Re: [PATCH v4 4/7] remoteproc: mtk_apu: Add support of JTAG

Bjorn Andersson
2022-03-14T22:24:27Z

On Fri 04 Mar 10:15 CST 2022, Alexandre Bailon wrote:

> The DSP could be debugged using JTAG.
> The support of JTAG could enabled at build time and it could be enabled
> using debugfs.
>
> Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
> ---
> drivers/remoteproc/Kconfig | 9 +++
> drivers/remoteproc/mtk_apu.c | 147 ++++++++++++++++++++++++++++++++++-
> 2 files changed, 155 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/remoteproc/Kconfig b/drivers/remoteproc/Kconfig
> index 959d24e9492c..28140cf04d8a 100644
> --- a/drivers/remoteproc/Kconfig
> +++ b/drivers/remoteproc/Kconfig
> @@ -74,6 +74,15 @@ config MTK_APU
>
> It's safe to say N here.
>
> +config MTK_APU_JTAG
> + bool "Enable support of JTAG"
> + depends on MTK_APU
> + help
> + Say y to enable support of JTAG.
> + By default, JTAG will remain disabled until it is enabled using
> + debugfs: remoteproc/remoteproc0/jtag. Write 1 to enable it and
> + 0 to disable it.
> +
> config OMAP_REMOTEPROC
> tristate "OMAP remoteproc support"
> depends on ARCH_OMAP4 || SOC_OMAP5 || SOC_DRA7XX
> diff --git a/drivers/remoteproc/mtk_apu.c b/drivers/remoteproc/mtk_apu.c
> index 867b4682b507..3905eb5b7174 100644
> --- a/drivers/remoteproc/mtk_apu.c
> +++ b/drivers/remoteproc/mtk_apu.c
> @@ -5,12 +5,14 @@
>
> #include <linux/bitops.h>
> #include <linux/clk.h>
> +#include <linux/debugfs.h>
> #include <linux/delay.h>
> #include <linux/interrupt.h>
> #include <linux/iommu.h>
> #include <linux/irq.h>
> #include <linux/module.h>
> #include <linux/of_reserved_mem.h>
> +#include <linux/pinctrl/consumer.h>
> #include <linux/platform_device.h>
> #include <linux/remoteproc.h>
> #include <linux/string.h>
> @@ -45,6 +47,11 @@
> #define CORE_DEFAULT1 (0x00000140)
> #define CORE_DEFAULT0_ARUSER_IDMA_USE_IOMMU (0x10 << 0)
> #define CORE_DEFAULT0_AWUSER_IDMA_USE_IOMMU (0x10 << 5)
> +#define CORE_DEFAULT2 (0x00000144)
> +#define CORE_DEFAULT2_DBG_EN BIT(3)
> +#define CORE_DEFAULT2_NIDEN BIT(2)
> +#define CORE_DEFAULT2_SPNIDEN BIT(1)
> +#define CORE_DEFAULT2_SPIDEN BIT(0)
> #define CORE_XTENSA_ALTRESETVEC (0x000001F8)
>
> #define VDEV_MEM_COUNT (3)
> @@ -59,6 +66,13 @@ struct mtk_apu_rproc {
> struct clk_bulk_data *clks;
> struct iommu_domain *domain;
> struct list_head mappings;
> +
> +#ifdef CONFIG_MTK_APU_JTAG
> + struct pinctrl *pinctrl;
> + struct pinctrl_state *pinctrl_jtag;
> + bool jtag_enabled;
> + struct mutex jtag_mutex;
> +#endif
> };
>
> static const char * const mt8183_clk_names[] = {
> @@ -355,6 +369,133 @@ static irqreturn_t mtk_apu_rproc_callback(int irq, void *data)
> return IRQ_WAKE_THREAD;
> }
>
> +#ifdef CONFIG_MTK_APU_JTAG

Is there a strong reason to keep this compiled out? It's not that much
code and it means that I have to build test both variations...

> +
> +static int apu_enable_jtag(struct mtk_apu_rproc *apu_rproc)
> +{
> + int ret = 0;
> +
> + mutex_lock(&apu_rproc->jtag_mutex);

What happens if you perform the below writel() when jtag is already
enabled? I.e. do you need this mutex or could you simply have
enable/disable just write the register?

> + if (apu_rproc->jtag_enabled)
> + goto err_mutex_unlock;
> +
> + writel(CORE_DEFAULT2_SPNIDEN | CORE_DEFAULT2_SPIDEN |
> + CORE_DEFAULT2_NIDEN | CORE_DEFAULT2_DBG_EN,
> + apu_rproc->base + CORE_DEFAULT2);
> +
> + apu_rproc->jtag_enabled = 1;
> +
> +err_mutex_unlock:
> + mutex_unlock(&apu_rproc->jtag_mutex);
> +
> + return ret;
> +}
> +
> +static int apu_disable_jtag(struct mtk_apu_rproc *apu_rproc)
> +{
> + int ret = 0;
> +
> + mutex_lock(&apu_rproc->jtag_mutex);
> + if (!apu_rproc->jtag_enabled)
> + goto err_mutex_unlock;
> +
> + writel(0, apu_rproc->base + CORE_DEFAULT2);
> +
> + apu_rproc->jtag_enabled = 0;
> +
> +err_mutex_unlock:
> + mutex_unlock(&apu_rproc->jtag_mutex);
> +
> + return ret;
> +}
> +
> +static ssize_t rproc_jtag_read(struct file *filp, char __user *userbuf,
> + size_t count, loff_t *ppos)
> +{
> + struct rproc *rproc = filp->private_data;
> + struct mtk_apu_rproc *apu_rproc = (struct mtk_apu_rproc *)rproc->priv;
> + char *buf = apu_rproc->jtag_enabled ? "enabled\n" : "disabled\n";
> +
> + return simple_read_from_buffer(userbuf, count, ppos, buf, strlen(buf));

Per my ask about write below, please make this read 'Y' or 'N'.

> +}
> +
> +static ssize_t rproc_jtag_write(struct file *filp, const char __user *user_buf,
> + size_t count, loff_t *ppos)
> +{
> + struct rproc *rproc = filp->private_data;
> + struct mtk_apu_rproc *apu_rproc = (struct mtk_apu_rproc *)rproc->priv;
> + char buf[10];
> + int ret;
> +
> + if (count < 1 || count > sizeof(buf))
> + return -EINVAL;
> +
> + ret = copy_from_user(buf, user_buf, count);
> + if (ret)
> + return -EFAULT;
> +
> + /* remove end of line */
> + if (buf[count - 1] == '\n')
> + buf[count - 1] = '\0';
> +

Please use kstrtobool_from_user().

> + if (!strncmp(buf, "enabled", count))
> + ret = apu_enable_jtag(apu_rproc);
> + else if (!strncmp(buf, "disabled", count))
> + ret = apu_disable_jtag(apu_rproc);
> + else
> + return -EINVAL;
> +
> + return ret ? ret : count;
> +}
> +
> +static const struct file_operations rproc_jtag_ops = {
> + .read = rproc_jtag_read,
> + .write = rproc_jtag_write,
> + .open = simple_open,
> +};
> +
> +static int apu_jtag_probe(struct mtk_apu_rproc *apu_rproc)
> +{
> + int ret;
> +
> + if (!apu_rproc->rproc->dbg_dir)
> + return -ENODEV;
> +
> + apu_rproc->pinctrl = devm_pinctrl_get(apu_rproc->dev);
> + if (IS_ERR(apu_rproc->pinctrl)) {
> + dev_warn(apu_rproc->dev, "Failed to find JTAG pinctrl\n");

I believe you failed to find the pinctrl instance for the remoteproc
driver, not for the JTAG.

> + return PTR_ERR(apu_rproc->pinctrl);
> + }
> +
> + apu_rproc->pinctrl_jtag = pinctrl_lookup_state(apu_rproc->pinctrl,
> + "jtag");
> + if (IS_ERR(apu_rproc->pinctrl_jtag))
> + return PTR_ERR(apu_rproc->pinctrl_jtag);
> +
> + ret = pinctrl_select_state(apu_rproc->pinctrl,
> + apu_rproc->pinctrl_jtag);

So if the kernel is compiled with MTK_APU_JTAG "jtag" is the new
"default" for this device?

Regards,
Bjorn

> + if (ret < 0)
> + return ret;
> +
> + mutex_init(&apu_rproc->jtag_mutex);
> +
> + debugfs_create_file("jtag", 0600, apu_rproc->rproc->dbg_dir,
> + apu_rproc->rproc, &rproc_jtag_ops);
> +
> + return 0;
> +}
> +#else
> +static int apu_jtag_probe(struct mtk_apu_rproc *apu_rproc)
> +{
> + return 0;
> +}
> +
> +static int apu_disable_jtag(struct mtk_apu_rproc *apu_rproc)
> +{
> + return 0;
> +}
> +#endif /* CONFIG_MTK_APU_JTAG */
> +
> static int mtk_apu_rproc_probe(struct platform_device *pdev)
> {
> struct device *dev = &pdev->dev;
> @@ -442,6 +583,10 @@ static int mtk_apu_rproc_probe(struct platform_device *pdev)
> goto free_rproc;
> }
>
> + ret = apu_jtag_probe(apu_rproc);
> + if (ret)
> + dev_warn(dev, "Failed to configure jtag\n");

If devm_pinctrl_get() failed you'll get two warnings, and if the user
haven't added a "jtag" pinctrl state this warning isn't very
descriptive. Consider omitting it and add appropriate error messages in
apu_jtag_probe().

Regards,
Bjorn

> +
> return 0;
>
> free_rproc:
> @@ -457,7 +602,7 @@ static int mtk_apu_rproc_remove(struct platform_device *pdev)
> struct device *dev = &pdev->dev;
>
> disable_irq(apu_rproc->irq);
> -
> + apu_disable_jtag(apu_rproc);
> rproc_del(rproc);
> of_reserved_mem_device_release(dev);
> rproc_free(rproc);
> --
> 2.34.1
>