[PATCH v4 4/5] arm: mach-k3: j721e-init.c: Add support for CONFIG_K3_OPP_LOW

[Aniket Limaye]

Hi Manorit,

On 19/11/24 11:42, Manorit Chawdhry wrote:
> Hi Aniket,
> 
> On 06:02-20241119, Aniket Limaye wrote:
>> The default j7200 devicetree and k3_avs driver set 2GHz/1GHz frequency
>> for A72/MSMC clks and the OPP_NOM voltage.
>>
>> J7200 SOCs may support OPP_LOW Operating Performance Point:
>> 1GHz/500MHz clks for A72/MSMC and OPP_LOW AVS voltage read from efuse.
>>
>> Hence, add a config check in board_init_f() to select OPP_LOW specs:
>> - Check if OPP_LOW AVS voltage read from efuse is valid.
>> - Use the device IDs and clock IDs (TISCI docs [0]) to find the A72 and
>>    MSMC clock frequencies in the devicetree.
>> - Fixup the clock frequencies in devicetree as per OPP_LOW spec.
>>
>> k3_avs driver programs the OPP_LOW AVS voltage for VDD_CPU through
>> k3_avs_notify_freq() callback from clk_k3.
>>
>> [0]: https://software-dl.ti.com/tisci/esd/latest/5_soc_doc/j7200/clocks.html
>>
>> Signed-off-by: Aniket Limaye <a-limaye at ti.com>
>> ---
> [..]
>> ---
>>   arch/arm/mach-k3/j721e/j721e_init.c | 92 ++++++++++++++++++++++++++++-
>>   1 file changed, 91 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/mach-k3/j721e/j721e_init.c b/arch/arm/mach-k3/j721e/j721e_init.c
>> index e9ed8cb267c..805b28af8e4 100644
>> --- a/arch/arm/mach-k3/j721e/j721e_init.c
>> +++ b/arch/arm/mach-k3/j721e/j721e_init.c
>> @@ -19,6 +19,7 @@
> 
> [..]
>   
>> +#if defined(CONFIG_CPU_V7R) && defined(CONFIG_K3_AVS0)
>> +static int get_clock_index_by_dev_id(ofnode node, u32 dev_id, u32 clk_id)
> 
> I think the following function can be re-usable by other K3 socs too,
> can we put it in some common place instead of j721e_init? Maybe clk-k3.c
> and exported from there?
> 

Yeah that does make sense to do... There are already similar usages, I 
think, in other k3 platforms. Having said that I would like to take that 
up as a separate series since the DT index search is not directly 
related to OPP_LOW Perf Point setting for j7200.

Let me know if you think that the k3 DT clock index search belongs in 
the same series itself...

>> +
>> +static int fdt_fixup_a72ss_clock_frequency(void)
>> +{
>> +	int index, size;
>> +	u32 *rates;
>> +	ofnode node;
>> +
>> +	node = ofnode_by_compatible(ofnode_null(), "ti,am654-rproc");
>> +	if (!ofnode_valid(node)) {
>> +		printf("%s: A72 not found\n", __func__);
>> +		return -ENODEV;
>> +	}
>> +
>> +	rates = fdt_getprop_w(ofnode_to_fdt(node), ofnode_to_offset(node),
>> +			      "assigned-clock-rates", &size);
>> +	if (!rates) {
>> +		printf("%s: Wrong A72 assigned-clocks-rates configuration\n", __func__);
>> +		return -1;
>> +	}
>> +
>> +	/* Update A72 Clock Frequency to OPP_LOW spec */
>> +	index = get_clock_index_by_dev_id(node,
>> +					  DEV_A72SS0_CORE0_0_ID,
>> +					  DEV_A72SS0_CORE0_0_ARM_CLK_CLK_ID);
>> +	if (index < 0 || index >= (size / sizeof(u32))) {
> 
> When would we encounter the second if..?

Assuming you mean:
	index >= (size / sizeof(u32))

The RHS is the count of "assigned-clock-rates" in the node and the LHS 
(index) is the id of the "assigned-clocks".
It's possible (and I see it in a few cases too) that count of 
"assigned-clocks" > count of "assigned-clock-rates". In that case the 
"index" here, even if parsed correctly, could turn out to be outside of 
the bounds of the array "rates". Which should be check against.

Regards,
Aniket

> 
>> +		printf("%s: Wrong A72 assigned-clocks configuration\n", __func__);
>> +		return -1;
>> +	}
>> +	rates[index] = cpu_to_fdt32(1000000000);
>> +	printf("Changed A72 CPU frequency to %dHz in DT\n", 1000000000);
>> +
>> +	/* Update MSMC Clock Frequency to OPP_LOW spec */
>> +	index = get_clock_index_by_dev_id(node,
>> +					  DEV_A72SS0_CORE0_ID,
>> +					  DEV_A72SS0_CORE0_MSMC_CLK_ID);
>> +	if (index < 0 || index >= (size / sizeof(u32))) {
>> +		printf("%s: Wrong A72 assigned-clocks configuration\n", __func__);
>> +		return -1;
>> +	}
>> +	rates[index] = cpu_to_fdt32(500000000);
>> +	printf("Changed MSMC frequency to %dHz in DT\n", 500000000);
>> +
>> +	return 0;
>> +}
>> +#endif
> [..]
> 
> Regards,
> Manorit