[PATCH RFC 2/2] ipmi: kcs_bmc_aspeed: Support multiple LPC controller instances
From: Yu-Che Hsieh
Date: Thu Jul 23 2026 - 01:34:19 EST
Some SoCs (e.g. AST2700) expose more than one physical LPC controller,
each instantiating its own independent set of KCS0-KCS3 channels using
identical IDR/ODR/STR register offsets. kcs_bmc_device::channel is
currently overloaded to serve two distinct purposes: selecting which
HICR0/HICR2/HICRB bit-group to touch within a single LPC controller's
register file, and naming the misc chardev (/dev/ipmi-kcsN) exposed to
userspace, which must be unique system-wide. The two purposes happen
to share the same value only because the driver has so far only had
to support SoCs with a single LPC controller. On a multi-controller
SoC, KCS0 on every LPC controller computes to the same channel number,
and whichever instance probes second fails to register its chardev.
Split the two roles: keep a new driver-private `channel` field (1..4)
in struct aspeed_kcs_bmc for register access, leaving all the
HICR/IBFIE/LPCxE switch statements operating on it, and derive
kcs_bmc_device::channel as `bank * KCS_CHANNEL_MAX + channel`, where
`bank` identifies which LPC controller instance a KCS device belongs
to.
`bank` is obtained from an optional "lpcN" alias on the LPC controller
node via of_alias_get_id(), following the same convention already used
by mmc/i2c/spi/serial for instance numbering. SoCs with a single LPC
controller, and existing DTs that don't declare the alias, fall back
to bank 0, so /dev/ipmi-kcsN naming is unchanged for all existing
boards.
Signed-off-by: Yu-Che Hsieh <yc_hsieh@xxxxxxxxxxxxxx>
---
drivers/char/ipmi/kcs_bmc_aspeed.c | 37 +++++++++++++++++++++++++++----------
1 file changed, 27 insertions(+), 10 deletions(-)
diff --git a/drivers/char/ipmi/kcs_bmc_aspeed.c b/drivers/char/ipmi/kcs_bmc_aspeed.c
index a13a3470c17a..591c11a44503 100644
--- a/drivers/char/ipmi/kcs_bmc_aspeed.c
+++ b/drivers/char/ipmi/kcs_bmc_aspeed.c
@@ -125,6 +125,8 @@ struct aspeed_kcs_bmc {
bool remove;
struct timer_list timer;
} obe;
+
+ u32 channel;
};
static inline struct aspeed_kcs_bmc *to_aspeed_kcs_bmc(struct kcs_bmc_device *kcs_bmc)
@@ -167,7 +169,7 @@ static void aspeed_kcs_outb(struct kcs_bmc_device *kcs_bmc, u32 reg, u8 data)
if (priv->upstream_irq.mode != aspeed_kcs_irq_serirq)
return;
- switch (kcs_bmc->channel) {
+ switch (priv->channel) {
case 1:
switch (priv->upstream_irq.id) {
case 12:
@@ -232,7 +234,7 @@ static int aspeed_kcs_set_address(struct kcs_bmc_device *kcs_bmc, u32 addrs[2],
if (WARN_ON(nr_addrs < 1 || nr_addrs > 2))
return -EINVAL;
- switch (priv->kcs_bmc.channel) {
+ switch (priv->channel) {
case 1:
regmap_update_bits(priv->map, LPC_HICR4, LPC_HICR4_LADR12AS, 0);
regmap_write(priv->map, LPC_LADR12H, addrs[0] >> 8);
@@ -315,7 +317,7 @@ static int aspeed_kcs_config_upstream_irq(struct aspeed_kcs_bmc *priv, u32 id, u
priv->upstream_irq.mode = aspeed_kcs_irq_serirq;
priv->upstream_irq.id = id;
- switch (priv->kcs_bmc.channel) {
+ switch (priv->channel) {
case 1:
/* Needs IRQxE1 rather than (ID1IRQX, SEL1IRQX, IRQXE1) before AST2600 A3 */
break;
@@ -347,7 +349,7 @@ static int aspeed_kcs_config_upstream_irq(struct aspeed_kcs_bmc *priv, u32 id, u
default:
dev_warn(priv->kcs_bmc.dev,
"SerIRQ configuration not supported on KCS channel %d\n",
- priv->kcs_bmc.channel);
+ priv->channel);
return -EINVAL;
}
@@ -358,7 +360,7 @@ static void aspeed_kcs_enable_channel(struct kcs_bmc_device *kcs_bmc, bool enabl
{
struct aspeed_kcs_bmc *priv = to_aspeed_kcs_bmc(kcs_bmc);
- switch (kcs_bmc->channel) {
+ switch (priv->channel) {
case 1:
regmap_update_bits(priv->map, LPC_HICR0, LPC_HICR0_LPC1E, enable * LPC_HICR0_LPC1E);
return;
@@ -374,7 +376,7 @@ static void aspeed_kcs_enable_channel(struct kcs_bmc_device *kcs_bmc, bool enabl
regmap_update_bits(priv->map, LPC_HICRB, LPC_HICRB_LPC4E, enable * LPC_HICRB_LPC4E);
return;
default:
- pr_warn("%s: Unsupported channel: %d", __func__, kcs_bmc->channel);
+ pr_warn("%s: Unsupported channel: %d", __func__, priv->channel);
return;
}
}
@@ -435,7 +437,7 @@ static void aspeed_kcs_irq_mask_update(struct kcs_bmc_device *kcs_bmc, u8 mask,
if (mask & KCS_BMC_EVENT_TYPE_IBF) {
const bool enable = !!(state & KCS_BMC_EVENT_TYPE_IBF);
- switch (kcs_bmc->channel) {
+ switch (priv->channel) {
case 1:
regmap_update_bits(priv->map, LPC_HICR2, LPC_HICR2_IBFIE1,
enable * LPC_HICR2_IBFIE1);
@@ -453,7 +455,7 @@ static void aspeed_kcs_irq_mask_update(struct kcs_bmc_device *kcs_bmc, u8 mask,
enable * LPC_HICRB_IBFIE4);
return;
default:
- pr_warn("%s: Unsupported channel: %d", __func__, kcs_bmc->channel);
+ pr_warn("%s: Unsupported channel: %d", __func__, priv->channel);
return;
}
}
@@ -526,6 +528,17 @@ static int aspeed_kcs_of_get_channel(struct platform_device *pdev)
return -EINVAL;
}
+static int aspeed_kcs_of_get_bank(struct device_node *lpc_np)
+{
+ int id;
+
+ id = of_alias_get_id(lpc_np, "lpc");
+ if (id < 0)
+ return 0;
+
+ return id;
+}
+
static int
aspeed_kcs_of_get_io_address(struct platform_device *pdev, u32 addrs[2])
{
@@ -559,7 +572,7 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
struct device_node *np;
bool have_upstream_irq;
u32 upstream_irq[2];
- int rc, channel;
+ int rc, channel, bank;
int nr_addrs;
u32 addrs[2];
@@ -575,6 +588,8 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
if (channel < 0)
return channel;
+ bank = aspeed_kcs_of_get_bank(np);
+
nr_addrs = aspeed_kcs_of_get_io_address(pdev, addrs);
if (nr_addrs < 0)
return nr_addrs;
@@ -590,9 +605,11 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
if (!priv)
return -ENOMEM;
+ priv->channel = channel;
+
kcs_bmc = &priv->kcs_bmc;
kcs_bmc->dev = &pdev->dev;
- kcs_bmc->channel = channel;
+ kcs_bmc->channel = bank * KCS_CHANNEL_MAX + channel;
kcs_bmc->ioreg = ast_kcs_bmc_ioregs[channel - 1];
kcs_bmc->ops = &aspeed_kcs_ops;
--
2.34.1