[RFC] pinctrl: pinctrl-imx: implement suspend/resume

[Stefan Agner]

In some SoC's using the IMX pin controller, the IP looses its state
when entering lowest power modes. Enhance the driver with suspend/
resume functions restoring the pin states.
---
Hi all,

Currently I'm working on implementing suspend-to-memory for Freescale
Vybrid (vf610) using the SoC's LPSTOP2 low power mode. One of the
issues I came across is that the IOMUXC module is also in the higher
power domain PD1 and hence looses its state during suspend.

I'm not sure if other SoC's behave similar and hence would benefit
from a generic implementation. At least i.MX6 seems not to power
gate the IOMUXC, at least this quote from the RM, chapter 10.4.2.3.3
"IO power reduction" lead me to believe that: 
> Digital IOs - Make sure all unnecessary PU/PD are disabled and IO
> are switched to either minimal drive strength or to input mode
> (when applicable)

If no other SoC is making use of it, its probably better to implement
it in the SoC specific code (e.g. pinctrl-vf610.c?) Although, currently
the mapped access to the registers is only locally available in
pinctrl-imx.c.

I'm also not sure if the suspend/resume functions are currently
early enough, at least the noirq family of suspend/resume functions
would be earlier. Hence if a device needs to have access to pins then,
we would restore them too late. Maybe syscore_ops would be more
appropriate?

Comments/ideas/advice appriciated...

--
Stefan

 drivers/pinctrl/freescale/pinctrl-imx.c   | 64 +++++++++++++++++++++++++++++++
 drivers/pinctrl/freescale/pinctrl-imx.h   |  3 ++
 drivers/pinctrl/freescale/pinctrl-vf610.c |  6 +++
 3 files changed, 73 insertions(+)

diff --git a/drivers/pinctrl/freescale/pinctrl-imx.c b/drivers/pinctrl/freescale/pinctrl-imx.c
index 448f109..0829098 100644
--- a/drivers/pinctrl/freescale/pinctrl-imx.c
+++ b/drivers/pinctrl/freescale/pinctrl-imx.c
@@ -23,6 +23,7 @@
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/pinctrl/pinmux.h>
 #include <linux/slab.h>
+#include <linux/syscore_ops.h>
 
 #include "../core.h"
 #include "pinctrl-imx.h"
@@ -40,6 +41,10 @@ struct imx_pinctrl {
 	struct pinctrl_dev *pctl;
 	void __iomem *base;
 	const struct imx_pinctrl_soc_info *info;
+#ifdef CONFIG_PM_SLEEP
+	u32 *mux_regs;
+	u32 *input_regs;
+#endif
 };
 
 static const inline struct imx_pin_group *imx_pinctrl_find_group_by_name(
@@ -640,6 +645,53 @@ static int imx_pinctrl_probe_dt(struct platform_device *pdev,
 	return 0;
 }
 
+static int __maybe_unused imx_pinctrl_suspend(struct device *dev)
+{
+	struct imx_pinctrl *ipctl = dev_get_drvdata(dev);
+	const struct imx_pinctrl_soc_info *info = ipctl->info;
+	int i;
+
+	for (i = 0; i < info->npins; i++) {
+		const struct imx_pin_reg *pin_reg = &info->pin_regs[i];
+		if (pin_reg->mux_reg == -1)
+			continue;
+
+		ipctl->mux_regs[i] = readl(ipctl->base + pin_reg->mux_reg);
+	}
+
+	for (i = 0; i < info->ninput_regs; i++)
+		ipctl->input_regs[i] = readl(ipctl->base +
+				info->input_regs_offset + i * sizeof(u32 *));
+
+	return 0;
+}
+
+static int __maybe_unused imx_pinctrl_resume(struct device *dev)
+{
+	struct imx_pinctrl *ipctl = dev_get_drvdata(dev);
+	const struct imx_pinctrl_soc_info *info = ipctl->info;
+	const struct imx_pin_reg *pin_reg;
+	int i;
+
+	for (i = 0; i < info->npins; i++) {
+		pin_reg = &info->pin_regs[i];
+		if (pin_reg->mux_reg == -1)
+			continue;
+
+		writel(ipctl->mux_regs[i], ipctl->base + pin_reg->mux_reg);
+	}
+
+	for (i = 0; i < info->ninput_regs; i++)
+		writel(ipctl->input_regs[i], ipctl->base +
+				info->input_regs_offset + i * sizeof(u32 *));
+
+	return 0;
+}
+
+const struct dev_pm_ops imx_pinctrl_dev_pm_ops = {
+	SET_LATE_SYSTEM_SLEEP_PM_OPS(imx_pinctrl_suspend, imx_pinctrl_resume)
+};
+
 int imx_pinctrl_probe(struct platform_device *pdev,
 		      struct imx_pinctrl_soc_info *info)
 {
@@ -664,6 +716,18 @@ int imx_pinctrl_probe(struct platform_device *pdev,
 		return -ENOMEM;
 	memset(info->pin_regs, 0xff, sizeof(*info->pin_regs) * info->npins);
 
+#ifdef CONFIG_PM_SLEEP
+	ipctl->mux_regs = devm_kzalloc(&pdev->dev, sizeof(u32 *) *
+				       info->npins, GFP_KERNEL);
+	if (!ipctl->mux_regs)
+		return -ENOMEM;
+
+	ipctl->input_regs = devm_kzalloc(&pdev->dev, sizeof(u32 *) *
+					 info->ninput_regs, GFP_KERNEL);
+	if (!ipctl->input_regs)
+		return -ENOMEM;
+#endif
+
 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	ipctl->base = devm_ioremap_resource(&pdev->dev, res);
 	if (IS_ERR(ipctl->base))
diff --git a/drivers/pinctrl/freescale/pinctrl-imx.h b/drivers/pinctrl/freescale/pinctrl-imx.h
index 49e55d3..6da6806 100644
--- a/drivers/pinctrl/freescale/pinctrl-imx.h
+++ b/drivers/pinctrl/freescale/pinctrl-imx.h
@@ -80,6 +80,8 @@ struct imx_pinctrl_soc_info {
 	unsigned int ngroups;
 	struct imx_pmx_func *functions;
 	unsigned int nfunctions;
+	unsigned int input_regs_offset;
+	unsigned int ninput_regs;
 	unsigned int flags;
 };
 
@@ -97,4 +99,5 @@ struct imx_pinctrl_soc_info {
 int imx_pinctrl_probe(struct platform_device *pdev,
 			struct imx_pinctrl_soc_info *info);
 int imx_pinctrl_remove(struct platform_device *pdev);
+extern const struct dev_pm_ops imx_pinctrl_dev_pm_ops;
 #endif /* __DRIVERS_PINCTRL_IMX_H */
diff --git a/drivers/pinctrl/freescale/pinctrl-vf610.c b/drivers/pinctrl/freescale/pinctrl-vf610.c
index fc86276..dbea076 100644
--- a/drivers/pinctrl/freescale/pinctrl-vf610.c
+++ b/drivers/pinctrl/freescale/pinctrl-vf610.c
@@ -19,6 +19,9 @@
 
 #include "pinctrl-imx.h"
 
+#define VF610_INPUT_REG_CNT		49
+#define VF610_INPUT_REG_BASE		0x2ec
+
 enum vf610_pads {
 	VF610_PAD_PTA6 = 0,
 	VF610_PAD_PTA8 = 1,
@@ -299,6 +302,8 @@ static const struct pinctrl_pin_desc vf610_pinctrl_pads[] = {
 static struct imx_pinctrl_soc_info vf610_pinctrl_info = {
 	.pins = vf610_pinctrl_pads,
 	.npins = ARRAY_SIZE(vf610_pinctrl_pads),
+	.input_regs_offset = VF610_INPUT_REG_BASE,
+	.ninput_regs = VF610_INPUT_REG_CNT,
 	.flags = SHARE_MUX_CONF_REG,
 };
 
@@ -316,6 +321,7 @@ static struct platform_driver vf610_pinctrl_driver = {
 	.driver = {
 		.name = "vf610-pinctrl",
 		.of_match_table = vf610_pinctrl_of_match,
+		.pm = &imx_pinctrl_dev_pm_ops,
 	},
 	.probe = vf610_pinctrl_probe,
 	.remove = imx_pinctrl_remove,
-- 
2.4.2