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Date:   Mon, 14 Mar 2022 17:24:18 -0500
From:   Bjorn Andersson <bjorn.andersson@linaro.org>
To:     Alexandre Bailon <abailon@baylibre.com>
Cc:     ohad@wizery.com, mathieu.poirier@linaro.org, robh+dt@kernel.or,
        matthias.bgg@gmail.com, linux-remoteproc@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
        stephane.leprovost@mediatek.com, khilman@baylibre.com
Subject: Re: [PATCH v4 4/7] remoteproc: mtk_apu: Add support of JTAG
Message-ID: <Yi/AkpIPO94E1qFg@builder.lan>
References: <20220304161514.994128-1-abailon@baylibre.com>
 <20220304161514.994128-5-abailon@baylibre.com>
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In-Reply-To: <20220304161514.994128-5-abailon@baylibre.com>
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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
>