Some SoCs (e.g. AST2700) expose more than one physical LPC controller
instance (e.g. lpc0@14c31000, lpc1@14c32000, plus pcie_lpc0@12c19000
and pcie_lpc1@12c19800 for the PCIe-facing path), each instantiating
its own independent set of KCS1-KCS4 channels using identical
IDR/ODR/STR register offsets.
kcs_bmc_device::channel currently serves two purposes at once:
1. Selecting which HICR0/HICR2/HICRB bit-group to touch within a
single LPC controller's register file. aspeed_kcs_of_get_channel()
derives this purely from the KCS node's register offset, yielding
values 1..4.
2. Naming the misc chardev (/dev/ipmi-kcsN) exposed to userspace,
which must be unique system-wide. kcs_bmc_cdev_ipmi.c uses
"ipmi-kcs%u".
Both happen to be the same value only because this driver has only
ever had to support SoCs with a single LPC controller. On AST2700, KCS1
on every LPC controller computes to the same channel number, and
whichever instance probes second fails outright:
sysfs: cannot create duplicate filename
'/devices/virtual/misc/ipmi-kcs1'
ast-kcs-bmc 14c32024.kcs: Unable to register device: -17
ast-kcs-bmc 14c32024.kcs: Failed to add chardev for KCS channel 1: -17
ast-kcs-bmc: probe of 14c32024.kcs failed with error -17
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 aspeed_kcs_of_get_bank(), which keeps a
driver-private, mutex-protected list keyed by the LPC controller's
device_node pointer and assigns bank indices in
first-seen-during-probe order. SoCs with a single LPC controller
always end up with bank 0, so /dev/ipmi-kcsN naming is unchanged for
all existing boards, and no devicetree or binding changes are required
for any platform.
Signed-off-by: Yu-Che Hsieh <[email protected]>
---
Changes in v3:
- Drop the of_alias_get_id()-based bank derivation and the dt-bindings
patch that documented it.
- Replace with dynamic bank discovery: the first time an LPC
controller's device_node is seen during probe, assign it the next
available bank index and remember it in a driver-private list. This
needs no DT/binding changes at all.
Link to v2:
https://lore.kernel.org/r/20260813-upstream_kcs_multiple_lpc-v2-0-775b1db3f...@aspeedtech.com
Changes in v2:
- Drop the RFC tag, per Lee Jones' feedback.
- Keep the alias-based bank-numbering approach unchanged.
Link to v1:
https://lore.kernel.org/r/20260723-upstream_kcs_multiple_lpc-v1-0-d918b5270...@aspeedtech.com
---
drivers/char/ipmi/kcs_bmc_aspeed.c | 71 ++++++++++++++++++++++++++++++++------
1 file changed, 61 insertions(+), 10 deletions(-)
diff --git a/drivers/char/ipmi/kcs_bmc_aspeed.c
b/drivers/char/ipmi/kcs_bmc_aspeed.c
index a13a3470c17a..751f477c09e0 100644
--- a/drivers/char/ipmi/kcs_bmc_aspeed.c
+++ b/drivers/char/ipmi/kcs_bmc_aspeed.c
@@ -10,8 +10,10 @@
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/irq.h>
+#include <linux/list.h>
#include <linux/mfd/syscon.h>
#include <linux/module.h>
+#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/platform_device.h>
@@ -125,6 +127,8 @@ 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 +171,7 @@ 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 +236,7 @@ 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 +319,7 @@ 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 +351,7 @@ 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 +362,7 @@ 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 +378,7 @@ 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 +439,7 @@ 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 +457,7 @@ 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 +530,47 @@ static int aspeed_kcs_of_get_channel(struct
platform_device *pdev)
return -EINVAL;
}
+struct aspeed_kcs_bank {
+ struct device_node *lpc_np;
+ struct list_head entry;
+};
+
+static DEFINE_MUTEX(aspeed_kcs_bank_lock);
+static LIST_HEAD(aspeed_kcs_banks);
+
+/*
+ * Assign each distinct LPC controller device_node a stable bank index the
+ * first time it's seen, so that KCS devices instantiated from different LPC
+ * controllers on the same SoC (e.g. AST2700) don't collide on the same
+ * global kcs_bmc_device::channel value.
+ */
+static int aspeed_kcs_of_get_bank(struct device_node *lpc_np)
+{
+ struct aspeed_kcs_bank *bank;
+ int index = 0;
+
+ mutex_lock(&aspeed_kcs_bank_lock);
+
+ list_for_each_entry(bank, &aspeed_kcs_banks, entry) {
+ if (bank->lpc_np == lpc_np)
+ goto out;
+ index++;
+ }
+
+ bank = kzalloc(sizeof(*bank), GFP_KERNEL);
+ if (!bank) {
+ mutex_unlock(&aspeed_kcs_bank_lock);
+ return -ENOMEM;
+ }
+
+ bank->lpc_np = lpc_np;
+ list_add_tail(&bank->entry, &aspeed_kcs_banks);
+
+out:
+ mutex_unlock(&aspeed_kcs_bank_lock);
+ return index;
+}
+
static int
aspeed_kcs_of_get_io_address(struct platform_device *pdev, u32 addrs[2])
{
@@ -559,7 +604,7 @@ 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 +620,10 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
if (channel < 0)
return channel;
+ bank = aspeed_kcs_of_get_bank(np);
+ if (bank < 0)
+ return bank;
+
nr_addrs = aspeed_kcs_of_get_io_address(pdev, addrs);
if (nr_addrs < 0)
return nr_addrs;
@@ -590,9 +639,11 @@ 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;
---
base-commit: f0e6f20cb52b14c2c441f04e21cef0c95d498cac
change-id: 20260722-upstream_kcs_multiple_lpc-735942211508
Best regards,
--
Yu-Che Hsieh <[email protected]>
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