[Patch v2 1/3] firmware: google: Release devices before unregistering the bus

[Patch v2 1/3] firmware: google: Release devices before unregistering the bus

[patrick.rudolph]

From: Patrick Rudolph <patrick.rudolph@9elements.com>

Fix a bug where the kernel module can't be loaded after it has been
unloaded as the devices are still present and conflicting with the
to be created coreboot devices.

Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
 drivers/firmware/google/coreboot_table.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmware/google/coreboot_table.c
index 8d132e4f008a..0205987a4fd4 100644
--- a/drivers/firmware/google/coreboot_table.c
+++ b/drivers/firmware/google/coreboot_table.c
@@ -163,8 +163,15 @@ static int coreboot_table_probe(struct platform_device *pdev)
 	return ret;
 }
 
+static int __cb_dev_unregister(struct device *dev, void *dummy)
+{
+	device_unregister(dev);
+	return 0;
+}
+
 static int coreboot_table_remove(struct platform_device *pdev)
 {
+	bus_for_each_dev(&coreboot_bus_type, NULL, NULL, __cb_dev_unregister);
 	bus_unregister(&coreboot_bus_type);
 	return 0;
 }
-- 
2.21.0

[Patch v2 2/3] firmware: google: Unregister driver_info on failure and exit in gsmi

[patrick.rudolph]

From: Arthur Heymans <arthur@aheymans.xyz>

Fix a bug where the kernel module couldn't be loaded after unloading,
as the platform driver wasn't released on exit.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
 drivers/firmware/google/gsmi.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/firmware/google/gsmi.c b/drivers/firmware/google/gsmi.c
index edaa4e5d84ad..974c769b75cf 100644
--- a/drivers/firmware/google/gsmi.c
+++ b/drivers/firmware/google/gsmi.c
@@ -1016,6 +1016,9 @@ static __init int gsmi_init(void)
 	dma_pool_destroy(gsmi_dev.dma_pool);
 	platform_device_unregister(gsmi_dev.pdev);
 	pr_info("gsmi: failed to load: %d\n", ret);
+#ifdef CONFIG_PM
+	platform_driver_unregister(&gsmi_driver_info);
+#endif
 	return ret;
 }
 
@@ -1037,6 +1040,9 @@ static void __exit gsmi_exit(void)
 	gsmi_buf_free(gsmi_dev.name_buf);
 	dma_pool_destroy(gsmi_dev.dma_pool);
 	platform_device_unregister(gsmi_dev.pdev);
+#ifdef CONFIG_PM
+	platform_driver_unregister(&gsmi_driver_info);
+#endif
 }
 
 module_init(gsmi_init);
-- 
2.21.0

[Patch v2 3/3] firmware: google: Probe for a GSMI handler in firmware

[patrick.rudolph]

From: Arthur Heymans <arthur@aheymans.xyz>

Currently this driver is loaded if the DMI string matches coreboot
and has a proper smi_command in the ACPI FADT table, but a GSMI handler in
SMM is an optional feature in coreboot.

So probe for a SMM GSMI handler before initializing the driver.
If the smihandler leaves the calling argument in %eax in the SMM save state
untouched that generally means the is no handler for GSMI.

Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
---
 drivers/firmware/google/gsmi.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/firmware/google/gsmi.c b/drivers/firmware/google/gsmi.c
index 974c769b75cf..5b2011ebbe26 100644
--- a/drivers/firmware/google/gsmi.c
+++ b/drivers/firmware/google/gsmi.c
@@ -76,6 +76,7 @@
 #define GSMI_CMD_LOG_S0IX_RESUME	0x0b
 #define GSMI_CMD_CLEAR_CONFIG		0x20
 #define GSMI_CMD_HANDSHAKE_TYPE		0xC1
+#define GSMI_CMD_RESERVED		0xff
 
 /* Magic entry type for kernel events */
 #define GSMI_LOG_ENTRY_TYPE_KERNEL     0xDEAD
@@ -746,6 +747,7 @@ MODULE_DEVICE_TABLE(dmi, gsmi_dmi_table);
 static __init int gsmi_system_valid(void)
 {
 	u32 hash;
+	u16 cmd, result;
 
 	if (!dmi_check_system(gsmi_dmi_table))
 		return -ENODEV;
@@ -780,6 +782,23 @@ static __init int gsmi_system_valid(void)
 		return -ENODEV;
 	}
 
+	/* Test the smihandler with a bogus command. If it leaves the
+	 * calling argument in %ax untouched, there is no handler for
+	 * GSMI commands.
+	 */
+	cmd = GSMI_CALLBACK | GSMI_CMD_RESERVED << 8;
+	asm volatile (
+		"outb %%al, %%dx\n\t"
+		: "=a" (result)
+		: "0" (cmd),
+		  "d" (acpi_gbl_FADT.smi_command)
+		: "memory", "cc"
+		);
+	if (cmd == result) {
+		pr_info("gsmi: no gsmi handler in firmware\n");
+		return -ENODEV;
+	}
+
 	/* Found */
 	return 0;
 }
-- 
2.21.0

Re: [Patch v2 1/3] firmware: google: Release devices before unregistering the bus

[Greg Kroah-Hartman]

On Mon, Nov 18, 2019 at 09:38:58AM +0100, patrick.rudolph@9elements.com wrote:
> From: Patrick Rudolph <patrick.rudolph@9elements.com>
> 
> Fix a bug where the kernel module can't be loaded after it has been
> unloaded as the devices are still present and conflicting with the
> to be created coreboot devices.
> 
> Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
> ---
>  drivers/firmware/google/coreboot_table.c | 7 +++++++
>  1 file changed, 7 insertions(+)

You forgot to document what changed from v1 of this patch and/or series
somewhere :(

Usually it just goes below the --- line on each patch.

Can you fix that up and send a v3 of this series?

thanks

greg k-h