mfd: db8500-prcmu: Support U8420-sysclk firmware

There is a distinct version of the Ux500 U8420 variant
with "sysclk", as can be seen from the vendor code that
didn't make it upstream, this firmware lacks the
ULPPLL (ultra-low power phase locked loop) which in
effect means that the timer clock is instead wired to
the 32768 Hz always-on clock.

This has some repercussions when enabling the timer
clock as the code as it stands will disable the timer
clock on these platforms (lacking the so-called
"doze mode") and obtaining the wrong rate of the timer
clock.

The timer frequency is of course needed very early in
the boot, and as a consequence, we need to shuffle
around the early PRCMU init code: whereas in the past
we did not need to look up the PRCMU firmware version
in the early init, but now we need to know the version
before the core system timers are registered so we
restructure the platform callbacks to the PRCMU so as
not to take any arguments and instead look up the
resources it needs directly from the device tree
when initializing.

As we do not yet support any platforms using this
firmware it is not a regression, but as PostmarketOS
is starting to support products with this firmware we
need to fix this up.

The low rate of 32kHz also makes the MTU timer unsuitable
as delay timer but this needs to be fixed in a separate
patch.

Signed-off-by: Linus Walleij <[email protected]>
Reviewed-by: Stephan Gerhold <[email protected]>
Acked-by: Olof Johansson <[email protected]>
Signed-off-by: Lee Jones <[email protected]>

Author: linusw

arch/arm/mach-ux500/cpu-db8500.c

@@ -84,14 +84,14 @@ static void __init ux500_init_irq(void)
 	struct resource r;
 
 	irqchip_init();
+	prcmu_early_init();
 	np = of_find_compatible_node(NULL, NULL, "stericsson,db8500-prcmu");
 	of_address_to_resource(np, 0, &r);
 	of_node_put(np);
 	if (!r.start) {
 		pr_err("could not find PRCMU base resource\n");
 		return;
 	}
-	prcmu_early_init(r.start, r.end-r.start);
 	ux500_pm_init(r.start, r.end-r.start);
 
 	/* Unlock before init */

drivers/mfd/db8500-prcmu.c

@@ -27,6 +27,7 @@
 #include <linux/bitops.h>
 #include <linux/fs.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
 #include <linux/of_irq.h>
 #include <linux/platform_device.h>
 #include <linux/uaccess.h>
@@ -668,6 +669,14 @@ struct prcmu_fw_version *prcmu_get_fw_version(void)
 	return fw_info.valid ? &fw_info.version : NULL;
 }
 
+static bool prcmu_is_ulppll_disabled(void)
+{
+	struct prcmu_fw_version *ver;
+
+	ver = prcmu_get_fw_version();
+	return ver && ver->project == PRCMU_FW_PROJECT_U8420_SYSCLK;
+}
+
 bool prcmu_has_arm_maxopp(void)
 {
 	return (readb(tcdm_base + PRCM_AVS_VARM_MAX_OPP) &
@@ -1308,10 +1317,23 @@ static int request_sysclk(bool enable)
 
 static int request_timclk(bool enable)
 {
-	u32 val = (PRCM_TCR_DOZE_MODE | PRCM_TCR_TENSEL_MASK);
+	u32 val;
+
+	/*
+	 * On the U8420_CLKSEL firmware, the ULP (Ultra Low Power)
+	 * PLL is disabled so we cannot use doze mode, this will
+	 * stop the clock on this firmware.
+	 */
+	if (prcmu_is_ulppll_disabled())
+		val = 0;
+	else
+		val = (PRCM_TCR_DOZE_MODE | PRCM_TCR_TENSEL_MASK);
 
 	if (!enable)
-		val |= PRCM_TCR_STOP_TIMERS;
+		val |= PRCM_TCR_STOP_TIMERS |
+			PRCM_TCR_DOZE_MODE |
+			PRCM_TCR_TENSEL_MASK;
+
 	writel(val, PRCM_TCR);
 
 	return 0;
@@ -1615,7 +1637,8 @@ unsigned long prcmu_clock_rate(u8 clock)
 	if (clock < PRCMU_NUM_REG_CLOCKS)
 		return clock_rate(clock);
 	else if (clock == PRCMU_TIMCLK)
-		return ROOT_CLOCK_RATE / 16;
+		return prcmu_is_ulppll_disabled() ?
+			32768 : ROOT_CLOCK_RATE / 16;
 	else if (clock == PRCMU_SYSCLK)
 		return ROOT_CLOCK_RATE;
 	else if (clock == PRCMU_PLLSOC0)
@@ -2646,6 +2669,8 @@ static char *fw_project_name(u32 project)
 		return "U8520 MBL";
 	case PRCMU_FW_PROJECT_U8420:
 		return "U8420";
+	case PRCMU_FW_PROJECT_U8420_SYSCLK:
+		return "U8420-sysclk";
 	case PRCMU_FW_PROJECT_U9540:
 		return "U9540";
 	case PRCMU_FW_PROJECT_A9420:
@@ -2693,27 +2718,18 @@ static int db8500_irq_init(struct device_node *np)
 	return 0;
 }
 
-static void dbx500_fw_version_init(struct platform_device *pdev,
-			    u32 version_offset)
+static void dbx500_fw_version_init(struct device_node *np)
 {
-	struct resource *res;
 	void __iomem *tcpm_base;
 	u32 version;
 
-	res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
-					   "prcmu-tcpm");
-	if (!res) {
-		dev_err(&pdev->dev,
-			"Error: no prcmu tcpm memory region provided\n");
-		return;
-	}
-	tcpm_base = ioremap(res->start, resource_size(res));
+	tcpm_base = of_iomap(np, 1);
 	if (!tcpm_base) {
-		dev_err(&pdev->dev, "no prcmu tcpm mem region provided\n");
+		pr_err("no prcmu tcpm mem region provided\n");
 		return;
 	}
 
-	version = readl(tcpm_base + version_offset);
+	version = readl(tcpm_base + DB8500_PRCMU_FW_VERSION_OFFSET);
 	fw_info.version.project = (version & 0xFF);
 	fw_info.version.api_version = (version >> 8) & 0xFF;
 	fw_info.version.func_version = (version >> 16) & 0xFF;
@@ -2731,7 +2747,7 @@ static void dbx500_fw_version_init(struct platform_device *pdev,
 	iounmap(tcpm_base);
 }
 
-void __init db8500_prcmu_early_init(u32 phy_base, u32 size)
+void __init db8500_prcmu_early_init(void)
 {
 	/*
 	 * This is a temporary remap to bring up the clocks. It is
@@ -2740,9 +2756,17 @@ void __init db8500_prcmu_early_init(u32 phy_base, u32 size)
 	 * clock driver can probe independently. An early initcall will
 	 * still be needed, but it can be diverted into drivers/clk/ux500.
 	 */
-	prcmu_base = ioremap(phy_base, size);
-	if (!prcmu_base)
+	struct device_node *np;
+
+	np = of_find_compatible_node(NULL, NULL, "stericsson,db8500-prcmu");
+	prcmu_base = of_iomap(np, 0);
+	if (!prcmu_base) {
+		of_node_put(np);
 		pr_err("%s: ioremap() of prcmu registers failed!\n", __func__);
+		return;
+	}
+	dbx500_fw_version_init(np);
+	of_node_put(np);
 
 	spin_lock_init(&mb0_transfer.lock);
 	spin_lock_init(&mb0_transfer.dbb_irqs_lock);
@@ -3084,7 +3108,6 @@ static int db8500_prcmu_probe(struct platform_device *pdev)
 		return -ENOMEM;
 	}
 	init_prcm_registers();
-	dbx500_fw_version_init(pdev, DB8500_PRCMU_FW_VERSION_OFFSET);
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "prcmu-tcdm");
 	if (!res) {
 		dev_err(&pdev->dev, "no prcmu tcdm region provided\n");

include/linux/mfd/db8500-prcmu.h

@@ -489,7 +489,7 @@ struct prcmu_auto_pm_config {
 
 #ifdef CONFIG_MFD_DB8500_PRCMU
 
-void db8500_prcmu_early_init(u32 phy_base, u32 size);
+void db8500_prcmu_early_init(void);
 int prcmu_set_rc_a2p(enum romcode_write);
 enum romcode_read prcmu_get_rc_p2a(void);
 enum ap_pwrst prcmu_get_xp70_current_state(void);
@@ -546,7 +546,7 @@ void db8500_prcmu_write_masked(unsigned int reg, u32 mask, u32 value);
 
 #else /* !CONFIG_MFD_DB8500_PRCMU */
 
-static inline void db8500_prcmu_early_init(u32 phy_base, u32 size) {}
+static inline void db8500_prcmu_early_init(void) {}
 
 static inline int prcmu_set_rc_a2p(enum romcode_write code)
 {

include/linux/mfd/dbx500-prcmu.h

@@ -190,6 +190,7 @@ enum ddr_pwrst {
 #define PRCMU_FW_PROJECT_U8500_MBL2	12 /* Customer specific */
 #define PRCMU_FW_PROJECT_U8520		13
 #define PRCMU_FW_PROJECT_U8420		14
+#define PRCMU_FW_PROJECT_U8420_SYSCLK	17
 #define PRCMU_FW_PROJECT_A9420		20
 /* [32..63] 9540 and derivatives */
 #define PRCMU_FW_PROJECT_U9540		32
@@ -211,9 +212,9 @@ struct prcmu_fw_version {
 
 #if defined(CONFIG_UX500_SOC_DB8500)
 
-static inline void prcmu_early_init(u32 phy_base, u32 size)
+static inline void prcmu_early_init(void)
 {
-	return db8500_prcmu_early_init(phy_base, size);
+	return db8500_prcmu_early_init();
 }
 
 static inline int prcmu_set_power_state(u8 state, bool keep_ulp_clk,
@@ -401,7 +402,7 @@ static inline int prcmu_config_a9wdog(u8 num, bool sleep_auto_off)
 }
 #else
 
-static inline void prcmu_early_init(u32 phy_base, u32 size) {}
+static inline void prcmu_early_init(void) {}
 
 static inline int prcmu_set_power_state(u8 state, bool keep_ulp_clk,
 	bool keep_ap_pll)