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Date:   Sun, 26 Feb 2017 22:07:32 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, mike.leach@...aro.org
Subject: Re: [PATCH v1 2/2] coresight: add support for debug module

On Fri, Feb 24, 2017 at 12:07:11PM -0700, Mathieu Poirier wrote:
> On Thu, Feb 23, 2017 at 09:57:47AM +0800, Leo Yan wrote:

[...]

> > +/* bits definition for EDDEVID1 */
> > +#define EDDEVID1_PCSR_OFFSET_MASK	GENMASK(3, 0)
> > +#define EDDEVID1_PCSR_OFFSET_INS_SET	(0x0)
> > +#define EDDEVID1_PCSR_NO_OFFSET		(0x1)
> 
> Hi Leo,
> 
> The above #define isn't used in the code - please remove.

Thanks a lot for quite detailed reivew and suggestion for below
refactors. I will follow up them and send out new version for
reviewing.

Thanks,
Leo Yan

> > +
> > +/* bits definition for EDDEVID */
> > +#define EDDEVID_PCSAMPLE_MODE		GENMASK(3, 0)
> > +#define EDDEVID_IMPL_NONE		(0x0)
> > +#define EDDEVID_IMPL_EDPCSR_EDCIDSR	(0x2)
> > +#define EDDEVID_IMPL_FULL		(0x3)
> > +
> > +struct debug_drvdata {
> > +	void __iomem	*base;
> > +	struct device	*dev;
> > +	int		cpu;
> > +	struct clk	*dbg_clk;
> > +
> > +	bool		edpcsr_present;
> > +	bool		edvidsr_present;
> > +	bool		pc_has_offset;
> > +
> > +	u32		eddevid;
> > +	u32		eddevid1;
> > +
> > +	u32		edpcsr;
> > +	u32		edpcsr_hi;
> > +	u32		edprsr;
> > +	u32		edvidsr;
> > +	u32		edcidsr;
> > +};
> > +
> > +static int debug_count;
> 
> No need to make this global - please move this to debug_probe() 
> 
> > +static DEFINE_PER_CPU(struct debug_drvdata *, debug_drvdata);
> > +
> > +static void debug_os_unlock(struct debug_drvdata *drvdata)
> > +{
> > +	/* Unlocks the debug registers */
> > +	writel_relaxed(0x0, drvdata->base + EDOSLAR);
> > +	wmb();
> > +}
> > +
> > +/*
> > + * According to ARM DDI 0487A.k, before access external debug
> > + * registers should firstly check the access permission; if any
> > + * below condition has been met then cannot access debug
> > + * registers to avoid lockup issue:
> > + *
> > + * - CPU power domain is powered off;
> > + * - The OS Double Lock is locked;
> > + *
> > + * By checking EDPRSR can get to know if meet these conditions.
> > + */
> > +static bool debug_access_permit(struct debug_drvdata *drvdata)
> 
> s/debug_access_permit/debug_access_permitted
> 
> > +{
> > +	/* CPU is powered off */
> > +	if (!(drvdata->edprsr & EDPRSR_PU))
> > +		return false;
> > +
> > +	/* The OS Double Lock is locked */
> > +	if (drvdata->edprsr & EDPRSR_DLK)
> > +		return false;
> > +
> > +	return true;
> > +}
> > +
> > +static void debug_read_regs(struct debug_drvdata *drvdata)
> > +{
> > +	drvdata->edprsr = readl_relaxed(drvdata->base + EDPRSR);
> > +
> > +	if (!debug_access_permit(drvdata))
> > +		return;
> > +
> > +	if (!drvdata->edpcsr_present)
> > +		return;
> > +
> > +	CS_UNLOCK(drvdata->base);
> > +
> > +	debug_os_unlock(drvdata);
> > +
> > +	drvdata->edpcsr = readl_relaxed(drvdata->base + EDPCSR);
> > +
> > +	/*
> > +	 * As described in ARM DDI 0487A.k, if the processing
> > +	 * element (PE) is in debug state, or sample-based
> > +	 * profiling is prohibited, EDPCSR reads as 0xFFFFFFFF;
> > +	 * EDCIDSR, EDVIDSR and EDPCSR_HI registers also become
> > +	 * UNKNOWN state. So directly bail out for this case.
> > +	 */
> > +	if (drvdata->edpcsr == EDPCSR_PROHIBITED) {
> > +		CS_LOCK(drvdata->base);
> > +		return;
> > +	}
> > +
> > +	/*
> > +	 * A read of the EDPCSR normally has the side-effect of
> > +	 * indirectly writing to EDCIDSR, EDVIDSR and EDPCSR_HI;
> > +	 * at this point it's safe to read value from them.
> > +	 */
> > +	drvdata->edcidsr = readl_relaxed(drvdata->base + EDCIDSR);
> > +#ifdef CONFIG_64BIT
> > +	drvdata->edpcsr_hi = readl_relaxed(drvdata->base + EDPCSR_HI);
> > +#endif
> > +
> > +	if (drvdata->edvidsr_present)
> > +		drvdata->edvidsr = readl_relaxed(drvdata->base + EDVIDSR);
> > +
> > +	CS_LOCK(drvdata->base);
> > +}
> > +
> > +#ifndef CONFIG_64BIT
> > +static bool debug_pc_has_offset(struct debug_drvdata *drvdata)
> > +{
> > +	u32 pcsr_offset;
> > +
> > +	pcsr_offset = drvdata->eddevid1 & EDDEVID1_PCSR_OFFSET_MASK;
> > +
> > +	return (pcsr_offset == EDDEVID1_PCSR_OFFSET_INS_SET);
> > +}
> > +
> > +static unsigned long debug_adjust_pc(struct debug_drvdata *drvdata,
> > +				     unsigned long pc)
> > +{
> > +	unsigned long arm_inst_offset = 0, thumb_inst_offset = 0;
> > +
> > +	if (debug_pc_has_offset(drvdata)) {
> > +		arm_inst_offset = 8;
> > +		thumb_inst_offset = 4;
> > +	}
> > +
> > +	/* Handle thumb instruction */
> > +	if (pc & EDPCSR_THUMB) {
> > +		pc = (pc & EDPCSR_THUMB_INST_MASK) - thumb_inst_offset;
> > +		return pc;
> > +	}
> > +
> > +	/*
> > +	 * Handle arm instruction offset, if the arm instruction
> > +	 * is not 4 byte alignment then it's possible the case
> > +	 * for implementation defined; keep original value for this
> > +	 * case and print info for notice.
> > +	 */
> > +	if (pc & BIT(1))
> > +		pr_emerg("Instruction offset is implementation defined\n");
> > +	else
> > +		pc = (pc & EDPCSR_ARM_INST_MASK) - arm_inst_offset;
> > +
> > +	return pc;
> > +}
> > +#endif
> > +
> > +static void debug_dump_regs(struct debug_drvdata *drvdata)
> > +{
> > +	unsigned long pc;
> > +
> > +	pr_emerg("\tEDPRSR:  %08x (Power:%s DLK:%s)\n", drvdata->edprsr,
> > +		 drvdata->edprsr & EDPRSR_PU ? "On" : "Off",
> > +		 drvdata->edprsr & EDPRSR_DLK ? "Lock" : "Unlock");
> > +
> > +	if (!debug_access_permit(drvdata) || !drvdata->edpcsr_present) {
> > +		pr_emerg("No permission to access debug registers!\n");
> > +		return;
> > +	}
> > +
> > +	if (drvdata->edpcsr == EDPCSR_PROHIBITED) {
> > +		pr_emerg("CPU is in Debug state or profiling is prohibited!\n");
> > +		return;
> > +	}
> > +
> > +#ifdef CONFIG_64BIT
> > +	pc = (unsigned long)drvdata->edpcsr_hi << 32 |
> > +	     (unsigned long)drvdata->edpcsr;
> > +#else
> > +	pc = debug_adjust_pc(drvdata, (unsigned long)drvdata->edpcsr);
> > +#endif
> > +
> > +	pr_emerg("\tEDPCSR:  [<%p>] %pS\n", (void *)pc, (void *)pc);
> > +	pr_emerg("\tEDCIDSR: %08x\n", drvdata->edcidsr);
> > +
> > +	if (!drvdata->edvidsr_present)
> > +		return;
> > +
> > +	pr_emerg("\tEDVIDSR: %08x (State:%s Mode:%s Width:%s VMID:%x)\n",
> > +		 drvdata->edvidsr,
> > +		 drvdata->edvidsr & EDVIDSR_NS ? "Non-secure" : "Secure",
> > +		 drvdata->edvidsr & EDVIDSR_E3 ? "EL3" :
> > +			(drvdata->edvidsr & EDVIDSR_E2 ? "EL2" : "EL1/0"),
> > +		 drvdata->edvidsr & EDVIDSR_HV ? "64bits" : "32bits",
> > +		 drvdata->edvidsr & (u32)EDVIDSR_VMID);
> > +}
> > +
> > +/*
> > + * Dump out information on panic.
> > + */
> > +static int debug_notifier_call(struct notifier_block *self,
> > +			       unsigned long v, void *p)
> > +{
> > +	int cpu;
> > +
> > +	pr_emerg("ARM external debug module:\n");
> > +
> > +	for_each_possible_cpu(cpu) {
> > +
> > +		if (!per_cpu(debug_drvdata, cpu))
> > +			continue;
> > +
> > +		pr_emerg("CPU[%d]:\n", per_cpu(debug_drvdata, cpu)->cpu);
> > +
> > +		debug_read_regs(per_cpu(debug_drvdata, cpu));
> > +		debug_dump_regs(per_cpu(debug_drvdata, cpu));
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static struct notifier_block debug_notifier = {
> > +	.notifier_call = debug_notifier_call,
> > +};
> > +
> > +static void debug_init_arch_data(void *info)
> > +{
> > +	struct debug_drvdata *drvdata = info;
> > +	u32 mode;
> > +
> > +	CS_UNLOCK(drvdata->base);
> > +
> > +	debug_os_unlock(drvdata);
> > +
> > +	/* Read device info */
> > +	drvdata->eddevid  = readl_relaxed(drvdata->base + EDDEVID);
> > +	drvdata->eddevid1 = readl_relaxed(drvdata->base + EDDEVID1);
> > +
> > +	/* Parse implementation feature */
> > +	mode = drvdata->eddevid & EDDEVID_PCSAMPLE_MODE;
> > +	if (mode == EDDEVID_IMPL_FULL) {
> > +		drvdata->edpcsr_present  = true;
> > +		drvdata->edvidsr_present = true;
> > +	} else if (mode == EDDEVID_IMPL_EDPCSR_EDCIDSR) {
> > +		drvdata->edpcsr_present  = true;
> > +		drvdata->edvidsr_present = false;
> > +	} else {
> > +		drvdata->edpcsr_present  = false;
> > +		drvdata->edvidsr_present = false;
> > +	}
> > +
> > +	CS_LOCK(drvdata->base);
> > +}
> > +
> > +static int debug_probe(struct amba_device *adev, const struct amba_id *id)
> > +{
> > +	int ret;
> > +	void __iomem *base;
> > +	struct device *dev = &adev->dev;
> > +	struct coresight_platform_data *pdata = NULL;
> > +	struct debug_drvdata *drvdata;
> > +	struct resource *res = &adev->res;
> > +	struct device_node *np = adev->dev.of_node;
> > +
> > +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> > +	if (!drvdata)
> > +		return -ENOMEM;
> > +
> > +	if (np) {
> > +		pdata = of_get_coresight_platform_data(dev, np);
> > +		if (IS_ERR(pdata))
> > +			return PTR_ERR(pdata);
> > +		adev->dev.platform_data = pdata;
> > +	}
> 
> I wonder if dragging a coresight_platform_data is worth it.  From what I see the
> only thing it is used for is to retrieve the CPU.  As such I think it is better
> get the portion of code in of_get_coresight_platform_data() that deals with the
> CPU and create a new function (of_coresight_get_cpu()).  That way you can reuse
> it here and in of_get_coresight_platform_data(). 
> 
> > +
> > +	drvdata->dev = &adev->dev;
> > +	drvdata->dbg_clk = devm_clk_get(&adev->dev, "dbg_clk");
> > +	if (IS_ERR(drvdata->dbg_clk)) {
> > +		dev_err(dev, "debug clock initialization failed.\n");
> > +		return PTR_ERR(drvdata->dbg_clk);
> > +	}
> > +
> > +	ret = clk_prepare_enable(drvdata->dbg_clk);
> > +	if (ret)
> > +		return ret;
> > +
> > +	dev_set_drvdata(dev, drvdata);
> > +
> > +	/* Validity for the resource is already checked by the AMBA core */
> > +	base = devm_ioremap_resource(dev, res);
> > +	if (IS_ERR(base))
> > +		return PTR_ERR(base);
> > +
> > +	drvdata->base = base;
> > +	drvdata->cpu = pdata ? pdata->cpu : 0;
> > +
> > +	get_online_cpus();
> > +	per_cpu(debug_drvdata, drvdata->cpu) = drvdata;
> > +
> > +	if (smp_call_function_single(drvdata->cpu,
> > +				debug_init_arch_data, drvdata, 1))
> > +		dev_err(dev, "Debug arch init failed\n");
> > +
> > +	if (!debug_count++)
> > +		atomic_notifier_chain_register(&panic_notifier_list,
> > +					       &debug_notifier);
> > +	put_online_cpus();
> 
> There is no need to hold the CPUs in place through the chain registration.  This
> should go before the if().
> 
> > +
> > +	dev_info(dev, "%s initialized\n", (char *)id->data);
>         
>         fprintf(buffer, (char *)id->data, drvdata->cpu);
>         dev_info(dev, "%s initialized\n", buffer);
> 
> > +	return 0;
> > +}
> > +
> > +static struct amba_id debug_ids[] = {
> > +	{       /* Debug for Cortex-A53 */
> > +		.id	= 0x000bbd03,
> > +		.mask	= 0x000fffff,
> > +		.data	= "debug",
>        
>                 .data   = "Coresight debug-CPU%d",
> 
> > +	},
> > +	{       /* Debug for Cortex-A57 */
> > +		.id	= 0x000bbd07,
> > +		.mask	= 0x000fffff,
> > +		.data	= "debug",
> > +	},
> > +	{       /* Debug for Cortex-A72 */
> > +		.id	= 0x000bbd08,
> > +		.mask	= 0x000fffff,
> > +		.data	= "debug",
> > +	},
> > +	{ 0, 0},
> > +};
> > +
> > +static struct amba_driver debug_driver = {
> > +	.drv = {
> > +		.name   = "coresight-debug",
> > +		.suppress_bind_attrs = true,
> > +	},
> > +	.probe		= debug_probe,
> > +	.id_table	= debug_ids,
> > +};
> > +builtin_amba_driver(debug_driver);
> > -- 
> > 2.7.4
> > 

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