I3C devices like DIMMs over SPD use SETAASA[1] for bus discovery instead of
SETDASA. Add a new routine for I3C host controller drivers to use. If the
I3C slave on the bus is an SPD device, skip the regular DAA process.

According to the SPD spec[2], use SETAASA for bus discovery, and avoid
sending RSTDAA and DISEC, as they are considered illegal. Skip this entire
process if the slave is SPD-compliant, as indicated by the "jdec_spd" flag
from the BIOS.

[1] SETAASA is introduced in MIPI v1.1.1 specification.
[2] https://www.jedec.org/system/files/docs/JESD300-5B.01.pdf
(section 2.4 and 2.6.3)

Co-developed-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
---
 drivers/i3c/master.c               | 32 +++++++++++++++++++++++++++++-
 drivers/i3c/master/dw-i3c-master.c |  1 +
 include/linux/i3c/ccc.h            |  1 +
 include/linux/i3c/master.h         |  1 +
 4 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index 8f37dcaa1efe..2f06f168ef82 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -1657,6 +1657,21 @@ i3c_master_register_new_i3c_devs(struct i3c_master_controller *master)
 	}
 }
 
+static int i3c_master_setaasa_locked(struct i3c_master_controller *master)
+{
+	struct i3c_ccc_cmd_dest dest;
+	struct i3c_ccc_cmd cmd;
+	int ret;
+
+	i3c_ccc_cmd_dest_init(&dest, I3C_BROADCAST_ADDR, 0);
+	i3c_ccc_cmd_init(&cmd, false, I3C_CCC_SETAASA, &dest, 1);
+
+	ret = i3c_master_send_ccc_cmd_locked(master, &cmd);
+	i3c_ccc_cmd_dest_cleanup(&dest);
+
+	return ret;
+}
+
 static int i3c_master_add_spd_dev(struct i3c_master_controller *master,
 				  struct i3c_dev_boardinfo *boardinfo)
 {
@@ -1684,6 +1699,10 @@ static int i3c_master_add_spd_dev(struct i3c_master_controller *master,
 		i3cdev->info.pid = i3cdev->boardinfo->pid;
 		i3cdev->info.dyn_addr = i3cdev->boardinfo->init_dyn_addr;
 
+		ret = i3c_master_setaasa_locked(master);
+		if (ret)
+			goto err_free_dev;
+
 		i3c_bus_normaluse_lock(&master->bus);
 		i3c_master_register_new_i3c_devs(master);
 		i3c_bus_normaluse_unlock(&master->bus);
@@ -1907,7 +1926,14 @@ static int i3c_master_bus_init(struct i3c_master_controller *master)
 		goto err_bus_cleanup;
 	}
 
-	i3c_master_add_spd_dev(master, i3cboardinfo);
+	/*
+	 * If the I3C slave on the bus is SPD device, then do not follow the regular
+	 * DAA process. Also, as per SPD spec SETAASA is required for the bus discovery
+	 * and sending RSTDAA and DISEC is considered as illegal. So skip the entire process
+	 * if the jdec_spd flag has been identified from the BIOS.
+	 */
+	if (master->jdec_spd)
+		return i3c_master_add_spd_dev(master, i3cboardinfo);
 
 	if (master->ops->set_speed) {
 		ret = master->ops->set_speed(master, I3C_OPEN_DRAIN_SLOW_SPEED);
@@ -2311,6 +2337,10 @@ static int i3c_acpi_configure_master(struct i3c_master_controller *master)
 		return -ENODEV;
 	}
 
+	status = acpi_evaluate_object(master->ahandle, "_STR", NULL, NULL);
+	if (ACPI_SUCCESS(status))
+		master->jdec_spd = true;
+
 	num_dev = device_get_child_node_count(dev);
 	if (!num_dev) {
 		dev_err(&master->dev, "Error: no child node present\n");
diff --git a/drivers/i3c/master/dw-i3c-master.c b/drivers/i3c/master/dw-i3c-master.c
index d44b771d03e1..dc701275485a 100644
--- a/drivers/i3c/master/dw-i3c-master.c
+++ b/drivers/i3c/master/dw-i3c-master.c
@@ -282,6 +282,7 @@ static bool dw_i3c_master_supports_ccc_cmd(struct i3c_master_controller *m,
 	case I3C_CCC_GETSTATUS:
 	case I3C_CCC_GETMXDS:
 	case I3C_CCC_GETHDRCAP:
+	case I3C_CCC_SETAASA:
 		return true;
 	default:
 		return false;
diff --git a/include/linux/i3c/ccc.h b/include/linux/i3c/ccc.h
index ad59a4ae60d1..a145d766ab6f 100644
--- a/include/linux/i3c/ccc.h
+++ b/include/linux/i3c/ccc.h
@@ -32,6 +32,7 @@
 #define I3C_CCC_DEFSLVS			I3C_CCC_ID(0x8, true)
 #define I3C_CCC_ENTTM			I3C_CCC_ID(0xb, true)
 #define I3C_CCC_ENTHDR(x)		I3C_CCC_ID(0x20 + (x), true)
+#define I3C_CCC_SETAASA			I3C_CCC_ID(0x29, true)
 
 /* Unicast-only commands */
 #define I3C_CCC_SETDASA			I3C_CCC_ID(0x7, false)
diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
index 367faf7c4bf3..cd8390d8b469 100644
--- a/include/linux/i3c/master.h
+++ b/include/linux/i3c/master.h
@@ -516,6 +516,7 @@ struct i3c_master_controller {
 	const struct i3c_master_controller_ops *ops;
 	unsigned int secondary : 1;
 	unsigned int init_done : 1;
+	unsigned int jdec_spd : 1;
 	unsigned int hotjoin: 1;
 	struct {
 		struct list_head i3c;
-- 
2.34.1

Hi

On 11/8/24 9:33 AM, Shyam Sundar S K wrote:
> @@ -1907,7 +1926,14 @@ static int i3c_master_bus_init(struct i3c_master_controller *master)
>   		goto err_bus_cleanup;
>   	}
>   
> -	i3c_master_add_spd_dev(master, i3cboardinfo);
> +	/*
> +	 * If the I3C slave on the bus is SPD device, then do not follow the regular
> +	 * DAA process. Also, as per SPD spec SETAASA is required for the bus discovery
> +	 * and sending RSTDAA and DISEC is considered as illegal. So skip the entire process
> +	 * if the jdec_spd flag has been identified from the BIOS.
> +	 */
> +	if (master->jdec_spd)
> +		return i3c_master_add_spd_dev(master, i3cboardinfo);
>   
This looks wrong the previous patch adds unconditional call to 
i3c_master_add_spd_dev() and this patch makes it conditional. Can 
previous patch then cause a regression if applied without this one?

>   	if (master->ops->set_speed) {
>   		ret = master->ops->set_speed(master, I3C_OPEN_DRAIN_SLOW_SPEED);
> @@ -2311,6 +2337,10 @@ static int i3c_acpi_configure_master(struct i3c_master_controller *master)
>   		return -ENODEV;
>   	}
>   
> +	status = acpi_evaluate_object(master->ahandle, "_STR", NULL, NULL);
> +	if (ACPI_SUCCESS(status))
> +		master->jdec_spd = true;
> +

I'm still suspicious about this one when existence of _STR for the host 
controller causes normal bus initialization to be skipped. I.e. like below.

Device (I3C0)
{
	_STR ("My I3C Host Controller")
...