Re: [PATCH 3/4] watchdog: add meson secure watchdog driver

From: Xingyu Chen
Date: Mon Oct 14 2019 - 07:42:43 EST

Hi, Guenter
Thanks for your review.

On 2019/10/12 22:29, Guenter Roeck wrote:
On 10/12/19 3:05 AM, Xingyu Chen wrote:
The watchdog controller on the Meson-A/C series SoCs is moved to secure
world, watchdog operation needs to be done in secure EL3 mode via ATF,
Non-secure world can call SMC instruction to trap to AFT for watchdog
operation.

Signed-off-by: Xingyu Chen <xingyu.chen@xxxxxxxxxxx>
---
 drivers/watchdog/Kconfig | 16 +++
 drivers/watchdog/Makefile | 1 +
 drivers/watchdog/meson_sec_wdt.c | 205 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 222 insertions(+)
 create mode 100644 drivers/watchdog/meson_sec_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 58e7c10..e6b0707 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -826,6 +826,22 @@ config MESON_GXBB_WATCHDOG
ÂÂÂÂÂÂÂ To compile this driver as a module, choose M here: the
ÂÂÂÂÂÂÂ module will be called meson_gxbb_wdt.
+config MESON_SEC_WATCHDOG
+ÂÂÂ tristate "Amlogic Meson Secure watchdog support"
+ÂÂÂ depends on ARCH_MESON || COMPILE_TEST

Did you try COMPILE_TEST (eg allmodconfig) on, say x86_64 ?
AFAICS the meson sm calls are only available if MESON_SM is
enabled, and that depends on both ARCH_MESON and ARM64_4K_PAGES.
This dependency is not expressed here, and neither is enabled
with COMPILE_TEST.Sorry, I have't done this kind of test before for this patchset. There
is a kernel build error which related to the current driver when i try to use allmodconfig with x86. I will fix it by adding "depends on MESON_SM" in next version.

+ÂÂÂ select WATCHDOG_CORE
+ÂÂÂ help
+ÂÂÂÂÂ The watchdog controller on the Meson-A/C series SoCs is moved to
+ÂÂÂÂÂ secure world, watchdog operation needs to be done in secure EL3
+ÂÂÂÂÂ mode via ATF, non-secure world can call SMC instruction to trap
+ÂÂÂÂÂ to ATF for the watchdog operation.
+
+ÂÂÂÂÂ Say Y here if watchdog controller on Meson SoCs is located in
+ÂÂÂÂÂ secure world.
+
+ÂÂÂÂÂ To compile this driver as a module, choose M here: the
+ÂÂÂÂÂ module will be called meson_sec_wdt.
+
 config MESON_WATCHDOG
ÂÂÂÂÂ tristate "Amlogic Meson SoCs watchdog support"
ÂÂÂÂÂ depends on ARCH_MESON || COMPILE_TEST
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 2ee352b..5e6b73d 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -78,6 +78,7 @@ obj-$(CONFIG_QCOM_WDT) += qcom-wdt.o
 obj-$(CONFIG_BCM_KONA_WDT) += bcm_kona_wdt.o
 obj-$(CONFIG_TEGRA_WATCHDOG) += tegra_wdt.o
 obj-$(CONFIG_MESON_GXBB_WATCHDOG) += meson_gxbb_wdt.o
+obj-$(CONFIG_MESON_SEC_WATCHDOG) += meson_sec_wdt.o
 obj-$(CONFIG_MESON_WATCHDOG) += meson_wdt.o
 obj-$(CONFIG_MEDIATEK_WATCHDOG) += mtk_wdt.o
 obj-$(CONFIG_DIGICOLOR_WATCHDOG) += digicolor_wdt.o
diff --git a/drivers/watchdog/meson_sec_wdt.c b/drivers/watchdog/meson_sec_wdt.c
new file mode 100644
index 00000000..2b5357c
--- /dev/null
+++ b/drivers/watchdog/meson_sec_wdt.c
@@ -0,0 +1,205 @@
+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * Copyright (c) 2019 Amlogic, Inc. All rights reserved.
+ * Author: Xingyu Chen <xingyu.chen@xxxxxxxxxxx>
+ *
+ */
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+#include <linux/watchdog.h>
+#include <linux/firmware/meson/meson_sm.h>
+
+#define MESON_SIP_WDT_DISABLEÂÂÂÂÂÂÂ 0x1
+#define MESON_SIP_WDT_ENABLEÂÂÂÂÂÂÂ 0x2
+#define MESON_SIP_WDT_PINGÂÂÂÂÂÂÂ 0x3
+#define MESON_SIP_WDT_INITÂÂÂÂÂÂÂ 0x4
+#define MESON_SIP_WDT_RESETNOWÂÂÂÂÂÂÂ 0x5
+#define MESON_SIP_WDT_SETTIMEOUTÂÂÂ 0x6
+#define MESON_SIP_WDT_GETTIMELEFTÂÂÂ 0x7
+
+#define DEFAULT_TIMEOUTÂÂÂÂÂÂÂÂÂÂÂ 30 /* seconds */
+
+/*
+ * Watchdog timer tick is set to 1ms in secfw side, and tick count is
+ * stored in the bit[16-31] of WATCHDOG_CNT register, so the maximum
+ * timeout value is 0xffff ms.
+ */
+#define MAX_TIMEOUT_MSÂÂÂÂÂÂÂÂÂÂÂ 0xFFFF
+
+struct meson_sec_wdt {
+ÂÂÂ struct watchdog_device wdt_dev;
+ÂÂÂ struct meson_sm_firmware *fw;
+};
+
+static int meson_sec_wdt_start(struct watchdog_device *wdt_dev)
+{
+ÂÂÂ int ret;
+ÂÂÂ struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
+
+ÂÂÂ ret = meson_sm_call(data->fw, SM_WATCHDOG_OPS, NULL,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ MESON_SIP_WDT_ENABLE, 0, 0, 0, 0); > +ÂÂÂ if (ret)
+ÂÂÂÂÂÂÂ return ret;
+
+ÂÂÂ return 0;

This is equivalent to
ÂÂÂÂreturn ret;
or even
ÂÂÂÂreturn meson_sm_call(...);
I will fix it in next version.
+}
+
+static int meson_sec_wdt_stop(struct watchdog_device *wdt_dev)
+{
+ÂÂÂ int ret;
+ÂÂÂ struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
+
+ÂÂÂ ret = meson_sm_call(data->fw, SM_WATCHDOG_OPS, NULL,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ MESON_SIP_WDT_DISABLE, 0, 0, 0, 0);
+ÂÂÂ if (ret)
+ÂÂÂÂÂÂÂ return ret;
+
+ÂÂÂ return 0;

Same as above.
I will fix it in next version.

+}
+
+static int meson_sec_wdt_ping(struct watchdog_device *wdt_dev)
+{
+ÂÂÂ struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
+
+ÂÂÂ meson_sm_call(data->fw, SM_WATCHDOG_OPS, NULL,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂ MESON_SIP_WDT_PING, 0, 0, 0, 0);
+
+ÂÂÂ return 0;

Why ignore errors ?
I will fix it as above.

+}
+
+static int meson_sec_wdt_set_timeout(struct watchdog_device *wdt_dev,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ unsigned int timeout)
+{
+ÂÂÂ int ret;
+ÂÂÂ struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
+
+ÂÂÂ wdt_dev->timeout = timeout;
+ÂÂÂ meson_sec_wdt_ping(wdt_dev);
+

Unconditionally ? Also, the core does that after setting the timeoutIt is used to avoid watchdog timer expire once the timeout is updated,
and that the watchdog_ping from core not been invoked. If it is considered useless, i will remove it.


+ÂÂÂ ret = meson_sm_call(data->fw, SM_WATCHDOG_OPS, NULL,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ MESON_SIP_WDT_SETTIMEOUT,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ wdt_dev->timeout, 0, 0, 0);
+ÂÂÂ if (ret)
+ÂÂÂÂÂÂÂ return ret;
+
+ÂÂÂ return 0;

same as above.
I will fix it in next version.

+}
+
+static unsigned int meson_sec_wdt_get_timeleft(struct watchdog_device *wdt_dev)
+{
+ÂÂÂ int ret;
+ÂÂÂ int timeleft;
+ÂÂÂ struct meson_sec_wdt *data = watchdog_get_drvdata(wdt_dev);
+
+ÂÂÂ ret = meson_sm_call(data->fw, SM_WATCHDOG_OPS, &timeleft,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ MESON_SIP_WDT_GETTIMELEFT, 0, 0, 0, 0);
+
+ÂÂÂ if (ret)
+ÂÂÂÂÂÂÂ return 0;

Really ? Why ? 0 is most definitely incorrect here.
I just want to return a invalid value after I failed to get valid timeleft. Could you tell me what is corrent value ?

+
+ÂÂÂ return timeleft;
+}
+
+static const struct watchdog_ops meson_sec_wdt_ops = {
+ÂÂÂ .start = meson_sec_wdt_start,
+ÂÂÂ .stop = meson_sec_wdt_stop,
+ÂÂÂ .ping = meson_sec_wdt_ping,
+ÂÂÂ .set_timeout = meson_sec_wdt_set_timeout,
+ÂÂÂ .get_timeleft = meson_sec_wdt_get_timeleft,
+};
+
+static const struct watchdog_info meson_sec_wdt_info = {
+ÂÂÂ .identity = "Meson Secure Watchdog Timer",
+ÂÂÂ .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
+};
+
+static int __maybe_unused meson_sec_wdt_resume(struct device *dev)
+{
+ÂÂÂ struct meson_sec_wdt *data = dev_get_drvdata(dev);
+
+ÂÂÂ if (watchdog_active(&data->wdt_dev))
+ÂÂÂÂÂÂÂ meson_sec_wdt_start(&data->wdt_dev);

No error return ?
I will fix it in next version

+
+ÂÂÂ return 0;
+}
+
+static int __maybe_unused meson_sec_wdt_suspend(struct device *dev)
+{
+ÂÂÂ struct meson_sec_wdt *data = dev_get_drvdata(dev);
+
+ÂÂÂ if (watchdog_active(&data->wdt_dev))
+ÂÂÂÂÂÂÂ meson_sec_wdt_stop(&data->wdt_dev);

No error return ?
same as above

+
+ÂÂÂ return 0;
+}
+
+static const struct dev_pm_ops meson_sec_wdt_pm_ops = {
+ÂÂÂ SET_SYSTEM_SLEEP_PM_OPS(meson_sec_wdt_suspend, meson_sec_wdt_resume)
+};
+
+static const struct of_device_id meson_sec_wdt_dt_ids[] = {
+ÂÂÂÂ { .compatible = "amlogic,meson-sec-wdt", },
+ÂÂÂÂ { /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, meson_sec_wdt_dt_ids);
+
+static int meson_sec_wdt_probe(struct platform_device *pdev)
+{
+ÂÂÂ struct device *dev = &pdev->dev;
+ÂÂÂ struct meson_sec_wdt *data;
+ÂÂÂ struct device_node *sm_np;
+ÂÂÂ int ret;
+
+ÂÂÂ data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+ÂÂÂ if (!data)
+ÂÂÂÂÂÂÂ return -ENOMEM;
+
+ÂÂÂ sm_np = of_parse_phandle(pdev->dev.of_node, "secure-monitor", 0);
+ÂÂÂ if (!sm_np) {
+ÂÂÂÂÂÂÂ dev_err(&pdev->dev, "no secure-monitor node\n");
+ÂÂÂÂÂÂÂ return -ENODEV;

ENODEV is wrong here.
I found some drivers use the ENODEV in this case, Eg:
- ./watchdog/ts4800_wdt.c -122
- ./nvmem/meson-efuse.c -55
...

Could you tell me which error code is more suitable in this case ?


+ÂÂÂ }
+
+ÂÂÂ data->fw = meson_sm_get(sm_np);
+ÂÂÂ of_node_put(sm_np);
+ÂÂÂ if (!data->fw)
+ÂÂÂÂÂÂÂ return -EPROBE_DEFER;

How do you know ?
The fw pointer is static variable which is initialized to NULL. if it is equal to NULL, and indicate the meson_sm driver is not registered, then wdt driver use EPROBE_DEFER to defer probe.

+
+ÂÂÂ platform_set_drvdata(pdev, data);
+
+ÂÂÂ data->wdt_dev.parent = dev;
+ÂÂÂ data->wdt_dev.info = &meson_sec_wdt_info;
+ÂÂÂ data->wdt_dev.ops = &meson_sec_wdt_ops;
+ÂÂÂ data->wdt_dev.max_hw_heartbeat_ms = MAX_TIMEOUT_MS;
+ÂÂÂ data->wdt_dev.min_timeout = 1;
+ÂÂÂ data->wdt_dev.timeout = DEFAULT_TIMEOUT;
+ÂÂÂ watchdog_set_drvdata(&data->wdt_dev, data);
+
No watchdog_init_timeout() ? Any special reason for not supporting
to set the timeout with a devicetree property ?
I want to keep consistency with previous meson watchdog driver.
as follows:
- meson_gxbb_wdt.c
- meson_wdt.c


+ÂÂÂ ret = meson_sm_call(data->fw, SM_WATCHDOG_OPS, NULL,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ MESON_SIP_WDT_INIT,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ data->wdt_dev.timeout, 0, 0, 0);
+ÂÂÂ if (ret)
+ÂÂÂÂÂÂÂ return ret;
+
+ÂÂÂ watchdog_stop_on_reboot(&data->wdt_dev);
+
+ÂÂÂ return devm_watchdog_register_device(dev, &data->wdt_dev);
+}
+
+static struct platform_driver meson_sec_wdt_driver = {
+ÂÂÂ .probeÂÂÂ = meson_sec_wdt_probe,
+ÂÂÂ .driver = {
+ÂÂÂÂÂÂÂ .name = "meson-sec-wdt",
+ÂÂÂÂÂÂÂ .pm = &meson_sec_wdt_pm_ops,
+ÂÂÂÂÂÂÂ .of_match_tableÂÂÂ = meson_sec_wdt_dt_ids,
+ÂÂÂ },
+};
+
+module_platform_driver(meson_sec_wdt_driver);
+
+MODULE_AUTHOR("Xingyu Chen <xingyu.chen@xxxxxxxxxxx>");
+MODULE_DESCRIPTION("Amlogic Secure Watchdog Timer Driver");
+MODULE_LICENSE("Dual BSD/GPL");

BSD or MIT ? This should match the license identifier.
MIT, I will fix it in next verson.

.