OMAP: I2C: PM: Adapt to pm_qos framework for requesting mpu lat

This patch adapts PM_QoS infrastructure to request MPU latency.
PM_QoS provides interface for drivers to register  performance
expectations such as in this case, MPU wakeup latency.

The current I2C driver uses a wrapper around PM_QoS interface to
request MPU latency.
The resultant behavior was as follows:
when ever any i2c transaction took place, every i2c request translates
into individual i2c_xfers. Each i2c_xfer in the current I2C driver
does the following:
 allocate memory for a pm_qos request
 request the qos latency
 do things that are time critical
 remove the qos request
 free the memory

Instead, it is possible to make this efficient by:
Allocating, adding the request on probe (with the default as disabled),
removing the request and freeing the allocated memory on remove.
In i2c_xfer, we can do:
  update the request with required latency
  do time critical operation
  update the request with default latency to disable the request.

This allows the system to optimize the time critical i2c_xfer path
which all drivers which use i2c will use.

Acked-by: Todd Poyner <toddpoynor@google.com>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Girish S G <girishsg@ti.com>

1 files changed, 35 insertions, 12 deletions

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index ab9833b..da986f2 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -40,6 +40,7 @@
 #include <linux/slab.h>
 #include <linux/i2c-omap.h>
 #include <linux/pm_runtime.h>
+#include <linux/pm_qos_params.h>
 
 /* I2C controller revisions */
 #define OMAP_I2C_REV_2			0x20
@@ -179,8 +180,7 @@ struct omap_i2c_dev {
 	struct completion	cmd_complete;
 	struct resource		*ioarea;
 	u32			latency;	/* maximum mpu wkup latency */
-	void			(*set_mpu_wkup_lat)(struct device *dev,
-						    long latency);
+	struct pm_qos_request_list *pm_qos;
 	u32			speed;		/* Speed of bus in Khz */
 	u16			cmd_err;
 	u8			*buf;
@@ -648,8 +648,14 @@ omap_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 	if (r < 0)
 		goto out;
 
-	if (dev->set_mpu_wkup_lat != NULL)
-		dev->set_mpu_wkup_lat(dev->dev, dev->latency);
+	/*
+	 * When waiting for completion of a i2c transfer, we need to
+	 * set a wake up latency constraint for the MPU. This is to
+	 * ensure quick enough wakeup from idle, when transfer
+	 * completes.
+	 */
+	if (dev->pm_qos)
+		pm_qos_update_request(dev->pm_qos, dev->latency);
 
 	for (i = 0; i < num; i++) {
 		r = omap_i2c_xfer_msg(adap, &msgs[i], (i == (num - 1)));
@@ -657,8 +663,8 @@ omap_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 			break;
 	}
 
-	if (dev->set_mpu_wkup_lat != NULL)
-		dev->set_mpu_wkup_lat(dev->dev, -1);
+	if (dev->pm_qos)
+		pm_qos_update_request(dev->pm_qos, PM_QOS_DEFAULT_VALUE);
 
 	if (r == 0)
 		r = num;
@@ -1007,13 +1013,10 @@ omap_i2c_probe(struct platform_device *pdev)
 		goto err_release_region;
 	}
 
-	if (pdata != NULL) {
+	if (pdata)
 		speed = pdata->clkrate;
-		dev->set_mpu_wkup_lat = pdata->set_mpu_wkup_lat;
-	} else {
+	else
 		speed = 100;	/* Default speed */
-		dev->set_mpu_wkup_lat = NULL;
-	}
 
 	dev->speed = speed;
 	dev->idle = 1;
@@ -1025,6 +1028,17 @@ omap_i2c_probe(struct platform_device *pdev)
 		goto err_free_mem;
 	}
 
+	if (pdata && pdata->needs_wakeup_latency) {
+		dev->pm_qos = kzalloc(sizeof(struct pm_qos_request_list),
+					GFP_KERNEL);
+		if (!dev->pm_qos) {
+			r = -ENOMEM;
+			goto err_unmap;
+		}
+		pm_qos_add_request(dev->pm_qos, PM_QOS_CPU_DMA_LATENCY,
+					PM_QOS_DEFAULT_VALUE);
+	}
+
 	platform_set_drvdata(pdev, dev);
 
 	if (cpu_is_omap7xx())
@@ -1067,7 +1081,7 @@ omap_i2c_probe(struct platform_device *pdev)
 			dev->b_hw = 1; /* Enable hardware fixes */
 		}
 		/* calculate wakeup latency constraint for MPU */
-		if (dev->set_mpu_wkup_lat != NULL)
+		if (dev->pm_qos)
 			dev->latency = (1000000 * dev->fifo_size) /
 				       (1000 * speed / 8);
 	}
@@ -1111,6 +1125,11 @@ err_free_irq:
 err_unuse_clocks:
 	omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, 0);
 	omap_i2c_idle(dev);
+	if (dev->pm_qos) {
+		pm_qos_remove_request(dev->pm_qos);
+		kfree(dev->pm_qos);
+	}
+err_unmap:
 	iounmap(dev->base);
 err_free_mem:
 	platform_set_drvdata(pdev, NULL);
@@ -1133,6 +1152,10 @@ omap_i2c_remove(struct platform_device *pdev)
 	i2c_del_adapter(&dev->adapter);
 	omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, 0);
 	iounmap(dev->base);
+	if (dev->pm_qos) {
+		pm_qos_remove_request(dev->pm_qos);
+		kfree(dev->pm_qos);
+	}
 	kfree(dev);
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	release_mem_region(mem->start, resource_size(mem));