[PATCH v2] renesas: Renesas R-Car Gen4 watchdog driver
Shmuel Melamud via B4 Relay
devnull+smelamud.redhat.com at kernel.org
Fri May 30 00:58:57 CEST 2025
From: Shmuel Melamud <smelamud at redhat.com>
Add support of Renesas R-Car Gen4 watchdog timer. Timeouts up to
8184.0s are supported (CKS1 register is not involved). The watchdog
uses the clock type CLK_TYPE_GEN4_MDSEL, so handling of this constant
is added to gen3_clk_get_rate64() function.
The timeout is set in
dts/upstream/src/arm64/renesas/r8a779f0-spider-cpu.dtsi section &rwdt.
This patch was tested on real Renesas R8A779F0 hardware. If the watchdog
driver is enabled at the build time, the watchdog timer is initialized
when U-Boot starts. Under normal circumstances, U-Boot loads the kernel,
it starts systemd and systemd continues to pet the watchdog. If systemd
is not started before the timeout expires, the watchdog resets the
board.
Signed-off-by: Shmuel Leib Melamud <smelamud at redhat.com>
---
drivers/clk/renesas/clk-rcar-gen3.c | 4 +-
drivers/watchdog/Kconfig | 8 ++
drivers/watchdog/Makefile | 1 +
drivers/watchdog/renesas_wdt.c | 172 ++++++++++++++++++++++++++++++++++++
4 files changed, 184 insertions(+), 1 deletion(-)
diff --git a/drivers/clk/renesas/clk-rcar-gen3.c b/drivers/clk/renesas/clk-rcar-gen3.c
index 375cc4a4930873ad0d5509c19ad04a0ea5545aa0..5745acf4023c9114f6fa13b5e4baa306c5b57d33 100644
--- a/drivers/clk/renesas/clk-rcar-gen3.c
+++ b/drivers/clk/renesas/clk-rcar-gen3.c
@@ -68,7 +68,7 @@ static int gen3_clk_get_parent(struct gen3_clk_priv *priv, struct clk *clk,
if (ret)
return ret;
- if (core->type == CLK_TYPE_GEN3_MDSEL) {
+ if (core->type == CLK_TYPE_GEN3_MDSEL || core->type == CLK_TYPE_GEN4_MDSEL) {
shift = priv->cpg_mode & BIT(core->offset) ? 0 : 16;
parent->dev = clk->dev;
parent->id = core->parent >> shift;
@@ -318,6 +318,8 @@ static u64 gen3_clk_get_rate64(struct clk *clk)
"FIXED");
case CLK_TYPE_GEN3_MDSEL:
+ fallthrough;
+ case CLK_TYPE_GEN4_MDSEL:
shift = priv->cpg_mode & BIT(core->offset) ? 0 : 16;
div = (core->div >> shift) & 0xffff;
rate = gen3_clk_get_rate64(&parent) / div;
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 1bb67f5035231df9f6ce01adb08d074855393143..a0f2948335f9c3b74b7823f039e578ff4030e97c 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -335,6 +335,14 @@ config WDT_K3_RTI_FW_FILE
endif
+config WDT_RENESAS
+ bool "Renesas watchdog timer support"
+ depends on WDT && R8A779F0
+ select CLK
+ select CLK_RENESAS
+ help
+ Enables Renesas SoC R8A779F0 watchdog timer support.
+
config WDT_SANDBOX
bool "Enable Watchdog Timer support for Sandbox"
depends on SANDBOX && WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index e6bd4c587af6133c405dde6dbada8050debc781c..c4467d6e126d0c3e119bf8014b302e5b1432f541 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -43,6 +43,7 @@ obj-$(CONFIG_WDT_MTK) += mtk_wdt.o
obj-$(CONFIG_WDT_NPCM) += npcm_wdt.o
obj-$(CONFIG_WDT_OCTEONTX) += octeontx_wdt.o
obj-$(CONFIG_WDT_OMAP3) += omap_wdt.o
+obj-$(CONFIG_WDT_RENESAS) += renesas_wdt.o
obj-$(CONFIG_WDT_SBSA) += sbsa_gwdt.o
obj-$(CONFIG_WDT_K3_RTI) += rti_wdt.o
obj-$(CONFIG_WDT_SIEMENS_PMIC) += siemens_pmic_wdt.o
diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
new file mode 100644
index 0000000000000000000000000000000000000000..97550794a2e7108ee63aa0011f55c8c0fa77adb9
--- /dev/null
+++ b/drivers/watchdog/renesas_wdt.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0+
+// Copyright 2025 Red Hat, Inc., Shmuel Leib Melamud <smelamud at redhat.com>
+
+#include <clk.h>
+#include <dm.h>
+#include <wdt.h>
+#include <asm/io.h>
+#include <dm/device_compat.h>
+#include <linux/delay.h>
+#include <linux/iopoll.h>
+
+#define usleep_range(a, b) udelay((b))
+
+struct renesas_wdt {
+ u32 cnt;
+ u32 csra;
+ u32 csrb;
+};
+
+#define RWTCSRA_WOVF BIT(4)
+#define RWTCSRA_WRFLG BIT(5)
+#define RWTCSRA_TME BIT(7)
+
+#define CSR_MASK 0xA5A5A500
+#define CNT_MASK 0x5A5A0000
+
+/*
+ * In probe, clk_rate is checked to be not more than 16 bit * biggest clock
+ * divider (12 bits). d is only a factor to fully utilize the WDT counter and
+ * will not exceed its 16 bits. Thus, no overflow, we stay below 32 bits.
+ */
+#define MUL_BY_CLKS_PER_SEC(p, d) \
+ DIV_ROUND_UP((d) * (p)->clk_rate, clk_divs[(p)->cks])
+
+/* d is 16 bit, clk_divs 12 bit -> no 32 bit overflow */
+#define DIV_BY_CLKS_PER_SEC(p, d) ((d) * clk_divs[(p)->cks] / (p)->clk_rate)
+
+static const unsigned int clk_divs[] = { 1, 4, 16, 32, 64, 128, 1024, 4096 };
+
+struct renesas_wdt_priv {
+ struct renesas_wdt __iomem *wdt;
+ unsigned long clk_rate;
+ u8 cks;
+ struct clk clk;
+};
+
+static void rwdt_wait_cycles(struct renesas_wdt_priv *priv, unsigned int cycles)
+{
+ unsigned int delay;
+
+ delay = DIV_ROUND_UP(cycles * 1000000, priv->clk_rate);
+
+ usleep_range(delay, 2 * delay);
+}
+
+static int renesas_wdt_start(struct udevice *dev, u64 timeout, ulong flags)
+{
+ struct renesas_wdt_priv *priv = dev_get_priv(dev);
+ u64 max_timeout;
+ u8 val;
+
+ max_timeout = DIV_BY_CLKS_PER_SEC(priv, 65536);
+ timeout = min(max_timeout, timeout / 1000);
+
+ /* Stop the timer before we modify any register */
+ val = readb_relaxed(&priv->wdt->csra) & ~RWTCSRA_TME;
+ writel_relaxed(val | CSR_MASK, &priv->wdt->csra);
+ /* Delay 2 cycles before setting watchdog counter */
+ rwdt_wait_cycles(priv, 2);
+
+ while (readb_relaxed(&priv->wdt->csra) & RWTCSRA_WRFLG)
+ cpu_relax();
+
+ writel_relaxed((65536 - MUL_BY_CLKS_PER_SEC(priv, timeout)) | CNT_MASK,
+ &priv->wdt->cnt);
+
+ writel_relaxed(priv->cks | RWTCSRA_TME | CSR_MASK, &priv->wdt->csra);
+
+ return 0;
+}
+
+static int renesas_wdt_stop(struct udevice *dev)
+{
+ struct renesas_wdt_priv *priv = dev_get_priv(dev);
+
+ writel_relaxed(priv->cks | CSR_MASK, &priv->wdt->csra);
+
+ return 0;
+}
+
+static int renesas_wdt_reset(struct udevice *dev)
+{
+ struct renesas_wdt_priv *priv = dev_get_priv(dev);
+ u8 val;
+
+ /* Stop the timer before we modify any register */
+ val = readb_relaxed(&priv->wdt->csra) & ~RWTCSRA_TME;
+ writel_relaxed(val | CSR_MASK, &priv->wdt->csra);
+ /* Delay 2 cycles before setting watchdog counter */
+ rwdt_wait_cycles(priv, 2);
+
+ writel_relaxed(0xffff | CNT_MASK, &priv->wdt->cnt);
+ /* smallest divider to reboot soon */
+ writel_relaxed(0 | CSR_MASK, &priv->wdt->csra);
+
+ readb_poll_timeout(&priv->wdt->csra, val, !(val & RWTCSRA_WRFLG), 100);
+
+ writel_relaxed(RWTCSRA_TME | CSR_MASK, &priv->wdt->csra);
+
+ /* wait 2 cycles, so watchdog will trigger */
+ rwdt_wait_cycles(priv, 2);
+
+ return 0;
+}
+
+static int renesas_wdt_probe(struct udevice *dev)
+{
+ struct renesas_wdt_priv *priv = dev_get_priv(dev);
+ unsigned long clks_per_sec;
+ int ret, i;
+
+ priv->wdt = dev_remap_addr(dev);
+ if (!priv->wdt)
+ return -EINVAL;
+
+ ret = clk_get_by_index(dev, 0, &priv->clk);
+ if (ret < 0)
+ return ret;
+
+ ret = clk_enable(&priv->clk);
+ if (ret)
+ return ret;
+
+ priv->clk_rate = clk_get_rate(&priv->clk);
+ if (!priv->clk_rate)
+ return -ENOENT;
+
+ for (i = ARRAY_SIZE(clk_divs) - 1; i >= 0; i--) {
+ clks_per_sec = priv->clk_rate / clk_divs[i];
+ if (clks_per_sec && clks_per_sec < 65536) {
+ priv->cks = i;
+ break;
+ }
+ }
+
+ /* can't find a suitable clock divider */
+ if (i < 0)
+ return -ERANGE;
+
+ return 0;
+}
+
+static const struct wdt_ops renesas_wdt_ops = {
+ .start = renesas_wdt_start,
+ .reset = renesas_wdt_reset,
+ .stop = renesas_wdt_stop,
+};
+
+static const struct udevice_id renesas_wdt_ids[] = {
+ { .compatible = "renesas,r8a779f0-wdt" },
+ { .compatible = "renesas,rcar-gen4-wdt" },
+ {}
+};
+
+U_BOOT_DRIVER(wdt_renesas) = {
+ .name = "wdt_renesas",
+ .id = UCLASS_WDT,
+ .of_match = renesas_wdt_ids,
+ .ops = &renesas_wdt_ops,
+ .probe = renesas_wdt_probe,
+ .priv_auto = sizeof(struct renesas_wdt_priv),
+};
---
base-commit: 3b6760ddeb4ef940226921017cd9088c89784b01
change-id: 20250530-us-renesas-watchdog-2c79dbbd5cd2
Best regards,
--
Shmuel Leib Melamud <smelamud at redhat.com>
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