[PATCH 1/2] mfd: intel-lpss: fall back to polling when no usable IRQ

[PATCH 1/2] mfd: intel-lpss: fall back to polling when no usable IRQ

[Samuel Tirwa]

On platforms such as the HONOR MagicBook Pro 14 (2025) (Intel Core Ultra 9 285H)
the firmware ACPI tables report the Intel LPSS I2C controllers' PCI INTx line as
not connected (Interrupt Line = 0xff, GSI 255) and do not grant MSI control
through _OSC.  As a result acpi_pci_irq_enable() sets dev->irq to
IRQ_NOTCONNECTED and intel_lpss_probe() rejects it, so all three I2C
controllers (8086:7778/7779/777a) fail to probe with -ENOTCONN and the
touchpad/touchscreen are never exposed.

Treat IRQ_NOTCONNECTED as 'no interrupt available' and pass 0 as the IRQ base
to the child devices instead of failing.  The DesignWare I2C driver already
supports a polling mode when no IRQ resource is present, which keeps the
controllers functional on these firmwares.

Signed-off-by: Samuel Tirwa <samuel.tirwa@web.de>
---
 drivers/mfd/intel-lpss.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c
index f71e076..f785d5d 100644
--- a/drivers/mfd/intel-lpss.c
+++ b/drivers/mfd/intel-lpss.c
@@ -1,5 +1,6 @@
 #include <linux/mfd/core.h>
 #include <linux/module.h>
+#include <linux/interrupt.h>
 
 int intel_lpss_probe(struct device *dev,
                      const struct intel_lpss_platform_info *info)
@@ -7,10 +8,17 @@ int intel_lpss_probe(struct device *dev,
 	struct intel_lpss *lpss;
 	int ret;
 
-	if (!info || !info->mem || info->irq <= 0)
+	if (!info || !info->mem)
 		return -EINVAL;
 
-	if (info->irq < 0)
+	/*
+	 * Firmware on some platforms (e.g. HONOR MagicBook Pro 14 2025)
+	 * reports the LPSS PCI INTx line as not connected (IRQ_NOTCONNECTED).
+	 * Fall back to polling mode in that case instead of failing probe.
+	 */
+	if (info->irq == IRQ_NOTCONNECTED)
+		info->irq = 0;
+	else if (info->irq < 0)
 		return info->irq;
 
 	lpss = devm_kzalloc(dev, sizeof(*lpss), GFP_KERNEL);
-- 
2.56.0.windows.4

[PATCH 2/2] i2c: designware: use polling when IRQ resource is 0

[Samuel Tirwa]

When an Intel LPSS I2C controller has no usable interrupt (firmware
reports PCI INTx as not connected), intel-lpss passes 0 as the IRQ base,
which leaves the child device with an IRQ resource whose start is 0.
platform_get_irq_optional() then returns 0 instead of -ENXIO, so the
DesignWare driver never enabled ACCESS_POLLING and request_irq(0, ...)
failed.

Treat an IRQ number of 0 the same as 'no IRQ resource' and enable
polling mode.

Signed-off-by: Samuel Tirwa <samuel.tirwa@web.de>
---
 drivers/i2c/busses/i2c-designware-platdrv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-designware-platdrv.c b/drivers/i2c/busses/i2c-designware-platdrv.c
index ca63b74..035ec92 100644
--- a/drivers/i2c/busses/i2c-designware-platdrv.c
+++ b/drivers/i2c/busses/i2c-designware-platdrv.c
@@ -4,7 +4,7 @@ static int dw_i2c_plat_probe(struct platform_device *pdev)
 	int irq, ret;
 
 	irq = platform_get_irq_optional(pdev, 0);
-	if (irq == -ENXIO)
+	if (irq == -ENXIO || irq == 0)
 		flags |= ACCESS_POLLING;
 	else if (irq < 0)
 		return irq;
-- 
2.56.0.windows.4

Re: [PATCH 1/2] mfd: intel-lpss: fall back to polling when no usable IRQ

[Lee Jones]

--- checkpatch.pl (1 issue) ---
Line 3: WARNING: Prefer a maximum 75 chars per line (possible unwrapped commit description?)
----------------------------------

On Tue, 03 Nov 2026, Samuel Tirwa wrote:

> On platforms such as the HONOR MagicBook Pro 14 (2025) (Intel Core Ultra 9 285H)
> the firmware ACPI tables report the Intel LPSS I2C controllers' PCI INTx line as

These lines look excessively long.

> not connected (Interrupt Line = 0xff, GSI 255) and do not grant MSI control
> through _OSC.  As a result acpi_pci_irq_enable() sets dev->irq to
> IRQ_NOTCONNECTED and intel_lpss_probe() rejects it, so all three I2C
> controllers (8086:7778/7779/777a) fail to probe with -ENOTCONN and the
> touchpad/touchscreen are never exposed.
>
> Treat IRQ_NOTCONNECTED as 'no interrupt available' and pass 0 as the IRQ base
> to the child devices instead of failing.  The DesignWare I2C driver already
> supports a polling mode when no IRQ resource is present, which keeps the
> controllers functional on these firmwares.
>
> Signed-off-by: Samuel Tirwa <samuel.tirwa@web.de>
> ---
>  drivers/mfd/intel-lpss.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c
> index f71e076..f785d5d 100644
> --- a/drivers/mfd/intel-lpss.c
> +++ b/drivers/mfd/intel-lpss.c
> @@ -1,5 +1,6 @@
>  #include <linux/mfd/core.h>
>  #include <linux/module.h>
> +#include <linux/interrupt.h>

Alphabetical.

>  int intel_lpss_probe(struct device *dev,
>                       const struct intel_lpss_platform_info *info)
> @@ -7,10 +8,17 @@ int intel_lpss_probe(struct device *dev,
>  	struct intel_lpss *lpss;
>  	int ret;
>
> -	if (!info || !info->mem || info->irq <= 0)
> +	if (!info || !info->mem)
>  		return -EINVAL;
>
> -	if (info->irq < 0)
> +	/*
> +	 * Firmware on some platforms (e.g. HONOR MagicBook Pro 14 2025)
> +	 * reports the LPSS PCI INTx line as not connected (IRQ_NOTCONNECTED).
> +	 * Fall back to polling mode in that case instead of failing probe.
> +	 */
> +	if (info->irq == IRQ_NOTCONNECTED)
> +		info->irq = 0;

Does this even compile?  Isn't 'info' declared 'const'?

Moreover, mfd_add_devices() inside intel_lpss_probe() passes 'info->irq' as
the 'irq_base' alongside a hardcoded 'n_resources = 2' on the 'mfd_cell'
definitions (which include DEFINE_RES_IRQ(0)).  Simply passing '0' as
'irq_base' does not omit the 'IORESOURCE_IRQ' resource - it just shifts the
child's IRQ resource to '0', whereas 'i2c-designware-platdrv' only enters
polling mode when 'platform_get_irq_optional()' returns '-ENXIO' (no IRQ
resource present), or should this be handled in the glue layer or by adjusting
how the cell resources are populated?

How was this tested?

> +	else if (info->irq < 0)
>  		return info->irq;
>
>  	lpss = devm_kzalloc(dev, sizeof(*lpss), GFP_KERNEL);
> -- 
> 2.56.0.windows.4
>

-- 
Lee Jones

[PATCH 1/2] mfd: intel-lpss: fall back to polling when no usable IRQ

[Samuel Tirwa]

From: Fix Agent <fix@kernel.org>

On platforms such as the HONOR MagicBook Pro 14 (2025) (Intel Core Ultra 9 285H)
the firmware ACPI tables report the Intel LPSS I2C controllers' PCI INTx line as
not connected (Interrupt Line = 0xff, GSI 255) and do not grant MSI control
through _OSC.  As a result acpi_pci_irq_enable() sets dev->irq to
IRQ_NOTCONNECTED and intel_lpss_probe() rejects it, so all three I2C
controllers (8086:7778/7779/777a) fail to probe with -ENOTCONN and the
touchpad/touchscreen are never exposed.

Treat IRQ_NOTCONNECTED as 'no interrupt available' and pass 0 as the IRQ base
to the child devices instead of failing.  The DesignWare I2C driver already
supports a polling mode when no IRQ resource is present, which keeps the
controllers functional on these firmwares.

Signed-off-by: Fix Agent <fix@kernel.org>
---
 drivers/mfd/intel-lpss.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/mfd/intel-lpss.c b/drivers/mfd/intel-lpss.c
index f71e076..f785d5d 100644
--- a/drivers/mfd/intel-lpss.c
+++ b/drivers/mfd/intel-lpss.c
@@ -1,5 +1,6 @@
 #include <linux/mfd/core.h>
 #include <linux/module.h>
+#include <linux/interrupt.h>
 
 int intel_lpss_probe(struct device *dev,
                      const struct intel_lpss_platform_info *info)
@@ -7,10 +8,17 @@ int intel_lpss_probe(struct device *dev,
 	struct intel_lpss *lpss;
 	int ret;
 
-	if (!info || !info->mem || info->irq <= 0)
+	if (!info || !info->mem)
 		return -EINVAL;
 
-	if (info->irq < 0)
+	/*
+	 * Firmware on some platforms (e.g. HONOR MagicBook Pro 14 2025)
+	 * reports the LPSS PCI INTx line as not connected (IRQ_NOTCONNECTED).
+	 * Fall back to polling mode in that case instead of failing probe.
+	 */
+	if (info->irq == IRQ_NOTCONNECTED)
+		info->irq = 0;
+	else if (info->irq < 0)
 		return info->irq;
 
 	lpss = devm_kzalloc(dev, sizeof(*lpss), GFP_KERNEL);
-- 
2.56.0.windows.4