Re: [PATCH 1/2] platform/x86: i2c-multi-instantiate: Add flag for passing fwnode
From: Hans de Goede
Date: Mon Apr 27 2020 - 11:06:22 EST
Hi,
On 4/27/20 3:18 PM, Andy Shevchenko wrote:
On Mon, Apr 27, 2020 at 3:51 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
Hi,
On 4/26/20 7:59 PM, Andy Shevchenko wrote:
On Sun, Apr 26, 2020 at 1:47 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
In some cases the driver for the i2c_client-s which i2c-multi-instantiate
instantiates may need access some fields / methods from to the ACPI fwnode
for which i2c_clients are being instantiated.
An example of this are CPLM3218 ACPI device-s. These contain CPM0 and
CPM1 packages with various information (e.g. register init values) which
the driver needs.
Passing the fwnode through the i2c_board_info struct also gives the
i2c-core access to it, and if we do not pass an IRQ then the i2c-core
will use the fwnode to get an IRQ, see i2c_acpi_get_irq().
I'm wondering, can we rather do it in the same way like we do for
GPIO/APIC case here.
Introduce IRQ_RESOURCE_SHARED (or so) and
case _SHARED:
irq = i2c_acpi_get_irq();
...
?
I think you are miss-understanding the problem. The problem is not that
we want to share the IRQ, the problem is that we want to pass the single
IRQ in the resources to only 1 of the instantiated I2C-clients. But if we
do not pass an IRQ (we leave it at 0) and we do pass the fwnode then
i2c-core-base.c will see that there is an ACPI-node attached to the
device and will call i2c_acpi_get_irq().
Do we know ahead which device should take IRQ resource and which should not?
Can we use current _NONE flag for them?
The problem is not internal to i2c-multi-instantiate.c, the problem
(once we pass a fwnode) is the API between i2c-multi-instantiate.c and
the i2c-core. For the IRQ_RESOURCE_NONE case i2c-multi-instantiate.c
sets board_info.irq to 0, which is the correct way to specify that
we do not have an IRQ, but if don't pass an IRQ then the i2c-core
will try to find one itself. And once we pass the fwnode, then
the "try to find one itself" code will call i2c_acpi_get_irq()
and find the same IRQ for clients we instantiate, leading to
the earlier mentioned IRQ conflict.
<adding Wolfram + i2c lists to the Cc>
We could set board_info.irq to -ENOENT to indicate that there should
not be an irq. But that will get passed to various i2c-drivers, many of
which check for an irq like this:
if (client->irq) {
...
}
We can avoid this, without needing to change all the drivers
by making the i2c-core check for board_info.irq < 0 to skip its
own "try to find IRQ" code and then set client->irq to 0 after
that check, rather then setting it to board_info.irq = -ENOENT.
If we do that then we can unconditionally pass the fwnode in
the i2c-multi-instantiate code.
Regards,
Hans
So the solution is definitely not calling i2c_acpi_get_irq() inside
i2c-multi-instantiate.c we want to avoid the i2c_acpi_get_irq(),
leaving the other 2 clients for the BSG1160 device without an IRQ
and thus avoiding the IRQ mismatch (it is a mismatch because the
drivers do not set the shared flag; and that is ok, we do not want
to share the IRQ, it is just for the accelerometer AFAIK).
This is a problem when there is only an IRQ for 1 of the clients described
in the ACPI device we are instantiating clients for. If we unconditionally
pass the fwnode, then i2c_acpi_get_irq() will assign the same IRQ to all
clients instantiated, leading to kernel-oopses like this (BSG1160 device):
[ 27.340557] genirq: Flags mismatch irq 76. 00002001 (bmc150_magn_event) vs. 00000001 (bmc150_accel_event)
[ 27.340567] Call Trace:
...
So we cannot simply always pass the fwnode. This commit adds a PASS_FWNODE
flag, which can be used to pass the fwnode in cases where we do not have
the IRQ problem and the driver for the instantiated client(s) needs access
to the fwnode.
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
drivers/platform/x86/i2c-multi-instantiate.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/drivers/platform/x86/i2c-multi-instantiate.c b/drivers/platform/x86/i2c-multi-instantiate.c
index 6acc8457866e..dcafb1a29d17 100644
--- a/drivers/platform/x86/i2c-multi-instantiate.c
+++ b/drivers/platform/x86/i2c-multi-instantiate.c
@@ -20,6 +20,8 @@
#define IRQ_RESOURCE_GPIO 1
#define IRQ_RESOURCE_APIC 2
+#define PASS_FWNODE BIT(2)
+
struct i2c_inst_data {
const char *type;
unsigned int flags;
@@ -93,6 +95,10 @@ static int i2c_multi_inst_probe(struct platform_device *pdev)
snprintf(name, sizeof(name), "%s-%s.%d", dev_name(dev),
inst_data[i].type, i);
board_info.dev_name = name;
+
+ if (inst_data[i].flags & PASS_FWNODE)
+ board_info.fwnode = dev->fwnode;
+
switch (inst_data[i].flags & IRQ_RESOURCE_TYPE) {
case IRQ_RESOURCE_GPIO:
ret = acpi_dev_gpio_irq_get(adev, inst_data[i].irq_idx);
--
2.26.0