PCC cmd parsing.

Changes since V4:
- Folded PCC Mailbox helpers into pcc.c

Changes since V3:
- Added PCC helper functions to work around "struct device" limitations.
- PCC driver changes to work with PCC specific Mailbox helpers.

Changes since V2:
- Rebased on top of git://git.linaro.org/landing-teams/working/fujitsu/integration.git
        branch mailbox-for-3.17
- Added PCC API to mailbox framework as per Arnd's suggestion to allow usage without ACPI.

Changes since V1:
- Integration with Mailbox framework - https://lkml.org/lkml/2014/5/15/49

This patchset adds support for the PCC (Platform Communication Channel)
interface as described in the current ACPI 5.0 spec. See Section 14 of the
ACPI spec - http://acpi.info/DOWNLOADS/ACPI_5_Errata%20A.pdf for more details
on how PCC works.

In brief PCC is a generic means for PCC clients, to talk to the firmware. The
PCC register space is typically memory mapped IO and uses a doorbell mechanism
to communicate synchronously from the OS to the firmware. The PCC driver is
completely agnostic to the protocol implemented by the PCC clients. It only
implements the enumeration of PCC channels and the low level transport mechanism
and leaves the rest to the PCC clients.

The PCC is meant to be useable in the future by clients such as CPPC
(Collaborative Processor Performance Control), RAS (Reliability,
Availability and Serviceability) and MPST (Memory Power State Tables) and possibly others.

Ashwin Chaugule (2):
  Mailbox: Add support for Platform Communication Channel
  PCC test

 drivers/mailbox/Kconfig    |  12 ++
 drivers/mailbox/Makefile   |   2 +
 drivers/mailbox/mailbox.c  |   4 +-
 drivers/mailbox/mailbox.h  |  16 +++
 drivers/mailbox/pcc-test.c | 203 ++++++++++++++++++++++++++++++++
 drivers/mailbox/pcc.c      | 282 +++++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 516 insertions(+), 3 deletions(-)
 create mode 100644 drivers/mailbox/mailbox.h
 create mode 100644 drivers/mailbox/pcc-test.c
 create mode 100644 drivers/mailbox/pcc.c

-- 
1.9.1

[PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Ashwin Chaugule]

ACPI 5.0+ spec defines a generic mode of communication
between the OS and a platform such as the BMC. This medium
(PCC) is typically used by CPPC (ACPI CPU Performance management),
RAS (ACPI reliability protocol) and MPST (ACPI Memory power
states).

This patch adds PCC support as a Mailbox Controller.

Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
---
 drivers/mailbox/Kconfig   |  12 ++
 drivers/mailbox/Makefile  |   2 +
 drivers/mailbox/mailbox.c |   4 +-
 drivers/mailbox/mailbox.h |  16 +++
 drivers/mailbox/pcc.c     | 282 ++++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 313 insertions(+), 3 deletions(-)
 create mode 100644 drivers/mailbox/mailbox.h
 create mode 100644 drivers/mailbox/pcc.c

diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index c8b5c13..e08cc83 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -50,4 +50,16 @@ config OMAP_MBOX_KFIFO_SIZE
 	  Specify the default size of mailbox's kfifo buffers (bytes).
 	  This can also be changed at runtime (via the mbox_kfifo_size
 	  module parameter).
+
+config PCC
+	bool "Platform Communication Channel Driver"
+	depends on ACPI
+	help
+		ACPI 5.0+ spec defines a generic mode of communication
+		between the OS and a platform such as the BMC. This medium
+		(PCC) is typically used by CPPC (ACPI CPU Performance management),
+		RAS (ACPI reliability protocol) and MPST (ACPI Memory power
+		states). Select this driver if your platform implements the
+		PCC clients mentioned above.
+
 endif
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index 2fa343a..0b09d6f 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -9,3 +9,5 @@ obj-$(CONFIG_OMAP1_MBOX)	+= mailbox_omap1.o
 mailbox_omap1-objs		:= mailbox-omap1.o
 obj-$(CONFIG_OMAP2PLUS_MBOX)	+= mailbox_omap2.o
 mailbox_omap2-objs		:= mailbox-omap2.o
+
+obj-$(CONFIG_PCC)			+= pcc.o
diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 63ecc17..9d9366a 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -21,9 +21,7 @@
 #include <linux/mailbox_client.h>
 #include <linux/mailbox_controller.h>
 
-#define TXDONE_BY_IRQ	BIT(0) /* controller has remote RTR irq */
-#define TXDONE_BY_POLL	BIT(1) /* controller can read status of last TX */
-#define TXDONE_BY_ACK	BIT(2) /* S/W ACK recevied by Client ticks the TX */
+#include "mailbox.h"
 
 static LIST_HEAD(mbox_cons);
 static DEFINE_MUTEX(con_mutex);
diff --git a/drivers/mailbox/mailbox.h b/drivers/mailbox/mailbox.h
new file mode 100644
index 0000000..5a15a25
--- /dev/null
+++ b/drivers/mailbox/mailbox.h
@@ -0,0 +1,16 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#ifndef __MAILBOX_H
+#define __MAILBOX_H
+
+#define TXDONE_BY_IRQ	BIT(0) /* controller has remote RTR irq */
+#define TXDONE_BY_POLL	BIT(1) /* controller can read status of last TX */
+#define TXDONE_BY_ACK	BIT(2) /* S/W ACK recevied by Client ticks the TX */
+
+#endif /* __MAILBOX_H */
+
+
diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
new file mode 100644
index 0000000..bb8e8b1
--- /dev/null
+++ b/drivers/mailbox/pcc.c
@@ -0,0 +1,282 @@
+/*
+ *	Copyright (C) 2014 Linaro Ltd.
+ *	Author:	Ashwin Chaugule <ashwin.chaugule@linaro.org>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ */
+
+#include <linux/acpi.h>
+#include <linux/cpufreq.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/ioctl.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/vmalloc.h>
+#include <linux/platform_device.h>
+#include <linux/mailbox_controller.h>
+#include <linux/mailbox_client.h>
+
+#include "mailbox.h"
+
+#define MAX_PCC_SUBSPACES	256
+#define PCCS_SS_SIG_MAGIC	0x50434300
+#define PCC_CMD_COMPLETE	0x1
+
+static struct mbox_chan pcc_mbox_chan[MAX_PCC_SUBSPACES];
+static struct mbox_controller pcc_mbox_ctrl = {};
+
+struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
+		int index)
+{
+	struct device *dev = pcc_mbox_ctrl.dev;
+	struct mbox_chan *chan;
+	unsigned long flags;
+
+	/*
+	 * Each PCC Subspace is a Mailbox Channel.
+	 * The PCC Clients get their PCC Subspace ID
+	 * from their own tables and pass it here.
+	 * This returns a pointer to the PCC subspace
+	 * for the Client to operate on.
+	 */
+	chan = &pcc_mbox_chan[index];
+
+	if (!chan || chan->cl) {
+		dev_err(dev, "%s: PCC mailbox not free\n", __func__);
+		return ERR_PTR(-EBUSY);
+	}
+
+	spin_lock_irqsave(&chan->lock, flags);
+	chan->msg_free = 0;
+	chan->msg_count = 0;
+	chan->active_req = NULL;
+	chan->cl = cl;
+	init_completion(&chan->tx_complete);
+
+	if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
+		chan->txdone_method |= TXDONE_BY_ACK;
+
+	spin_unlock_irqrestore(&chan->lock, flags);
+
+	return chan;
+}
+EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);
+
+void pcc_mbox_free_channel(struct mbox_chan *chan)
+{
+	unsigned long flags;
+
+	if (!chan || !chan->cl)
+		return;
+
+	spin_lock_irqsave(&chan->lock, flags);
+	chan->cl = NULL;
+	chan->active_req = NULL;
+	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
+		chan->txdone_method = TXDONE_BY_POLL;
+
+	spin_unlock_irqrestore(&chan->lock, flags);
+}
+EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
+
+static bool pcc_tx_done(struct mbox_chan *chan)
+{
+	struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
+	struct acpi_pcct_shared_memory *generic_comm_base =
+		(struct acpi_pcct_shared_memory *) pcct_ss->base_address;
+	u16 cmd_delay = pcct_ss->min_turnaround_time;
+
+	/* Wait for Platform to consume. */
+	while (!(readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE))
+		udelay(cmd_delay);
+
+	return true;
+}
+
+static int get_subspace_id(struct mbox_chan *chan)
+{
+	int id = chan - pcc_mbox_chan;
+
+	if (id < 0 || id > pcc_mbox_ctrl.num_chans)
+		return -ENOENT;
+
+	return id;
+}
+
+/* Channel lock is already held by mbox controller code. */
+static int pcc_send_data(struct mbox_chan *chan, void *data)
+{
+	struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
+	struct acpi_pcct_shared_memory *generic_comm_base =
+		(struct acpi_pcct_shared_memory *) pcct_ss->base_address;
+	struct acpi_generic_address doorbell;
+	u64 doorbell_preserve;
+	u64 doorbell_val;
+	u64 doorbell_write;
+	u16 cmd = *(u16 *) data;
+	u16 ss_idx = -1;
+	int ret = 0;
+
+	ss_idx = get_subspace_id(chan);
+
+	if (ss_idx < 0) {
+		pr_err("Invalid Subspace ID from PCC client\n");
+		ret = -EINVAL;
+		goto out_err;
+	}
+
+	doorbell = pcct_ss->doorbell_register;
+	doorbell_preserve = pcct_ss->preserve_mask;
+	doorbell_write = pcct_ss->write_mask;
+
+	/* Write to the shared comm region. */
+	writew(cmd, &generic_comm_base->command);
+
+	/* Write Subspace MAGIC value so platform can identify destination. */
+	writel((PCCS_SS_SIG_MAGIC | ss_idx), &generic_comm_base->signature);
+
+	/* Flip CMD COMPLETE bit */
+	writew(0, &generic_comm_base->status);
+
+	/* Sync notification from OSPM to Platform. */
+	acpi_read(&doorbell_val, &doorbell);
+	acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
+			&doorbell);
+
+out_err:
+	return ret;
+}
+
+static struct mbox_chan_ops pcc_chan_ops = {
+	.send_data = pcc_send_data,
+	.last_tx_done = pcc_tx_done,
+};
+
+static int parse_pcc_subspace(struct acpi_subtable_header *header,
+		const unsigned long end)
+{
+	struct acpi_pcct_subspace *pcct_ss;
+
+	if (pcc_mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) {
+		pcct_ss = (struct acpi_pcct_subspace *) header;
+
+		if (pcct_ss->header.type != ACPI_PCCT_TYPE_GENERIC_SUBSPACE) {
+			pr_err("Incorrect PCC Subspace type detected\n");
+			return -EINVAL;
+		}
+
+		/* New mbox channel entry for each PCC subspace detected. */
+		pcc_mbox_chan[pcc_mbox_ctrl.num_chans].con_priv = pcct_ss;
+		pcc_mbox_ctrl.num_chans++;
+
+	} else {
+		pr_err("No more space for PCC subspaces.\n");
+		return -ENOSPC;
+	}
+
+	return 0;
+}
+
+static int __init acpi_pcc_probe(void)
+{
+	acpi_status status = AE_OK;
+	acpi_size pcct_tbl_header_size;
+	struct acpi_table_pcct *pcct_tbl;
+
+	/* Search for PCCT */
+	status = acpi_get_table_with_size(ACPI_SIG_PCCT, 0,
+			(struct acpi_table_header **)&pcct_tbl,
+			&pcct_tbl_header_size);
+
+	if (ACPI_SUCCESS(status) && !pcct_tbl) {
+		pr_warn("PCCT header not found.\n");
+		status = AE_NOT_FOUND;
+		goto out_err;
+	}
+
+	status = acpi_table_parse_entries(ACPI_SIG_PCCT,
+			sizeof(struct acpi_table_pcct),
+			ACPI_PCCT_TYPE_GENERIC_SUBSPACE,
+			parse_pcc_subspace, MAX_PCC_SUBSPACES);
+
+	if (ACPI_SUCCESS(status)) {
+		pr_err("Error parsing PCC subspaces from PCCT\n");
+		status = AE_ERROR;
+		goto out_err;
+	}
+
+	pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);
+
+	pcc_mbox_ctrl.chans = pcc_mbox_chan;
+	pcc_mbox_ctrl.ops = &pcc_chan_ops;
+	pcc_mbox_ctrl.txdone_poll = true;
+	pcc_mbox_ctrl.txpoll_period = 1;
+
+out_err:
+	return ACPI_SUCCESS(status) ? -EINVAL : 0;
+}
+
+static int pcc_mbox_probe(struct platform_device *pdev)
+{
+	int ret = 0;
+
+	pcc_mbox_ctrl.dev = &pdev->dev;
+
+	pr_info("Registering PCC driver as Mailbox controller\n");
+	ret = mbox_controller_register(&pcc_mbox_ctrl);
+
+	if (ret) {
+		pr_err("Err registering PCC as Mailbox controller: %d\n", ret);
+		ret = -ENODEV;
+	}
+
+	return ret;
+}
+
+struct platform_driver pcc_mbox_driver = {
+	.probe = pcc_mbox_probe,
+	.driver = {
+		.name = "PCCT",
+		.owner = THIS_MODULE,
+	},
+};
+
+static int __init pcc_init(void)
+{
+	int ret;
+	struct platform_device *pcc_pdev;
+
+	if (acpi_disabled)
+		return -ENODEV;
+
+	/* Check if PCC support is available. */
+	ret = acpi_pcc_probe();
+
+	if (ret) {
+		pr_debug("ACPI PCC probe failed.\n");
+		return -ENODEV;
+	}
+
+	pcc_pdev = platform_create_bundle(&pcc_mbox_driver,
+			pcc_mbox_probe, NULL, 0, NULL, 0);
+
+	if (!pcc_pdev) {
+		pr_err("Err creating PCC platform bundle\n");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+device_initcall(pcc_init);
-- 
1.9.1

[PATCH v7 2/2] PCC test

[Ashwin Chaugule]

Not for upstreaming. This is only to show how the PCC driver was
tested.

echo 2 > /proc/pcc_test [ to get the PCC base address from the PCCT ]

echo 1 > /proc/pcc_test [ to trigger a PCC write ]

echo 0 > /proc/pcc_test [ to trigger a PCC read ]

dmesg shows the output.

Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
---
 drivers/mailbox/Makefile   |   2 +-
 drivers/mailbox/pcc-test.c | 203 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 204 insertions(+), 1 deletion(-)
 create mode 100644 drivers/mailbox/pcc-test.c

diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index 0b09d6f..028b8b1 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -10,4 +10,4 @@ mailbox_omap1-objs		:= mailbox-omap1.o
 obj-$(CONFIG_OMAP2PLUS_MBOX)	+= mailbox_omap2.o
 mailbox_omap2-objs		:= mailbox-omap2.o
 
-obj-$(CONFIG_PCC)			+= pcc.o
+obj-$(CONFIG_PCC)			+= pcc.o pcc-test.o
diff --git a/drivers/mailbox/pcc-test.c b/drivers/mailbox/pcc-test.c
new file mode 100644
index 0000000..9412a7a
--- /dev/null
+++ b/drivers/mailbox/pcc-test.c
@@ -0,0 +1,203 @@
+/*
+ *	Copyright (C) 2014 Linaro Ltd.
+ *	Author:	Ashwin Chaugule <ashwin.chaugule@linaro.org>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ */
+
+#include <linux/acpi.h>
+#include <linux/io.h>
+#include <linux/uaccess.h>
+#include <linux/init.h>
+#include <linux/cpufreq.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/mailbox_client.h>
+#include <linux/mailbox_controller.h>
+#include <linux/platform_device.h>
+#include <asm/uaccess.h>
+
+#include <acpi/actbl.h>
+
+static void __iomem *comm_base_addr; 	/* For use after ioremap */
+
+extern struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *, unsigned int);
+extern int mbox_send_message(struct mbox_chan *chan, void *mssg);
+
+
+/* XXX: The PCC Subspace id is hard coded here only for test purposes.
+ * In reality it should be parsed from the PCC package as described
+ * in the PCC client table. e.g. CPC for CPPC 
+ */
+#define PCC_SUBSPACE_IDX 0
+#define CMD_COMPLETE    1
+
+struct mbox_chan *pcc_test_chan;
+enum ppc_cmds {
+	CMD_READ,
+	CMD_WRITE,
+	RESERVED,
+};
+
+static u64 reg1, reg2;
+
+static void run_pcc_test_read(void)
+{
+	u64 reg1_addr = (u64)comm_base_addr + 0x100;
+	u64 reg2_addr = (u64)comm_base_addr + 0x110;
+	u16 cmd = CMD_READ;
+	int ret;
+
+	/* READ part of the test */
+	pr_info("Sending PCC read req from Channel base addr: %llx\n", (u64)comm_base_addr);
+	ret = mbox_send_message(pcc_test_chan, &cmd);
+	if (ret >= 0) {
+		pr_info("Read updated values from Platform.\n");
+		reg1 = readq((void*)reg1_addr);
+		reg2 = readq((void*)reg2_addr);
+		pr_info("updated value of reg1:%llx\n", reg1);
+		pr_info("updated value of reg2:%llx\n", reg2);
+	} else
+		pr_err("Failed to read PCC parameters: ret=%d\n", ret);
+}
+
+static void run_pcc_test_write(void)
+{
+	u64 reg1_addr = (u64)comm_base_addr + 0x100;
+	u64 reg2_addr = (u64)comm_base_addr + 0x110;
+	u16 cmd = CMD_WRITE;
+	int ret;
+
+	/* WRITE part of the test */
+	reg1++;
+	reg2++;
+
+	writeq(reg1, (void *)reg1_addr);
+	writeq(reg2, (void *)reg2_addr);
+
+	pr_info("Sending PCC write req from Channel base addr: %llx\n", (u64)comm_base_addr);
+	ret = mbox_send_message(pcc_test_chan, &cmd);
+
+	if (ret >= 0)
+		pr_info("OSPM successfully sent PCC write cmd to platform\n");
+	else
+		pr_err("Failed to write PCC parameters. ret= %d\n", ret);
+}
+
+static void pcc_chan_tx_done(struct mbox_client *cl, void *mssg, int ret)
+{
+	if (!ret)
+		pr_info("PCC channel TX successfully completed. CMD sent = %x\n", *(u16*)mssg);
+	else
+		pr_warn("PCC channel TX did not complete: CMD sent = %x\n", *(u16*)mssg);
+}
+
+struct mbox_client pcc_mbox_cl = {
+	.tx_done	=	pcc_chan_tx_done,
+};
+
+void get_pcc_comm(void)
+{
+	u64 base_addr;
+	u32 len;
+	struct acpi_pcct_subspace *pcc_ss;
+
+	pcc_test_chan = pcc_mbox_request_channel(&pcc_mbox_cl, PCC_SUBSPACE_IDX);
+
+	if (!pcc_test_chan) {
+		pr_err("PCC Channel not found!\n");
+		return;
+	}
+
+	pcc_ss = pcc_test_chan->con_priv;
+
+	base_addr = pcc_ss->base_address;
+	len = pcc_ss->length;
+
+	pr_info("ioremapping: %llx, len: %x\n", base_addr, len);
+
+//	comm_base_addr = ioremap_nocache(base_addr, len);
+	/* HACK to test PCC commands */
+	comm_base_addr = kzalloc(PAGE_SIZE, GFP_KERNEL);
+
+	if (!comm_base_addr) {
+		pr_err("Could not ioremap channel\n");
+		return;
+	}
+
+	pcc_ss->base_address = (u64)comm_base_addr;
+
+	pr_info("Comm_base_addr: %llx\n", (u64)comm_base_addr);
+}
+
+static ssize_t pcc_test_write(struct file *file, const char __user *buf,
+		size_t count, loff_t *offs)
+{
+	char ctl[2];
+
+	if (count != 2 || *offs)
+		return -EINVAL;
+
+	if (copy_from_user(ctl, buf, count))
+		return -EFAULT;
+
+	switch (ctl[0]) {
+		case '0':
+			/* PCC read */
+			run_pcc_test_read();
+			break;
+		case '1':
+			/* PCC write */
+			run_pcc_test_write();
+			break;
+		case '2':
+			/* Get PCC channel */
+			get_pcc_comm();
+			break;
+		default:
+			pr_err("Unknown val\n");
+			break;
+	}
+
+	return count;
+}
+
+static int pcc_test_open(struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+static int pcc_test_release(struct inode *inode, struct file *filp)
+{
+	return 0;
+}
+
+static const struct file_operations pcc_test_fops = {
+	.open		= pcc_test_open,
+//	.read		= seq_read,
+	.write		= pcc_test_write,
+	.release	= pcc_test_release,
+};
+
+static int __init pcc_test(void)
+{
+	struct proc_dir_entry *pe;
+
+	pe = proc_create("pcc_test", 0644, NULL, &pcc_test_fops);
+
+	if (!pe)
+		return -ENOMEM;
+
+	return 0;
+}
+
+late_initcall(pcc_test);
-- 
1.9.1

Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Ashwin Chaugule]

Hello,

On 10 September 2014 13:20, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote:
> ACPI 5.0+ spec defines a generic mode of communication
> between the OS and a platform such as the BMC. This medium
> (PCC) is typically used by CPPC (ACPI CPU Performance management),
> RAS (ACPI reliability protocol) and MPST (ACPI Memory power
> states).
>
> This patch adds PCC support as a Mailbox Controller.
>
> Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
> ---
>  drivers/mailbox/Kconfig   |  12 ++
>  drivers/mailbox/Makefile  |   2 +
>  drivers/mailbox/mailbox.c |   4 +-
>  drivers/mailbox/mailbox.h |  16 +++
>  drivers/mailbox/pcc.c     | 282 ++++++++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 313 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/mailbox/mailbox.h
>  create mode 100644 drivers/mailbox/pcc.c

How does this version look? If there are no more changes, please let
me know which tree this can be picked by and I can send a pull request
if that is preferred for this single patch.

Cheers,
Ashwin

>
> diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
> index c8b5c13..e08cc83 100644
> --- a/drivers/mailbox/Kconfig
> +++ b/drivers/mailbox/Kconfig
> @@ -50,4 +50,16 @@ config OMAP_MBOX_KFIFO_SIZE
>           Specify the default size of mailbox's kfifo buffers (bytes).
>           This can also be changed at runtime (via the mbox_kfifo_size
>           module parameter).
> +
> +config PCC
> +       bool "Platform Communication Channel Driver"
> +       depends on ACPI
> +       help
> +               ACPI 5.0+ spec defines a generic mode of communication
> +               between the OS and a platform such as the BMC. This medium
> +               (PCC) is typically used by CPPC (ACPI CPU Performance management),
> +               RAS (ACPI reliability protocol) and MPST (ACPI Memory power
> +               states). Select this driver if your platform implements the
> +               PCC clients mentioned above.
> +
>  endif
> diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
> index 2fa343a..0b09d6f 100644
> --- a/drivers/mailbox/Makefile
> +++ b/drivers/mailbox/Makefile
> @@ -9,3 +9,5 @@ obj-$(CONFIG_OMAP1_MBOX)        += mailbox_omap1.o
>  mailbox_omap1-objs             := mailbox-omap1.o
>  obj-$(CONFIG_OMAP2PLUS_MBOX)   += mailbox_omap2.o
>  mailbox_omap2-objs             := mailbox-omap2.o
> +
> +obj-$(CONFIG_PCC)                      += pcc.o
> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
> index 63ecc17..9d9366a 100644
> --- a/drivers/mailbox/mailbox.c
> +++ b/drivers/mailbox/mailbox.c
> @@ -21,9 +21,7 @@
>  #include <linux/mailbox_client.h>
>  #include <linux/mailbox_controller.h>
>
> -#define TXDONE_BY_IRQ  BIT(0) /* controller has remote RTR irq */
> -#define TXDONE_BY_POLL BIT(1) /* controller can read status of last TX */
> -#define TXDONE_BY_ACK  BIT(2) /* S/W ACK recevied by Client ticks the TX */
> +#include "mailbox.h"
>
>  static LIST_HEAD(mbox_cons);
>  static DEFINE_MUTEX(con_mutex);
> diff --git a/drivers/mailbox/mailbox.h b/drivers/mailbox/mailbox.h
> new file mode 100644
> index 0000000..5a15a25
> --- /dev/null
> +++ b/drivers/mailbox/mailbox.h
> @@ -0,0 +1,16 @@
> +/*
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#ifndef __MAILBOX_H
> +#define __MAILBOX_H
> +
> +#define TXDONE_BY_IRQ  BIT(0) /* controller has remote RTR irq */
> +#define TXDONE_BY_POLL BIT(1) /* controller can read status of last TX */
> +#define TXDONE_BY_ACK  BIT(2) /* S/W ACK recevied by Client ticks the TX */
> +
> +#endif /* __MAILBOX_H */
> +
> +
> diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
> new file mode 100644
> index 0000000..bb8e8b1
> --- /dev/null
> +++ b/drivers/mailbox/pcc.c
> @@ -0,0 +1,282 @@
> +/*
> + *     Copyright (C) 2014 Linaro Ltd.
> + *     Author: Ashwin Chaugule <ashwin.chaugule@linaro.org>
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; either version 2 of the License, or
> + *  (at your option) any later version.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/cpufreq.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/init.h>
> +#include <linux/ioctl.h>
> +#include <linux/module.h>
> +#include <linux/uaccess.h>
> +#include <linux/vmalloc.h>
> +#include <linux/platform_device.h>
> +#include <linux/mailbox_controller.h>
> +#include <linux/mailbox_client.h>
> +
> +#include "mailbox.h"
> +
> +#define MAX_PCC_SUBSPACES      256
> +#define PCCS_SS_SIG_MAGIC      0x50434300
> +#define PCC_CMD_COMPLETE       0x1
> +
> +static struct mbox_chan pcc_mbox_chan[MAX_PCC_SUBSPACES];
> +static struct mbox_controller pcc_mbox_ctrl = {};
> +
> +struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
> +               int index)
> +{
> +       struct device *dev = pcc_mbox_ctrl.dev;
> +       struct mbox_chan *chan;
> +       unsigned long flags;
> +
> +       /*
> +        * Each PCC Subspace is a Mailbox Channel.
> +        * The PCC Clients get their PCC Subspace ID
> +        * from their own tables and pass it here.
> +        * This returns a pointer to the PCC subspace
> +        * for the Client to operate on.
> +        */
> +       chan = &pcc_mbox_chan[index];
> +
> +       if (!chan || chan->cl) {
> +               dev_err(dev, "%s: PCC mailbox not free\n", __func__);
> +               return ERR_PTR(-EBUSY);
> +       }
> +
> +       spin_lock_irqsave(&chan->lock, flags);
> +       chan->msg_free = 0;
> +       chan->msg_count = 0;
> +       chan->active_req = NULL;
> +       chan->cl = cl;
> +       init_completion(&chan->tx_complete);
> +
> +       if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
> +               chan->txdone_method |= TXDONE_BY_ACK;
> +
> +       spin_unlock_irqrestore(&chan->lock, flags);
> +
> +       return chan;
> +}
> +EXPORT_SYMBOL_GPL(pcc_mbox_request_channel);
> +
> +void pcc_mbox_free_channel(struct mbox_chan *chan)
> +{
> +       unsigned long flags;
> +
> +       if (!chan || !chan->cl)
> +               return;
> +
> +       spin_lock_irqsave(&chan->lock, flags);
> +       chan->cl = NULL;
> +       chan->active_req = NULL;
> +       if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
> +               chan->txdone_method = TXDONE_BY_POLL;
> +
> +       spin_unlock_irqrestore(&chan->lock, flags);
> +}
> +EXPORT_SYMBOL_GPL(pcc_mbox_free_channel);
> +
> +static bool pcc_tx_done(struct mbox_chan *chan)
> +{
> +       struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
> +       struct acpi_pcct_shared_memory *generic_comm_base =
> +               (struct acpi_pcct_shared_memory *) pcct_ss->base_address;
> +       u16 cmd_delay = pcct_ss->min_turnaround_time;
> +
> +       /* Wait for Platform to consume. */
> +       while (!(readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE))
> +               udelay(cmd_delay);
> +
> +       return true;
> +}
> +
> +static int get_subspace_id(struct mbox_chan *chan)
> +{
> +       int id = chan - pcc_mbox_chan;
> +
> +       if (id < 0 || id > pcc_mbox_ctrl.num_chans)
> +               return -ENOENT;
> +
> +       return id;
> +}
> +
> +/* Channel lock is already held by mbox controller code. */
> +static int pcc_send_data(struct mbox_chan *chan, void *data)
> +{
> +       struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
> +       struct acpi_pcct_shared_memory *generic_comm_base =
> +               (struct acpi_pcct_shared_memory *) pcct_ss->base_address;
> +       struct acpi_generic_address doorbell;
> +       u64 doorbell_preserve;
> +       u64 doorbell_val;
> +       u64 doorbell_write;
> +       u16 cmd = *(u16 *) data;
> +       u16 ss_idx = -1;
> +       int ret = 0;
> +
> +       ss_idx = get_subspace_id(chan);
> +
> +       if (ss_idx < 0) {
> +               pr_err("Invalid Subspace ID from PCC client\n");
> +               ret = -EINVAL;
> +               goto out_err;
> +       }
> +
> +       doorbell = pcct_ss->doorbell_register;
> +       doorbell_preserve = pcct_ss->preserve_mask;
> +       doorbell_write = pcct_ss->write_mask;
> +
> +       /* Write to the shared comm region. */
> +       writew(cmd, &generic_comm_base->command);
> +
> +       /* Write Subspace MAGIC value so platform can identify destination. */
> +       writel((PCCS_SS_SIG_MAGIC | ss_idx), &generic_comm_base->signature);
> +
> +       /* Flip CMD COMPLETE bit */
> +       writew(0, &generic_comm_base->status);
> +
> +       /* Sync notification from OSPM to Platform. */
> +       acpi_read(&doorbell_val, &doorbell);
> +       acpi_write((doorbell_val & doorbell_preserve) | doorbell_write,
> +                       &doorbell);
> +
> +out_err:
> +       return ret;
> +}
> +
> +static struct mbox_chan_ops pcc_chan_ops = {
> +       .send_data = pcc_send_data,
> +       .last_tx_done = pcc_tx_done,
> +};
> +
> +static int parse_pcc_subspace(struct acpi_subtable_header *header,
> +               const unsigned long end)
> +{
> +       struct acpi_pcct_subspace *pcct_ss;
> +
> +       if (pcc_mbox_ctrl.num_chans <= MAX_PCC_SUBSPACES) {
> +               pcct_ss = (struct acpi_pcct_subspace *) header;
> +
> +               if (pcct_ss->header.type != ACPI_PCCT_TYPE_GENERIC_SUBSPACE) {
> +                       pr_err("Incorrect PCC Subspace type detected\n");
> +                       return -EINVAL;
> +               }
> +
> +               /* New mbox channel entry for each PCC subspace detected. */
> +               pcc_mbox_chan[pcc_mbox_ctrl.num_chans].con_priv = pcct_ss;
> +               pcc_mbox_ctrl.num_chans++;
> +
> +       } else {
> +               pr_err("No more space for PCC subspaces.\n");
> +               return -ENOSPC;
> +       }
> +
> +       return 0;
> +}
> +
> +static int __init acpi_pcc_probe(void)
> +{
> +       acpi_status status = AE_OK;
> +       acpi_size pcct_tbl_header_size;
> +       struct acpi_table_pcct *pcct_tbl;
> +
> +       /* Search for PCCT */
> +       status = acpi_get_table_with_size(ACPI_SIG_PCCT, 0,
> +                       (struct acpi_table_header **)&pcct_tbl,
> +                       &pcct_tbl_header_size);
> +
> +       if (ACPI_SUCCESS(status) && !pcct_tbl) {
> +               pr_warn("PCCT header not found.\n");
> +               status = AE_NOT_FOUND;
> +               goto out_err;
> +       }
> +
> +       status = acpi_table_parse_entries(ACPI_SIG_PCCT,
> +                       sizeof(struct acpi_table_pcct),
> +                       ACPI_PCCT_TYPE_GENERIC_SUBSPACE,
> +                       parse_pcc_subspace, MAX_PCC_SUBSPACES);
> +
> +       if (ACPI_SUCCESS(status)) {
> +               pr_err("Error parsing PCC subspaces from PCCT\n");
> +               status = AE_ERROR;
> +               goto out_err;
> +       }
> +
> +       pr_info("Detected %d PCC Subspaces\n", pcc_mbox_ctrl.num_chans);
> +
> +       pcc_mbox_ctrl.chans = pcc_mbox_chan;
> +       pcc_mbox_ctrl.ops = &pcc_chan_ops;
> +       pcc_mbox_ctrl.txdone_poll = true;
> +       pcc_mbox_ctrl.txpoll_period = 1;
> +
> +out_err:
> +       return ACPI_SUCCESS(status) ? -EINVAL : 0;
> +}
> +
> +static int pcc_mbox_probe(struct platform_device *pdev)
> +{
> +       int ret = 0;
> +
> +       pcc_mbox_ctrl.dev = &pdev->dev;
> +
> +       pr_info("Registering PCC driver as Mailbox controller\n");
> +       ret = mbox_controller_register(&pcc_mbox_ctrl);
> +
> +       if (ret) {
> +               pr_err("Err registering PCC as Mailbox controller: %d\n", ret);
> +               ret = -ENODEV;
> +       }
> +
> +       return ret;
> +}
> +
> +struct platform_driver pcc_mbox_driver = {
> +       .probe = pcc_mbox_probe,
> +       .driver = {
> +               .name = "PCCT",
> +               .owner = THIS_MODULE,
> +       },
> +};
> +
> +static int __init pcc_init(void)
> +{
> +       int ret;
> +       struct platform_device *pcc_pdev;
> +
> +       if (acpi_disabled)
> +               return -ENODEV;
> +
> +       /* Check if PCC support is available. */
> +       ret = acpi_pcc_probe();
> +
> +       if (ret) {
> +               pr_debug("ACPI PCC probe failed.\n");
> +               return -ENODEV;
> +       }
> +
> +       pcc_pdev = platform_create_bundle(&pcc_mbox_driver,
> +                       pcc_mbox_probe, NULL, 0, NULL, 0);
> +
> +       if (!pcc_pdev) {
> +               pr_err("Err creating PCC platform bundle\n");
> +               return -ENODEV;
> +       }
> +
> +       return 0;
> +}
> +
> +device_initcall(pcc_init);
> --
> 1.9.1
>

Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 661 bytes --]

On Fri, Sep 12, 2014 at 09:08:08AM -0400, Ashwin Chaugule wrote:
> On 10 September 2014 13:20, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote:

> How does this version look? If there are no more changes, please let
> me know which tree this can be picked by and I can send a pull request
> if that is preferred for this single patch.

Please allow a reasonable time for review - you're nagging after two
days, this is unreasonable for something that isn't super urgent.  Two
weeks would be more reasonable.  As things stand you're adding to the
mail volume and some people will actively delay looking at things in
order to avoid encouraging such behaviour.

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Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Ashwin Chaugule]

Hi Mark,

On 13 September 2014 11:57, Mark Brown <broonie@kernel.org> wrote:
> On Fri, Sep 12, 2014 at 09:08:08AM -0400, Ashwin Chaugule wrote:
>> On 10 September 2014 13:20, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote:
>
>> How does this version look? If there are no more changes, please let
>> me know which tree this can be picked by and I can send a pull request
>> if that is preferred for this single patch.
>
> Please allow a reasonable time for review - you're nagging after two
> days, this is unreasonable for something that isn't super urgent.  Two
> weeks would be more reasonable.  As things stand you're adding to the
> mail volume and some people will actively delay looking at things in
> order to avoid encouraging such behaviour.

I apologize if it seems that way. I very much appreciate the help I've
received so far. I'd sent V6 9 days ago and only Lv had feedback
around cosmetic changes. Given the simplicity of this patch and all
the previous suggestions, it seemed like we're nearly done with the
reviews. I understand your point though and look forward to seeing
this patch progress.

Thanks,
Ashwin

RE: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Zheng, Lv]

Hi, Ashwin

> From: Ashwin Chaugule [mailto:ashwin.chaugule@linaro.org]
> Sent: Sunday, September 14, 2014 6:05 AM
> 
> Hi Mark,
> 
> On 13 September 2014 11:57, Mark Brown <broonie@kernel.org> wrote:
> > On Fri, Sep 12, 2014 at 09:08:08AM -0400, Ashwin Chaugule wrote:
> >> On 10 September 2014 13:20, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote:
> >
> >> How does this version look? If there are no more changes, please let
> >> me know which tree this can be picked by and I can send a pull request
> >> if that is preferred for this single patch.
> >
> > Please allow a reasonable time for review - you're nagging after two
> > days, this is unreasonable for something that isn't super urgent.  Two
> > weeks would be more reasonable.  As things stand you're adding to the
> > mail volume and some people will actively delay looking at things in
> > order to avoid encouraging such behaviour.
> 
> I apologize if it seems that way. I very much appreciate the help I've
> received so far. I'd sent V6 9 days ago and only Lv had feedback
> around cosmetic changes. Given the simplicity of this patch and all
> the previous suggestions, it seemed like we're nearly done with the
> reviews. I understand your point though and look forward to seeing
> this patch progress.

It looks this line is still wrong:
+	return ACPI_SUCCESS(status) ? -EINVAL : 0;
You may need to run a test to validate the revised patch.

Thanks and best regards
-Lv

Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Mark Brown]

[-- Attachment #1: Type: text/plain, Size: 1118 bytes --]

On Wed, Sep 10, 2014 at 01:20:18PM -0400, Ashwin Chaugule wrote:

> ACPI 5.0+ spec defines a generic mode of communication
> between the OS and a platform such as the BMC. This medium
> (PCC) is typically used by CPPC (ACPI CPU Performance management),
> RAS (ACPI reliability protocol) and MPST (ACPI Memory power
> states).

This mostly looks good to me at a fairly high level, one small nit below
which I don't think should be a blocker to an initial merge but would be
good to fix.

Reviewed-by: Mark Brown <broonie@kernel.org>

> +static bool pcc_tx_done(struct mbox_chan *chan)
> +{
> +	struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
> +	struct acpi_pcct_shared_memory *generic_comm_base =
> +		(struct acpi_pcct_shared_memory *) pcct_ss->base_address;
> +	u16 cmd_delay = pcct_ss->min_turnaround_time;
> +
> +	/* Wait for Platform to consume. */
> +	while (!(readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE))
> +		udelay(cmd_delay);

This will busy wait for ever if the controller dies.  We're in big
trouble if that happens but it would be good to have some sort of
timeout and scream here.

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Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Ashwin Chaugule]

Hi Lv,

On 16 September 2014 00:38, Zheng, Lv <lv.zheng@intel.com> wrote:

>
> It looks this line is still wrong:
> +       return ACPI_SUCCESS(status) ? -EINVAL : 0;
> You may need to run a test to validate the revised patch.

You're right, I should either use ACPI_FAILURE or swap -EINVAL and 0.

Cheers,
Ashwin

Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Ashwin Chaugule]

Hi Mark,

On 16 September 2014 13:40, Mark Brown <broonie@kernel.org> wrote:
> On Wed, Sep 10, 2014 at 01:20:18PM -0400, Ashwin Chaugule wrote:
>
>> ACPI 5.0+ spec defines a generic mode of communication
>> between the OS and a platform such as the BMC. This medium
>> (PCC) is typically used by CPPC (ACPI CPU Performance management),
>> RAS (ACPI reliability protocol) and MPST (ACPI Memory power
>> states).
>
> This mostly looks good to me at a fairly high level, one small nit below
> which I don't think should be a blocker to an initial merge but would be
> good to fix.
>
> Reviewed-by: Mark Brown <broonie@kernel.org>

Much appreciated!

>
>> +static bool pcc_tx_done(struct mbox_chan *chan)
>> +{
>> +     struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
>> +     struct acpi_pcct_shared_memory *generic_comm_base =
>> +             (struct acpi_pcct_shared_memory *) pcct_ss->base_address;
>> +     u16 cmd_delay = pcct_ss->min_turnaround_time;
>> +
>> +     /* Wait for Platform to consume. */
>> +     while (!(readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE))
>> +             udelay(cmd_delay);
>
> This will busy wait for ever if the controller dies.  We're in big
> trouble if that happens but it would be good to have some sort of
> timeout and scream here.

Agreed. I'll add this along with Lv's feedback.

Cheers,
Ashwin

Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Ashwin Chaugule]

On 16 September 2014 14:28, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote:
> Hi Mark,
>
> On 16 September 2014 13:40, Mark Brown <broonie@kernel.org> wrote:
>> On Wed, Sep 10, 2014 at 01:20:18PM -0400, Ashwin Chaugule wrote:
>>
>>> ACPI 5.0+ spec defines a generic mode of communication
>>> between the OS and a platform such as the BMC. This medium
>>> (PCC) is typically used by CPPC (ACPI CPU Performance management),
>>> RAS (ACPI reliability protocol) and MPST (ACPI Memory power
>>> states).
>>
>> This mostly looks good to me at a fairly high level, one small nit below
>> which I don't think should be a blocker to an initial merge but would be
>> good to fix.
>>
>> Reviewed-by: Mark Brown <broonie@kernel.org>
>
> Much appreciated!
>
>>
>>> +static bool pcc_tx_done(struct mbox_chan *chan)
>>> +{
>>> +     struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
>>> +     struct acpi_pcct_shared_memory *generic_comm_base =
>>> +             (struct acpi_pcct_shared_memory *) pcct_ss->base_address;
>>> +     u16 cmd_delay = pcct_ss->min_turnaround_time;
>>> +
>>> +     /* Wait for Platform to consume. */
>>> +     while (!(readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE))
>>> +             udelay(cmd_delay);
>>
>> This will busy wait for ever if the controller dies.  We're in big
>> trouble if that happens but it would be good to have some sort of
>> timeout and scream here.
>
> Agreed. I'll add this along with Lv's feedback.


How about something like this?

--------8<-------------
-
-       /* Wait for Platform to consume. */
-       while (!(readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE))
-               udelay(cmd_delay);
-
+       unsigned int retries = 0;
+
+       /* Try a few times while waiting for platform to consume */
+       while (!(readw_relaxed(&generic_comm_base->status) &
PCC_CMD_COMPLETE)) {
+               if (retries++ < 5)
+                       udelay(cmd_delay);
+               else {
+                       pr_err("PCC platform did not respond.\n");
+                       return false;
+               }
+       }

--------8<-------------

And the Mbox client additionally sets .tx_block = true and .tx_out =
10(msecs). That way, if the remote hangs or crashes, the
wait_for_completion in the controller code timesout and sends an -EIO
to the client .tx_done method so it knows something went wrong.

Thanks,
Ashwin

Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Mark Brown]

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On Wed, Sep 17, 2014 at 06:17:03PM -0400, Ashwin Chaugule wrote:

> +       while (!(readw_relaxed(&generic_comm_base->status) &
> PCC_CMD_COMPLETE)) {
> +               if (retries++ < 5)
> +                       udelay(cmd_delay);
> +               else {
> +                       pr_err("PCC platform did not respond.\n");
> +                       return false;
> +               }
> +       }

You should have { } on both branches of the if but otherwise that looks
fine to me (assuming that there are enough retries).

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Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Ashwin Chaugule]

Hi Mark,

On 17 September 2014 18:17, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote:
> On 16 September 2014 14:28, Ashwin Chaugule <ashwin.chaugule@linaro.org> wrote:
>> Hi Mark,
>>
>> On 16 September 2014 13:40, Mark Brown <broonie@kernel.org> wrote:
>>> On Wed, Sep 10, 2014 at 01:20:18PM -0400, Ashwin Chaugule wrote:
>>>
>>>> ACPI 5.0+ spec defines a generic mode of communication
>>>> between the OS and a platform such as the BMC. This medium
>>>> (PCC) is typically used by CPPC (ACPI CPU Performance management),
>>>> RAS (ACPI reliability protocol) and MPST (ACPI Memory power
>>>> states).
>>>
>>> This mostly looks good to me at a fairly high level, one small nit below
>>> which I don't think should be a blocker to an initial merge but would be
>>> good to fix.
>>>
>>> Reviewed-by: Mark Brown <broonie@kernel.org>
>>
>> Much appreciated!
>>
>>>
>>>> +static bool pcc_tx_done(struct mbox_chan *chan)
>>>> +{
>>>> +     struct acpi_pcct_subspace *pcct_ss = chan->con_priv;
>>>> +     struct acpi_pcct_shared_memory *generic_comm_base =
>>>> +             (struct acpi_pcct_shared_memory *) pcct_ss->base_address;
>>>> +     u16 cmd_delay = pcct_ss->min_turnaround_time;
>>>> +
>>>> +     /* Wait for Platform to consume. */
>>>> +     while (!(readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE))
>>>> +             udelay(cmd_delay);
>>>
>>> This will busy wait for ever if the controller dies.  We're in big
>>> trouble if that happens but it would be good to have some sort of
>>> timeout and scream here.
>>
>> Agreed. I'll add this along with Lv's feedback.
>
>
> How about something like this?
>
> --------8<-------------
> -
> -       /* Wait for Platform to consume. */
> -       while (!(readw_relaxed(&generic_comm_base->status) & PCC_CMD_COMPLETE))
> -               udelay(cmd_delay);
> -
> +       unsigned int retries = 0;
> +
> +       /* Try a few times while waiting for platform to consume */
> +       while (!(readw_relaxed(&generic_comm_base->status) &
> PCC_CMD_COMPLETE)) {
> +               if (retries++ < 5)
> +                       udelay(cmd_delay);
> +               else {
> +                       pr_err("PCC platform did not respond.\n");
> +                       return false;
> +               }
> +       }
>
> --------8<-------------
>
> And the Mbox client additionally sets .tx_block = true and .tx_out =
> 10(msecs). That way, if the remote hangs or crashes, the
> wait_for_completion in the controller code timesout and sends an -EIO
> to the client .tx_done method so it knows something went wrong.

Can I add the above snippet to V8 with your Reviewed-by tag?

Thanks,
Ashwin

Re: [PATCH v7 1/2] Mailbox: Add support for Platform Communication Channel

[Mark Brown]

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On Tue, Sep 30, 2014 at 01:23:30PM -0400, Ashwin Chaugule wrote:

> Can I add the above snippet to V8 with your Reviewed-by tag?

Post the new code and I'll review that.

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