linux-kernel - Re: [RFC][Patch] IBM Real-Time "SMI Free" mode driver -v5

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Date:	Fri, 24 Sep 2010 14:30:09 -0700
From:	Vernon Mauery <vernux@...ibm.com>
To:	Randy Dunlap <rdunlap@...otime.net>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Keith Mannthey <kmannth@...ibm.com>
Subject: Re: [RFC][Patch] IBM Real-Time "SMI Free" mode driver -v5

On 24-Sep-2010 02:20 PM, Randy Dunlap wrote:
>On Fri, 24 Sep 2010 14:06:42 -0700 Vernon Mauery wrote:
>
>> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
>> index cff7cc2..5fba368 100644
>> --- a/drivers/platform/x86/Kconfig
>> +++ b/drivers/platform/x86/Kconfig
>> @@ -590,4 +590,20 @@ config INTEL_IPS
>>  	  functionality.  If in doubt, say Y here; it will only load on
>>  	  supported platforms.
>>
>> +config IBM_RTL
>> +	tristate "Device driver to enable PRTL support"
>> +	depends on X86 && PCI
>> +	---help---
>> +	  Enable support for IBM Premium Real Time Mode (PRTM).
>> +	  This module will allow you the enter and exit PRTM in the BIOS via
>> +	  sysfs on platforms that support this feature.  System in PRTM will
>> +	  not recive CPU-generated SMIs for recoverable errors.  Use of this
>
>	      receive (again/still)

Ack. Again.

>> +	  feature without proper support may void your hardware warranty.
>> +
>> +	  If the proper BIOS support is found the driver will load and create
>> +	  /sys/devices/system/ibm_rtl/.  The "state" variable will indicate
>> +	  whether or not the BIOS is in PRTM.
[snip]
>> +#include <linux/delay.h>
>> +#include <linux/module.h>
>> +#include <linux/io.h>
>> +#include <linux/sysdev.h>
>> +#include <linux/dmi.h>
>> +#include <linux/mutex.h>
>> +#include <asm/bios_ebda.h>
>> +
>> +static int force;
>
>s/int/bool/
>
>> +module_param(force, bool, 0);
>> +MODULE_PARM_DESC(force, "Force driver load, ignore DMI data");
>> +
>> +static int debug;
>
>s/int/bool/

Ack.

>> +module_param(debug, bool, 0644);
>> +MODULE_PARM_DESC(debug, "Show debug output");
>> +
>> +MODULE_LICENSE("GPL");
>> +MODULE_AUTHOR("Keith Mannthey <kmmanth@...ibm.com>");
>> +MODULE_AUTHOR("Vernon Mauery <vernux@...ibm.com>");
>> +
>> +#define RTL_ADDR_TYPE_IO    1
>> +#define RTL_ADDR_TYPE_MMIO  2
>> +
>> +#define RTL_CMD_ENTER_PRTM  1
>> +#define RTL_CMD_EXIT_PRTM   2
>> +
>> +/* The RTL table as presented by the EBDA: */
>> +struct ibm_rtl_table {
>> +	char signature[5];
>
>Question:  are all 5 bytes of signature[] used?  It looks like the search code
>only checks for 32 bits of signature (and the last byte can be garbage?).

Technically, the 5 bytes are supposed to be "_RTL_", but it is a lot 
easier to just check _RTL since we can do that with a single read.  I 
suppose I could do a 64-bit read and mask the bits that matter.  Do you 
have an opinion on the matter?

>> +	u8 version;
>> +	u8 rt_status;
>> +	u8 command;
>> +	u8 command_status;
>> +	u8 cmd_address_type;
>> +	u8 cmd_granularity;
>> +	u8 cmd_offset;
>> +	u16 reserve1;
>> +	u32 cmd_port_address; /* platform dependent address */
>> +	u32 cmd_port_value;   /* platform dependent value */
>> +} __attribute__((packed));
>> +
>> +#define RTL_SIGNATURE (('L'<<24)|('T'<<16)|('R'<<8)|'_')
>> +
>> +#define RTL_DEBUG(A, ...) do { \
>> +	if (debug) \
>> +		pr_info("ibm-rtl: " A, ##__VA_ARGS__ ); \
>> +} while (0)
>> +
>> +static DEFINE_MUTEX(rtl_lock);
>> +static struct ibm_rtl_table __iomem *rtl_table;
>> +static void __iomem *ebda_map;
>> +static void __iomem *rtl_cmd_addr;
>> +static u8 rtl_cmd_type;
>> +static u8 rtl_cmd_width;
>
>...
>
>> +static int __init ibm_rtl_init(void) {
>> +	unsigned long ebda_addr, ebda_size;
>> +	unsigned int ebda_kb;
>> +	int ret = -ENODEV, i;
>> +
>> +	if (force)
>> +		pr_warning("ibm-rtl: module loaded by force!\n");
>
>Please drop the '!'.

Ack.

--Vernon
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