soc/tegra: pmc: Support systems where PMC is marked secure

On Tegra210 systems with new enough boot software, direct register
accesses to PMC register space from the non-secure world are not
allowed. Instead a monitor call may be used to read and write PMC
registers.

Add code to detect such a system by attempting to write a scratch
register and detecting if the write happened or not. If not, we switch
to doing all register accesses through the monitor call.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Jon Hunter <jonathanh@nvidia.com>

drivers/soc/tegra/pmc.c

@@ -20,6 +20,7 @@
 
 #define pr_fmt(fmt) "tegra-pmc: " fmt
 
+#include <linux/arm-smccc.h>
 #include <linux/clk.h>
 #include <linux/clk/tegra.h>
 #include <linux/debugfs.h>
@@ -145,6 +146,11 @@
 #define WAKE_AOWAKE_CTRL 0x4f4
 #define  WAKE_AOWAKE_CTRL_INTR_POLARITY BIT(0)
 
+/* for secure PMC */
+#define TEGRA_SMC_PMC		0xc2fffe00
+#define  TEGRA_SMC_PMC_READ	0xaa
+#define  TEGRA_SMC_PMC_WRITE	0xbb
+
 struct tegra_powergate {
 	struct generic_pm_domain genpd;
 	struct tegra_pmc *pmc;
@@ -216,6 +222,7 @@ struct tegra_pmc_soc {
 	bool has_gpu_clamps;
 	bool needs_mbist_war;
 	bool has_impl_33v_pwr;
+	bool maybe_tz_only;
 
 	const struct tegra_io_pad_soc *io_pads;
 	unsigned int num_io_pads;
@@ -278,6 +285,7 @@ static const char * const tegra30_reset_sources[] = {
  * @scratch: pointer to I/O remapped region for scratch registers
  * @clk: pointer to pclk clock
  * @soc: pointer to SoC data structure
+ * @tz_only: flag specifying if the PMC can only be accessed via TrustZone
  * @debugfs: pointer to debugfs entry
  * @rate: currently configured rate of pclk
  * @suspend_mode: lowest suspend mode available
@@ -308,6 +316,7 @@ struct tegra_pmc {
 	struct dentry *debugfs;
 
 	const struct tegra_pmc_soc *soc;
+	bool tz_only;
 
 	unsigned long rate;
 
@@ -346,13 +355,62 @@ to_powergate(struct generic_pm_domain *domain)
 
 static u32 tegra_pmc_readl(struct tegra_pmc *pmc, unsigned long offset)
 {
+	struct arm_smccc_res res;
+
+	if (pmc->tz_only) {
+		arm_smccc_smc(TEGRA_SMC_PMC, TEGRA_SMC_PMC_READ, offset, 0, 0,
+			      0, 0, 0, &res);
+		if (res.a0) {
+			if (pmc->dev)
+				dev_warn(pmc->dev, "%s(): SMC failed: %lu\n",
+					 __func__, res.a0);
+			else
+				pr_warn("%s(): SMC failed: %lu\n", __func__,
+					res.a0);
+		}
+
+		return res.a1;
+	}
+
 	return readl(pmc->base + offset);
 }
 
 static void tegra_pmc_writel(struct tegra_pmc *pmc, u32 value,
 			     unsigned long offset)
 {
-	writel(value, pmc->base + offset);
+	struct arm_smccc_res res;
+
+	if (pmc->tz_only) {
+		arm_smccc_smc(TEGRA_SMC_PMC, TEGRA_SMC_PMC_WRITE, offset,
+			      value, 0, 0, 0, 0, &res);
+		if (res.a0) {
+			if (pmc->dev)
+				dev_warn(pmc->dev, "%s(): SMC failed: %lu\n",
+					 __func__, res.a0);
+			else
+				pr_warn("%s(): SMC failed: %lu\n", __func__,
+					res.a0);
+		}
+	} else {
+		writel(value, pmc->base + offset);
+	}
+}
+
+static u32 tegra_pmc_scratch_readl(struct tegra_pmc *pmc, unsigned long offset)
+{
+	if (pmc->tz_only)
+		return tegra_pmc_readl(pmc, offset);
+
+	return readl(pmc->scratch + offset);
+}
+
+static void tegra_pmc_scratch_writel(struct tegra_pmc *pmc, u32 value,
+				     unsigned long offset)
+{
+	if (pmc->tz_only)
+		tegra_pmc_writel(pmc, value, offset);
+	else
+		writel(value, pmc->scratch + offset);
 }
 
 /*
@@ -776,7 +834,7 @@ static int tegra_pmc_restart_notify(struct notifier_block *this,
 	const char *cmd = data;
 	u32 value;
 
-	value = readl(pmc->scratch + pmc->soc->regs->scratch0);
+	value = tegra_pmc_scratch_readl(pmc, pmc->soc->regs->scratch0);
 	value &= ~PMC_SCRATCH0_MODE_MASK;
 
 	if (cmd) {
@@ -790,7 +848,7 @@ static int tegra_pmc_restart_notify(struct notifier_block *this,
 			value |= PMC_SCRATCH0_MODE_RCM;
 	}
 
-	writel(value, pmc->scratch + pmc->soc->regs->scratch0);
+	tegra_pmc_scratch_writel(pmc, value, pmc->soc->regs->scratch0);
 
 	/* reset everything but PMC_SCRATCH0 and PMC_RST_STATUS */
 	value = tegra_pmc_readl(pmc, PMC_CNTRL);
@@ -2071,6 +2129,7 @@ static const struct tegra_pmc_soc tegra20_pmc_soc = {
 	.has_gpu_clamps = false,
 	.needs_mbist_war = false,
 	.has_impl_33v_pwr = false,
+	.maybe_tz_only = false,
 	.num_io_pads = 0,
 	.io_pads = NULL,
 	.num_pin_descs = 0,
@@ -2117,6 +2176,7 @@ static const struct tegra_pmc_soc tegra30_pmc_soc = {
 	.has_gpu_clamps = false,
 	.needs_mbist_war = false,
 	.has_impl_33v_pwr = false,
+	.maybe_tz_only = false,
 	.num_io_pads = 0,
 	.io_pads = NULL,
 	.num_pin_descs = 0,
@@ -2167,6 +2227,7 @@ static const struct tegra_pmc_soc tegra114_pmc_soc = {
 	.has_gpu_clamps = false,
 	.needs_mbist_war = false,
 	.has_impl_33v_pwr = false,
+	.maybe_tz_only = false,
 	.num_io_pads = 0,
 	.io_pads = NULL,
 	.num_pin_descs = 0,
@@ -2277,6 +2338,7 @@ static const struct tegra_pmc_soc tegra124_pmc_soc = {
 	.has_gpu_clamps = true,
 	.needs_mbist_war = false,
 	.has_impl_33v_pwr = false,
+	.maybe_tz_only = false,
 	.num_io_pads = ARRAY_SIZE(tegra124_io_pads),
 	.io_pads = tegra124_io_pads,
 	.num_pin_descs = ARRAY_SIZE(tegra124_pin_descs),
@@ -2382,6 +2444,7 @@ static const struct tegra_pmc_soc tegra210_pmc_soc = {
 	.has_gpu_clamps = true,
 	.needs_mbist_war = true,
 	.has_impl_33v_pwr = false,
+	.maybe_tz_only = true,
 	.num_io_pads = ARRAY_SIZE(tegra210_io_pads),
 	.io_pads = tegra210_io_pads,
 	.num_pin_descs = ARRAY_SIZE(tegra210_pin_descs),
@@ -2506,6 +2569,7 @@ static const struct tegra_pmc_soc tegra186_pmc_soc = {
 	.has_gpu_clamps = false,
 	.needs_mbist_war = false,
 	.has_impl_33v_pwr = true,
+	.maybe_tz_only = false,
 	.num_io_pads = ARRAY_SIZE(tegra186_io_pads),
 	.io_pads = tegra186_io_pads,
 	.num_pin_descs = ARRAY_SIZE(tegra186_pin_descs),
@@ -2585,6 +2649,7 @@ static const struct tegra_pmc_soc tegra194_pmc_soc = {
 	.has_gpu_clamps = false,
 	.needs_mbist_war = false,
 	.has_impl_33v_pwr = false,
+	.maybe_tz_only = false,
 	.num_io_pads = ARRAY_SIZE(tegra194_io_pads),
 	.io_pads = tegra194_io_pads,
 	.regs = &tegra186_pmc_regs,
@@ -2619,6 +2684,32 @@ static struct platform_driver tegra_pmc_driver = {
 };
 builtin_platform_driver(tegra_pmc_driver);
 
+static bool __init tegra_pmc_detect_tz_only(struct tegra_pmc *pmc)
+{
+	u32 value, saved;
+
+	saved = readl(pmc->base + pmc->soc->regs->scratch0);
+	value = saved ^ 0xffffffff;
+
+	if (value == 0xffffffff)
+		value = 0xdeadbeef;
+
+	/* write pattern and read it back */
+	writel(value, pmc->base + pmc->soc->regs->scratch0);
+	value = readl(pmc->base + pmc->soc->regs->scratch0);
+
+	/* if we read all-zeroes, access is restricted to TZ only */
+	if (value == 0) {
+		pr_info("access to PMC is restricted to TZ\n");
+		return true;
+	}
+
+	/* restore original value */
+	writel(saved, pmc->base + pmc->soc->regs->scratch0);
+
+	return false;
+}
+
 /*
  * Early initialization to allow access to registers in the very early boot
  * process.
@@ -2681,6 +2772,9 @@ static int __init tegra_pmc_early_init(void)
 	if (np) {
 		pmc->soc = match->data;
 
+		if (pmc->soc->maybe_tz_only)
+			pmc->tz_only = tegra_pmc_detect_tz_only(pmc);
+
 		tegra_powergate_init(pmc, np);
 
 		/*