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Subject: Re: [PATCH 2/2] remoteproc: k3-r5: Extend support to R5F clusters on
 AM64x SoCs
To:     Mathieu Poirier <mathieu.poirier@linaro.org>
CC:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        Rob Herring <robh+dt@kernel.org>,
        Lokesh Vutla <lokeshvutla@ti.com>,
        <linux-remoteproc@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>,
        <linux-kernel@vger.kernel.org>
References: <20210318215842.8196-1-s-anna@ti.com>
 <20210318215842.8196-3-s-anna@ti.com> <20210325173000.GB1806983@xps15>
 <196befa6-06ee-3ac9-2fdc-cf2e1eca400e@ti.com>
 <20210325221726.GA1974659@xps15>
From:   Suman Anna <s-anna@ti.com>
Message-ID: <a200cb01-5df5-ecfc-0c27-e17a4d92298c@ti.com>
Date:   Fri, 26 Mar 2021 09:50:55 -0500
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On 3/25/21 5:17 PM, Mathieu Poirier wrote:
> On Thu, Mar 25, 2021 at 04:00:55PM -0500, Suman Anna wrote:
>> Hi Mathieu,
>>
>> On 3/25/21 12:30 PM, Mathieu Poirier wrote:
>>> Good morning,
>>>
>>> On Thu, Mar 18, 2021 at 04:58:42PM -0500, Suman Anna wrote:
>>>> The K3 AM64x SoC family has a revised R5F sub-system and contains a
>>>> subset of the R5F clusters present on J721E SoCs. The K3 AM64x SoCs
>>>> only have two dual-core Arm R5F clusters/subsystems with 2 R5F cores
>>>> each present within the MAIN voltage domain (MAIN_R5FSS0 & MAIN_R5FSS1).
>>>>
>>>> The revised IP has the following distinct features:
>>>>  1. The R5FSS IP supports a new "Single-CPU" mode instead of the LockStep
>>>>     mode on existing SoCs (AM65x, J721E or J7200). This mode is similar
>>>>     to LockStep-mode on J7200 SoCs in terms of TCM usage without the
>>>>     fault-tolerant safety feature provided by the LockStep mode.
>>>>
>>>>     The Core1 TCMs are combined with the Core0 TCMs effectively doubling
>>>>     the amount of TCMs available in Single-CPU mode. The LockStep-mode
>>>>     on previous AM65x and J721E SoCs could only use the Core0 TCMs. These
>>>>     combined TCMs appear contiguous at the respective Core0 TCM addresses.
>>>>     The code though is executed only on a single CPU (on Core0), and as
>>>>     such, requires the halt signal to be programmed only for Core0, while
>>>>     the resets need to be managed for both the cores.
>>>>
>>>>  2. TCMs are auto-initialized during module power-up, and the behavior
>>>>     is programmable through a MMR bit. This feature is the same as on
>>>>     the recent J7200 SoCs.
>>>>
>>>> Extend the support to these clusters in the K3 R5F remoteproc driver
>>>> using AM64x specific compatibles. New TI-SCI flags and a unique cluster
>>>> mode are also needed for the cluster mode detection on these SoCs. The
>>>> reset assert and deassert sequence of both the cores in Single-CPU mode
>>>> is agnostic of the order, so the same LockStep reset and release sequences
>>>> are re-used.
>>>>
>>>> The integration of these clusters is very much similar to existing SoCs
>>>> otherwise.
>>>>
>>>> Signed-off-by: Suman Anna <s-anna@ti.com>
>>>> ---
>>>>  drivers/remoteproc/ti_k3_r5_remoteproc.c | 155 ++++++++++++++++++-----
>>>>  1 file changed, 126 insertions(+), 29 deletions(-)
>>>>
>>>> diff --git a/drivers/remoteproc/ti_k3_r5_remoteproc.c b/drivers/remoteproc/ti_k3_r5_remoteproc.c
>>>> index 5cf8d030a1f0..497f0d05b887 100644
>>>> --- a/drivers/remoteproc/ti_k3_r5_remoteproc.c
>>>> +++ b/drivers/remoteproc/ti_k3_r5_remoteproc.c
>>>> @@ -40,6 +40,8 @@
>>>>  #define PROC_BOOT_CFG_FLAG_R5_ATCM_EN			0x00002000
>>>>  /* Available from J7200 SoCs onwards */
>>>>  #define PROC_BOOT_CFG_FLAG_R5_MEM_INIT_DIS		0x00004000
>>>> +/* Applicable to only AM64x SoCs */
>>>> +#define PROC_BOOT_CFG_FLAG_R5_SINGLE_CORE		0x00008000
>>>>  
>>>>  /* R5 TI-SCI Processor Control Flags */
>>>>  #define PROC_BOOT_CTRL_FLAG_R5_CORE_HALT		0x00000001
>>>> @@ -49,6 +51,8 @@
>>>>  #define PROC_BOOT_STATUS_FLAG_R5_WFI			0x00000002
>>>>  #define PROC_BOOT_STATUS_FLAG_R5_CLK_GATED		0x00000004
>>>>  #define PROC_BOOT_STATUS_FLAG_R5_LOCKSTEP_PERMITTED	0x00000100
>>>> +/* Applicable to only AM64x SoCs */
>>>> +#define PROC_BOOT_STATUS_FLAG_R5_SINGLECORE_ONLY	0x00000200
>>>>  
>>>>  /**
>>>>   * struct k3_r5_mem - internal memory structure
>>>> @@ -64,19 +68,29 @@ struct k3_r5_mem {
>>>>  	size_t size;
>>>>  };
>>>>  
>>>> +/*
>>>> + * All cluster mode values are not applicable on all SoCs. The following
>>>> + * are the modes supported on various SoCs:
>>>> + *   Split mode      : AM65x, J721E, J7200 and AM64x SoCs
>>>> + *   LockStep mode   : AM65x, J721E and J7200 SoCs
>>>> + *   Single-CPU mode : AM64x SoCs only
>>>> + */
>>>>  enum cluster_mode {
>>>>  	CLUSTER_MODE_SPLIT = 0,
>>>>  	CLUSTER_MODE_LOCKSTEP,
>>>> +	CLUSTER_MODE_SINGLECPU,
>>>>  };
>>>>  
>>>>  /**
>>>>   * struct k3_r5_soc_data - match data to handle SoC variations
>>>>   * @tcm_is_double: flag to denote the larger unified TCMs in certain modes
>>>>   * @tcm_ecc_autoinit: flag to denote the auto-initialization of TCMs for ECC
>>>> + * @single_cpu_mode: flag to denote if SoC/IP supports Single-CPU mode
>>>>   */
>>>>  struct k3_r5_soc_data {
>>>>  	bool tcm_is_double;
>>>>  	bool tcm_ecc_autoinit;
>>>> +	bool single_cpu_mode;
>>>>  };
>>>>  
>>>>  /**
>>>> @@ -369,6 +383,13 @@ static inline int k3_r5_core_run(struct k3_r5_core *core)
>>>>   * applicable cores to allow loading into the TCMs. The .prepare() ops is
>>>>   * invoked by remoteproc core before any firmware loading, and is followed
>>>>   * by the .start() ops after loading to actually let the R5 cores run.
>>>> + *
>>>> + * The Single-CPU mode on applicable SoCs (eg: AM64x) only uses Core0 to
>>>> + * execute code, but combines the TCMs from both cores. The resets for both
>>>> + * cores need to be released to make this possible, as the TCMs are in general
>>>> + * private to each core. Only Core0 needs to be unhalted for running the
>>>> + * cluster in this mode. The function uses the same reset logic as LockStep
>>>> + * mode for this (though the behavior is agnostic of the reset release order).
>>>>   */
>>>>  static int k3_r5_rproc_prepare(struct rproc *rproc)
>>>>  {
>>>> @@ -386,7 +407,9 @@ static int k3_r5_rproc_prepare(struct rproc *rproc)
>>>>  		return ret;
>>>>  	mem_init_dis = !!(cfg & PROC_BOOT_CFG_FLAG_R5_MEM_INIT_DIS);
>>>>  
>>>> -	ret = (cluster->mode == CLUSTER_MODE_LOCKSTEP) ?
>>>> +	/* Re-use LockStep-mode reset logic for Single-CPU mode */
>>>> +	ret = (cluster->mode == CLUSTER_MODE_LOCKSTEP ||
>>>> +	       cluster->mode == CLUSTER_MODE_SINGLECPU) ?
>>>>  		k3_r5_lockstep_release(cluster) : k3_r5_split_release(core);
>>>>  	if (ret) {
>>>>  		dev_err(dev, "unable to enable cores for TCM loading, ret = %d\n",
>>>> @@ -427,6 +450,12 @@ static int k3_r5_rproc_prepare(struct rproc *rproc)
>>>>   * cores. The cores themselves are only halted in the .stop() ops, and the
>>>>   * .unprepare() ops is invoked by the remoteproc core after the remoteproc is
>>>>   * stopped.
>>>> + *
>>>> + * The Single-CPU mode on applicable SoCs (eg: AM64x) combines the TCMs from
>>>> + * both cores. The access is made possible only with releasing the resets for
>>>> + * both cores, but with only Core0 unhalted. This function re-uses the same
>>>> + * reset assert logic as LockStep mode for this mode (though the behavior is
>>>> + * agnostic of the reset assert order).
>>>>   */
>>>>  static int k3_r5_rproc_unprepare(struct rproc *rproc)
>>>>  {
>>>> @@ -436,7 +465,9 @@ static int k3_r5_rproc_unprepare(struct rproc *rproc)
>>>>  	struct device *dev = kproc->dev;
>>>>  	int ret;
>>>>  
>>>> -	ret = (cluster->mode == CLUSTER_MODE_LOCKSTEP) ?
>>>> +	/* Re-use LockStep-mode reset logic for Single-CPU mode */
>>>> +	ret = (cluster->mode == CLUSTER_MODE_LOCKSTEP ||
>>>> +	       cluster->mode == CLUSTER_MODE_SINGLECPU) ?
>>>>  		k3_r5_lockstep_reset(cluster) : k3_r5_split_reset(core);
>>>>  	if (ret)
>>>>  		dev_err(dev, "unable to disable cores, ret = %d\n", ret);
>>>> @@ -455,6 +486,10 @@ static int k3_r5_rproc_unprepare(struct rproc *rproc)
>>>>   * first followed by Core0. The Split-mode requires that Core0 to be maintained
>>>>   * always in a higher power state that Core1 (implying Core1 needs to be started
>>>>   * always only after Core0 is started).
>>>> + *
>>>> + * The Single-CPU mode on applicable SoCs (eg: AM64x) only uses Core0 to execute
>>>> + * code, so only Core0 needs to be unhalted. The function uses the same logic
>>>> + * flow as Split-mode for this.
>>>>   */
>>>>  static int k3_r5_rproc_start(struct rproc *rproc)
>>>>  {
>>>> @@ -539,6 +574,10 @@ static int k3_r5_rproc_start(struct rproc *rproc)
>>>>   * Core0 to be maintained always in a higher power state that Core1 (implying
>>>>   * Core1 needs to be stopped first before Core0).
>>>>   *
>>>> + * The Single-CPU mode on applicable SoCs (eg: AM64x) only uses Core0 to execute
>>>> + * code, so only Core0 needs to be halted. The function uses the same logic
>>>> + * flow as Split-mode for this.
>>>> + *
>>>>   * Note that the R5F halt operation in general is not effective when the R5F
>>>>   * core is running, but is needed to make sure the core won't run after
>>>>   * deasserting the reset the subsequent time. The asserting of reset can
>>>> @@ -665,7 +704,9 @@ static const struct rproc_ops k3_r5_rproc_ops = {
>>>>   *
>>>>   * Each R5FSS has a cluster-level setting for configuring the processor
>>>>   * subsystem either in a safety/fault-tolerant LockStep mode or a performance
>>>> - * oriented Split mode. Each R5F core has a number of settings to either
>>>> + * oriented Split mode on most SoCs. A fewer SoCs support a non-safety mode
>>>> + * as an alternate for LockStep mode that exercises only a single R5F core
>>>> + * called Single-CPU mode. Each R5F core has a number of settings to either
>>>>   * enable/disable each of the TCMs, control which TCM appears at the R5F core's
>>>>   * address 0x0. These settings need to be configured before the resets for the
>>>>   * corresponding core are released. These settings are all protected and managed
>>>> @@ -677,11 +718,13 @@ static const struct rproc_ops k3_r5_rproc_ops = {
>>>>   * the cores are halted before the .prepare() step.
>>>>   *
>>>>   * The function is called from k3_r5_cluster_rproc_init() and is invoked either
>>>> - * once (in LockStep mode) or twice (in Split mode). Support for LockStep-mode
>>>> - * is dictated by an eFUSE register bit, and the config settings retrieved from
>>>> - * DT are adjusted accordingly as per the permitted cluster mode. All cluster
>>>> - * level settings like Cluster mode and TEINIT (exception handling state
>>>> - * dictating ARM or Thumb mode) can only be set and retrieved using Core0.
>>>> + * once (in LockStep mode or Single-CPU modes) or twice (in Split mode). Support
>>>> + * for LockStep-mode is dictated by an eFUSE register bit, and the config
>>>> + * settings retrieved from DT are adjusted accordingly as per the permitted
>>>> + * cluster mode. Another eFUSE register bit dictates if the R5F cluster only
>>>> + * supports a Single-CPU mode. All cluster level settings like Cluster mode and
>>>> + * TEINIT (exception handling state dictating ARM or Thumb mode) can only be set
>>>> + * and retrieved using Core0.
>>>>   *
>>>>   * The function behavior is different based on the cluster mode. The R5F cores
>>>>   * are configured independently as per their individual settings in Split mode.
>>>> @@ -700,10 +743,16 @@ static int k3_r5_rproc_configure(struct k3_r5_rproc *kproc)
>>>>  	u32 set_cfg = 0, clr_cfg = 0;
>>>>  	u64 boot_vec = 0;
>>>>  	bool lockstep_en;
>>>> +	bool single_cpu;
>>>>  	int ret;
>>>>  
>>>>  	core0 = list_first_entry(&cluster->cores, struct k3_r5_core, elem);
>>>> -	core = (cluster->mode == CLUSTER_MODE_LOCKSTEP) ? core0 : kproc->core;
>>>> +	if (cluster->mode == CLUSTER_MODE_LOCKSTEP ||
>>>> +	    cluster->mode == CLUSTER_MODE_SINGLECPU) {
>>>> +		core = core0;
>>>> +	} else {
>>>> +		core = kproc->core;
>>>> +	}
>>>>  
>>>>  	ret = ti_sci_proc_get_status(core->tsp, &boot_vec, &cfg, &ctrl,
>>>>  				     &stat);
>>>> @@ -713,23 +762,48 @@ static int k3_r5_rproc_configure(struct k3_r5_rproc *kproc)
>>>>  	dev_dbg(dev, "boot_vector = 0x%llx, cfg = 0x%x ctrl = 0x%x stat = 0x%x\n",
>>>>  		boot_vec, cfg, ctrl, stat);
>>>>  
>>>> +	/* check if only Single-CPU mode is supported on applicable SoCs */
>>>> +	if (cluster->soc_data->single_cpu_mode) {
>>>> +		single_cpu =
>>>> +			!!(stat & PROC_BOOT_STATUS_FLAG_R5_SINGLECORE_ONLY);
>>>> +		if (single_cpu && cluster->mode == CLUSTER_MODE_SPLIT) {
>>>> +			dev_err(cluster->dev, "split-mode not permitted, force configuring for single-cpu mode\n");
>>>> +			cluster->mode = CLUSTER_MODE_SINGLECPU;
>>>> +		}
>>>> +		goto config;
>>>> +	}
>>>> +
>>>> +	/* check conventional LockStep vs Split mode configuration */
>>>>  	lockstep_en = !!(stat & PROC_BOOT_STATUS_FLAG_R5_LOCKSTEP_PERMITTED);
>>>>  	if (!lockstep_en && cluster->mode == CLUSTER_MODE_LOCKSTEP) {
>>>>  		dev_err(cluster->dev, "lockstep mode not permitted, force configuring for split-mode\n");
>>>>  		cluster->mode = CLUSTER_MODE_SPLIT;
>>>>  	}
>>>>  
>>>> +config:
>>>>  	/* always enable ARM mode and set boot vector to 0 */
>>>>  	boot_vec = 0x0;
>>>>  	if (core == core0) {
>>>>  		clr_cfg = PROC_BOOT_CFG_FLAG_R5_TEINIT;
>>>> -		/*
>>>> -		 * LockStep configuration bit is Read-only on Split-mode _only_
>>>> -		 * devices and system firmware will NACK any requests with the
>>>> -		 * bit configured, so program it only on permitted devices
>>>> -		 */
>>>> -		if (lockstep_en)
>>>> -			clr_cfg |= PROC_BOOT_CFG_FLAG_R5_LOCKSTEP;
>>>> +		if (cluster->soc_data->single_cpu_mode) {
>>>> +			/*
>>>> +			 * Single-CPU configuration bit can only be configured
>>>> +			 * on Core0 and system firmware will NACK any requests
>>>> +			 * with the bit configured, so program it only on
>>>> +			 * permitted cores
>>>> +			 */
>>>> +			if (cluster->mode == CLUSTER_MODE_SINGLECPU)
>>>> +				set_cfg = PROC_BOOT_CFG_FLAG_R5_SINGLE_CORE;
>>>> +		} else {
>>>> +			/*
>>>> +			 * LockStep configuration bit is Read-only on Split-mode
>>>> +			 * _only_ devices and system firmware will NACK any
>>>> +			 * requests with the bit configured, so program it only
>>>> +			 * on permitted devices
>>>> +			 */
>>>> +			if (lockstep_en)
>>>> +				clr_cfg |= PROC_BOOT_CFG_FLAG_R5_LOCKSTEP;
>>>> +		}
>>>>  	}
>>>>  
>>>>  	if (core->atcm_enable)
>>>> @@ -894,12 +968,12 @@ static void k3_r5_reserved_mem_exit(struct k3_r5_rproc *kproc)
>>>>   * cores are usable in Split-mode, but only the Core0 TCMs can be used in
>>>>   * LockStep-mode. The newer revisions of the R5FSS IP maximizes these TCMs by
>>>>   * leveraging the Core1 TCMs as well in certain modes where they would have
>>>> - * otherwise been unusable (Eg: LockStep-mode on J7200 SoCs). This is done by
>>>> - * making a Core1 TCM visible immediately after the corresponding Core0 TCM.
>>>> - * The SoC memory map uses the larger 64 KB sizes for the Core0 TCMs, and the
>>>> - * dts representation reflects this increased size on supported SoCs. The Core0
>>>> - * TCM sizes therefore have to be adjusted to only half the original size in
>>>> - * Split mode.
>>>> + * otherwise been unusable (Eg: LockStep-mode on J7200 SoCs, Single-CPU mode on
>>>> + * AM64x SoCs). This is done by making a Core1 TCM visible immediately after the
>>>> + * corresponding Core0 TCM. The SoC memory map uses the larger 64 KB sizes for
>>>> + * the Core0 TCMs, and the dts representation reflects this increased size on
>>>> + * supported SoCs. The Core0 TCM sizes therefore have to be adjusted to only
>>>> + * half the original size in Split mode.
>>>>   */
>>>>  static void k3_r5_adjust_tcm_sizes(struct k3_r5_rproc *kproc)
>>>>  {
>>>> @@ -909,6 +983,7 @@ static void k3_r5_adjust_tcm_sizes(struct k3_r5_rproc *kproc)
>>>>  	struct k3_r5_core *core0;
>>>>  
>>>>  	if (cluster->mode == CLUSTER_MODE_LOCKSTEP ||
>>>> +	    cluster->mode == CLUSTER_MODE_SINGLECPU ||
>>>>  	    !cluster->soc_data->tcm_is_double)
>>>>  		return;
>>>>  
>>>> @@ -987,8 +1062,9 @@ static int k3_r5_cluster_rproc_init(struct platform_device *pdev)
>>>>  			goto err_add;
>>>>  		}
>>>>  
>>>> -		/* create only one rproc in lockstep mode */
>>>> -		if (cluster->mode == CLUSTER_MODE_LOCKSTEP)
>>>> +		/* create only one rproc in lockstep mode or single-cpu mode */
>>>> +		if (cluster->mode == CLUSTER_MODE_LOCKSTEP ||
>>>> +		    cluster->mode == CLUSTER_MODE_SINGLECPU)
>>>>  			break;
>>>>  	}
>>>>  
>>>> @@ -1020,11 +1096,12 @@ static void k3_r5_cluster_rproc_exit(void *data)
>>>>  	struct rproc *rproc;
>>>>  
>>>>  	/*
>>>> -	 * lockstep mode has only one rproc associated with first core, whereas
>>>> -	 * split-mode has two rprocs associated with each core, and requires
>>>> -	 * that core1 be powered down first
>>>> +	 * lockstep mode and single-cpu modes have only one rproc associated
>>>> +	 * with first core, whereas split-mode has two rprocs associated with
>>>> +	 * each core, and requires that core1 be powered down first
>>>>  	 */
>>>> -	core = (cluster->mode == CLUSTER_MODE_LOCKSTEP) ?
>>>> +	core = (cluster->mode == CLUSTER_MODE_LOCKSTEP ||
>>>> +		cluster->mode == CLUSTER_MODE_SINGLECPU) ?
>>>>  		list_first_entry(&cluster->cores, struct k3_r5_core, elem) :
>>>>  		list_last_entry(&cluster->cores, struct k3_r5_core, elem);
>>>>  
>>>> @@ -1396,7 +1473,12 @@ static int k3_r5_probe(struct platform_device *pdev)
>>>>  		return -ENOMEM;
>>>>  
>>>>  	cluster->dev = dev;
>>>> -	cluster->mode = CLUSTER_MODE_LOCKSTEP;
>>>> +	/*
>>>> +	 * default to most common efuse configurations - Split-mode on AM64x
>>>> +	 * and LockStep-mode on all others
>>>> +	 */
>>>> +	cluster->mode = data->single_cpu_mode ?
>>>> +				CLUSTER_MODE_SPLIT : CLUSTER_MODE_LOCKSTEP;
>>>
>>> I had another look after reading your comment yesterday and I
>>> still think this patch is introducing two variables to keep track of a single
>>> state.
>>
>> Hmm, did you miss the usage/logic of this variable in k3_r5_rproc_configure()?
> 
> Yes, I have considered that part carefully.  Identifying a AM64 could be done
> the same way as I suggested in the code snipped by comparing cluster->data with
> am64_soc_data.  Or simply put that comparison in a function like
> is_soc_am64(cluster) and use it in both k3_r5_probe() and
> k3_r5_rproc_configure().
> 
>> So, if I understood you correctly, you are saying cluster->mode is enough. The
>> single_cpu_mode is an SoC/IP feature, but the capability is also dictated by an
>> eFuse bit. If The eFuse bit is set, then the cluster won't even support
>> Split-mode and would only ever support Single-CPU mode.
>>
>> The eFuse bits to check between Single-CPU and LockStep capabilities vary with
>> our centralized System Firmware, so I still need to know a means of identifying
>> the SoC family to determine which flags to check, and override any configured
>> cluster mode property. Example, a Split-mode value on AM64x devices with eFuse
>> bit set is overridden to Single-CPU mode. We have similar logic on the other
>> SoCs with LockStep-mode (eFuse bit dictates whether the devices are Split-mode
>> only in those cases). So, I still need a SoC capability. I won't be able to make
>> that determination with cluster->mode variable alone.
> 
> I understand that we need to identify an SoC capability but I think we already
> have all that is required for that, we just need to use it.
> 
>>
>>>
>>> In the above hunk we want to set a default value.
>> Correct, based on the SoC families. I could use either of_device_is_compatible()
>> or a SoC match data variable.
>>
>> I suggested
>>> of_device_is_compatible() but you could also compare @data with @am64_soc_data.
>>> If the values are equal then we have an AM64 platform.
>>
>> If we want to drop single_cpu_mode, then I actually don't need to introduce
>> am64_soc_data either, but that won't allow us to differentiate J7200 vs AM64
>> (different mode capabilities). And duplicating the same values for the purpose
>> of different pointer values makes it less reader friendly IMHO.
>>
> 
> We are both using a flag to deal with this problem - what is different is the
> flag we are using.  You have a variable within am64_soc_data and I am using
> am64_soc_data itself.  The end result is the same.
> 
> To me it would not be a problem to introduce am64_soc_data for the sole purpose
> of differentiation...  But for you it is and I respect that.
> 
>>>
>>>
>>>>  	cluster->soc_data = data;
>>>>  	INIT_LIST_HEAD(&cluster->cores);
>>>>  
>>>> @@ -1406,6 +1488,12 @@ static int k3_r5_probe(struct platform_device *pdev)
>>>>  			ret);
>>>>  		return ret;
>>>>  	}
>>>> +	/*
>>>> +	 * Translate SoC-specific dts value of 1 or 2 into appropriate
>>>> +	 * driver-specific mode. Valid values are dictated by YAML binding
>>>> +	 */
>>>> +	if (cluster->mode && data->single_cpu_mode)
>>>> +		cluster->mode = CLUSTER_MODE_SINGLECPU;
>>>
>>> And here I don't see why we have to set cluster->mode again.  The default was
>>> set before calling of_property_read_u32().  To me the above two hunks could be
>>> replace with something like:
>>
>> I have added this hunk only to catch a misconfiguration case if someone had used
>> a value of 1 in AM64x dts nodes by mistake and have not validated using the
>> binding schema with dtbs_check. I could actually drop this hunk altogether if it
>> is expected that people will always add values as per schema. I have already
>> added the valid enum values for cluster modes based on compatible in the binding
>> patch.
>>
> 
> Right, I would drop this hunk.  
> 
>>>
>>>         u32 mode = UINT_MAX;
>>>
>>>         ret = of_property_read_u32(np, "ti,cluster-mode", &mode);
>>>         if (ret < 0 && ret != -EINVAL) {
>>>                 dev_err(dev, "invalid format for ti,cluster-mode, ret = %d\n",
>>>                         ret); 
>>>                 return ret;
>>>         }
>>>
>>>         /* No mode specificied in the DT, use default */
>>>         if (mode == UINT_MAX) {
>>>                 if (cluster->soc_data == &am64_soc_data)
>>>                         cluster->mode = CLUSTER_MODE_SPLIT;
>>>                 else
>>>                         cluster->mode = CLUSTER_MODE_LOCKSTEP;
>>>
>>>         } else {
>>>                 /* A mode was specified in the DT */
>>>                 if (mode > CLUSTER_MODE_SINGLECPU)
>>>                         return -EINVAL;
>>>
>>>                 cluster->mode = mode;
>>>         }
>>
>> Hmm, this looks lot more lines than the current default assignment line change.
>>
>>>
>>> If that doesn't work then I'm missing something very subtle.
>>
>> Please see my explanation above. Hopefully, it explains the subtlety :)
>>
>> Thank you for the review and suggestions.
> 
> In the end this patch works.  It is also in a platform driver, which adds
> more wiggle room for implementation choices.  As such I won't press the case
> further - we can go with this implementation, minus the extra hunk we agree to
> remove.

The logic you suggested works, but we already have the .tcm_is_double and
.tcm_ecc_autoinit flags which are also SoC capability flags, and this follows
the same style. So, thank you for agreeing to keep the current code.

v2 coming soon dropping the hunk.

regards
Suman

> 
>>
>> regards
>> Suman
>>
>>>
>>> Thanks,
>>> Mathieu
>>>
>>>>  
>>>>  	num_cores = of_get_available_child_count(np);
>>>>  	if (num_cores != 2) {
>>>> @@ -1450,17 +1538,26 @@ static int k3_r5_probe(struct platform_device *pdev)
>>>>  static const struct k3_r5_soc_data am65_j721e_soc_data = {
>>>>  	.tcm_is_double = false,
>>>>  	.tcm_ecc_autoinit = false,
>>>> +	.single_cpu_mode = false,
>>>>  };
>>>>  
>>>>  static const struct k3_r5_soc_data j7200_soc_data = {
>>>>  	.tcm_is_double = true,
>>>>  	.tcm_ecc_autoinit = true,
>>>> +	.single_cpu_mode = false,
>>>> +};
>>>> +
>>>> +static const struct k3_r5_soc_data am64_soc_data = {
>>>> +	.tcm_is_double = true,
>>>> +	.tcm_ecc_autoinit = true,
>>>> +	.single_cpu_mode = true,
>>>>  };
>>>>  
>>>>  static const struct of_device_id k3_r5_of_match[] = {
>>>>  	{ .compatible = "ti,am654-r5fss", .data = &am65_j721e_soc_data, },
>>>>  	{ .compatible = "ti,j721e-r5fss", .data = &am65_j721e_soc_data, },
>>>>  	{ .compatible = "ti,j7200-r5fss", .data = &j7200_soc_data, },
>>>> +	{ .compatible = "ti,am64-r5fss",  .data = &am64_soc_data, },
>>>>  	{ /* sentinel */ },
>>>>  };
>>>>  MODULE_DEVICE_TABLE(of, k3_r5_of_match);
>>>> -- 
>>>> 2.30.1
>>>>
>>