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Message-ID: <b8a138ca-9a5b-46e1-8d10-b6d31230f485@nvidia.com>
Date: Mon, 13 Oct 2025 13:59:37 -0700
From: Vedashree Vidwans <vvidwans@...dia.com>
To: Andre Przywara <andre.przywara@....com>
Cc: salman.nabi@....com, lpieralisi@...nel.org, mark.rutland@....com,
sudeep.holla@....com, ardb@...nel.org, chao.gao@...el.com,
linux-arm-kernel@...ts.infradead.org, linux-coco@...ts.linux.dev,
linux-kernel@...r.kernel.org, sdonthineni@...dia.com, vsethi@...dia.com,
vwadekar@...dia.com
Subject: Re: [RFC PATCH 1/3] firmware: smccc: LFA: use smcc 1.2
On 10/10/25 17:02, Andre Przywara wrote:
> External email: Use caution opening links or attachments
>
>
> On Wed, 8 Oct 2025 19:09:05 +0000
> Vedashree Vidwans <vvidwans@...dia.com> wrote:
>
> Hi Vedashree,
>
>> Update driver to use SMCCC 1.2+ version as mentioned in the LFA spec.
>
> ah, right, good catch, one call is using x4, so this must be the v1.2
> calling convention.
>
> Just one small thing below...
>
>> Signed-off-by: Vedashree Vidwans <vvidwans@...dia.com>
>> ---
>> drivers/firmware/smccc/lfa_fw.c | 80 +++++++++++++++++++++++----------
>> 1 file changed, 56 insertions(+), 24 deletions(-)
>>
>> diff --git a/drivers/firmware/smccc/lfa_fw.c b/drivers/firmware/smccc/lfa_fw.c
>> index 1f333237271d8..49f7feb6a211b 100644
>> --- a/drivers/firmware/smccc/lfa_fw.c
>> +++ b/drivers/firmware/smccc/lfa_fw.c
>> @@ -117,9 +117,13 @@ static struct kobject *lfa_dir;
>>
>> static int get_nr_lfa_components(void)
>> {
>> - struct arm_smccc_res res = { 0 };
>> + struct arm_smccc_1_2_regs args = { 0 };
>> + struct arm_smccc_1_2_regs res = { 0 };
>
>>
>> - arm_smccc_1_1_invoke(LFA_1_0_FN_GET_INFO, 0x0, &res);
>> + args.a0 = LFA_1_0_FN_GET_INFO;
>> + args.a1 = 0; /* lfa_info_selector = 0 */
>> +
>> + arm_smccc_1_2_invoke(&args, &res);
>
> I wonder if we can share the same struct for both request and reply?
> arm_smccc_1_2_invoke(&args, &args);
>
> Looks like a lot of stack space used for just a few registers.
> Same for the other occasions where we just do the smc once.
>
> Cheers,
> Andre.
>
Thank you for the suggestion.
Yes, I think using same struct for arguments and results should work.
Regards,
Veda>> if (res.a0 != LFA_SUCCESS)
>> return res.a0;
>>
>> @@ -129,20 +133,23 @@ static int get_nr_lfa_components(void)
>> static int call_lfa_activate(void *data)
>> {
>> struct image_props *attrs = data;
>> - struct arm_smccc_res res = { 0 };
>> + struct arm_smccc_1_2_regs args = { 0 };
>> + struct arm_smccc_1_2_regs res = { 0 };
>> +
>> + args.a0 = LFA_1_0_FN_ACTIVATE;
>> + args.a1 = attrs->fw_seq_id; /* fw_seq_id under consideration */
>> + /*
>> + * As we do not support updates requiring a CPU reset (yet),
>> + * we pass 0 in args.a3 and args.a4, holding the entry point and context
>> + * ID respectively.
>> + * We want to force CPU rendezvous if either cpu_rendezvous or
>> + * cpu_rendezvous_forced is set. The flag value is flipped as
>> + * it is called skip_cpu_rendezvous in the spec.
>> + */
>> + args.a2 = !(attrs->cpu_rendezvous_forced || attrs->cpu_rendezvous);
>>
>> do {
>> - /*
>> - * As we do not support updates requiring a CPU reset (yet),
>> - * we pass 0 in x3 and x4, holding the entry point and context
>> - * ID respectively.
>> - * We want to force CPU rendezvous if either cpu_rendezvous or
>> - * cpu_rendezvous_forced is set. The flag value is flipped as
>> - * it is called skip_cpu_rendezvous in the spec.
>> - */
>> - arm_smccc_1_1_invoke(LFA_1_0_FN_ACTIVATE, attrs->fw_seq_id,
>> - !(attrs->cpu_rendezvous_forced || attrs->cpu_rendezvous),
>> - 0, 0, &res);
>> + arm_smccc_1_2_invoke(&args, &res);
>> } while (res.a0 == 0 && res.a1 == 1);
>>
>> return res.a0;
>> @@ -150,7 +157,8 @@ static int call_lfa_activate(void *data)
>>
>> static int activate_fw_image(struct image_props *attrs)
>> {
>> - struct arm_smccc_res res = { 0 };
>> + struct arm_smccc_1_2_regs args = { 0 };
>> + struct arm_smccc_1_2_regs res = { 0 };
>> int ret;
>>
>> /*
>> @@ -159,8 +167,10 @@ static int activate_fw_image(struct image_props *attrs)
>> * LFA_PRIME/ACTIVATE will need to be called again.
>> * res.a1 will become 0 once the prime/activate process completes.
>> */
>> + args.a0 = LFA_1_0_FN_PRIME;
>> + args.a1 = attrs->fw_seq_id; /* fw_seq_id under consideration */
>> do {
>> - arm_smccc_1_1_invoke(LFA_1_0_FN_PRIME, attrs->fw_seq_id, &res);
>> + arm_smccc_1_2_invoke(&args, &res);
>> if (res.a0 != LFA_SUCCESS) {
>> pr_err("LFA_PRIME failed: %s\n",
>> lfa_error_strings[-res.a0]);
>> @@ -211,13 +221,16 @@ static ssize_t activation_pending_show(struct kobject *kobj,
>> {
>> struct image_props *attrs = container_of(attr, struct image_props,
>> image_attrs[LFA_ATTR_ACT_PENDING]);
>> - struct arm_smccc_res res = { 0 };
>> + struct arm_smccc_1_2_regs args = { 0 };
>> + struct arm_smccc_1_2_regs res = { 0 };
>>
>> /*
>> * Activation pending status can change anytime thus we need to update
>> * and return its current value
>> */
>> - arm_smccc_1_1_invoke(LFA_1_0_FN_GET_INVENTORY, attrs->fw_seq_id, &res);
>> + args.a0 = LFA_1_0_FN_GET_INVENTORY;
>> + args.a1 = attrs->fw_seq_id;
>> + arm_smccc_1_2_invoke(&args, &res);
>> if (res.a0 == LFA_SUCCESS)
>> attrs->activation_pending = !!(res.a3 & BIT(1));
>>
>> @@ -298,9 +311,12 @@ static ssize_t cancel_store(struct kobject *kobj, struct kobj_attribute *attr,
>> {
>> struct image_props *attrs = container_of(attr, struct image_props,
>> image_attrs[LFA_ATTR_CANCEL]);
>> - struct arm_smccc_res res = { 0 };
>> + struct arm_smccc_1_2_regs args = { 0 };
>> + struct arm_smccc_1_2_regs res = { 0 };
>>
>> - arm_smccc_1_1_invoke(LFA_1_0_FN_CANCEL, attrs->fw_seq_id, &res);
>> + args.a0 = LFA_1_0_FN_CANCEL;
>> + args.a1 = attrs->fw_seq_id;
>> + arm_smccc_1_2_invoke(&args, &res);
>>
>> /*
>> * When firmware activation is called with "skip_cpu_rendezvous=1",
>> @@ -395,14 +411,17 @@ static int create_fw_inventory(char *fw_uuid, int seq_id, u32 image_flags)
>>
>> static int create_fw_images_tree(void)
>> {
>> - struct arm_smccc_res res = { 0 };
>> + struct arm_smccc_1_2_regs args = { 0 };
>> + struct arm_smccc_1_2_regs res = { 0 };
>> struct uuid_regs image_uuid;
>> char image_id_str[40];
>> int ret, num_of_components;
>>
>> num_of_components = get_nr_lfa_components();
>> + args.a0 = LFA_1_0_FN_GET_INVENTORY;
>> for (int i = 0; i < num_of_components; i++) {
>> - arm_smccc_1_1_invoke(LFA_1_0_FN_GET_INVENTORY, i, &res);
>> + args.a1 = i; /* fw_seq_id under consideration */
>> + arm_smccc_1_2_invoke(&args, &res);
>> if (res.a0 == LFA_SUCCESS) {
>> image_uuid.uuid_lo = res.a1;
>> image_uuid.uuid_hi = res.a2;
>> @@ -420,10 +439,23 @@ static int create_fw_images_tree(void)
>>
>> static int __init lfa_init(void)
>> {
>> - struct arm_smccc_res res = { 0 };
>> + struct arm_smccc_1_2_regs args = { 0 };
>> + struct arm_smccc_1_2_regs res = { 0 };
>> int err;
>>
>> - arm_smccc_1_1_invoke(LFA_1_0_FN_GET_VERSION, &res);
>> + /* LFA requires SMCCC version >= 1.2 */
>> + if (arm_smccc_get_version() < ARM_SMCCC_VERSION_1_2) {
>> + pr_err("Not supported with SMCCC version %u", arm_smccc_get_version());
>> + return -ENODEV;
>> + }
>> +
>> + if (arm_smccc_1_1_get_conduit() == SMCCC_CONDUIT_NONE) {
>> + pr_err("Invalid SMCCC conduit");
>> + return -ENODEV;
>> + }
>> +
>> + args.a0 = LFA_1_0_FN_GET_VERSION;
>> + arm_smccc_1_2_invoke(&args, &res);
>> if (res.a0 == -LFA_NOT_SUPPORTED) {
>> pr_err("Arm Live Firmware activation(LFA): no firmware agent found\n");
>> return -ENODEV;
>
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