[PATCH v4 2/2] powerpc/powernv: Add ultravisor message log interface

[Claudio Carvalho]

On 8/28/19 10:05 AM, Michael Ellerman wrote:
> From: Claudio Carvalho <cclaudio at linux.ibm.com>
>
> The ultravisor (UV) provides an in-memory console which follows the
> OPAL in-memory console structure.
>
> This patch extends the OPAL msglog code to initialize the UV memory
> console and provide the "/sys/firmware/ultravisor/msglog" interface
> for userspace to view the UV message log.

Tested-by: Claudio Carvalho <cclaudio at linux.ibm.com>

Thanks,
Claudio

>
> Signed-off-by: Claudio Carvalho <cclaudio at linux.ibm.com>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
> ---
> v4: mpe: Move all the code into ultravisor.c.
>     Consistently use "uv_" as the prefix not "ultra_".
>     Use powernv.h for routines that are shared within the platform.
>     Rather than bloating the kernel with strings for every rare error
>     case, return error codes from the init routine which can be
>     seen with initcall_debug.
> ---
>  arch/powerpc/platforms/powernv/powernv.h    |  5 +++
>  arch/powerpc/platforms/powernv/ultravisor.c | 45 +++++++++++++++++++++
>  2 files changed, 50 insertions(+)
>
> diff --git a/arch/powerpc/platforms/powernv/powernv.h b/arch/powerpc/platforms/powernv/powernv.h
> index fd4a1c5a6369..1aa51c4fa904 100644
> --- a/arch/powerpc/platforms/powernv/powernv.h
> +++ b/arch/powerpc/platforms/powernv/powernv.h
> @@ -30,4 +30,9 @@ extern void opal_event_shutdown(void);
>  
>  bool cpu_core_split_required(void);
>  
> +struct memcons;
> +ssize_t memcons_copy(struct memcons *mc, char *to, loff_t pos, size_t count);
> +u32 memcons_get_size(struct memcons *mc);
> +struct memcons *memcons_init(struct device_node *node, const char *mc_prop_name);
> +
>  #endif /* _POWERNV_H */
> diff --git a/arch/powerpc/platforms/powernv/ultravisor.c b/arch/powerpc/platforms/powernv/ultravisor.c
> index 02ac57b4bded..e4a00ad06f9d 100644
> --- a/arch/powerpc/platforms/powernv/ultravisor.c
> +++ b/arch/powerpc/platforms/powernv/ultravisor.c
> @@ -8,9 +8,15 @@
>  #include <linux/init.h>
>  #include <linux/printk.h>
>  #include <linux/of_fdt.h>
> +#include <linux/of.h>
>  
>  #include <asm/ultravisor.h>
>  #include <asm/firmware.h>
> +#include <asm/machdep.h>
> +
> +#include "powernv.h"
> +
> +static struct kobject *ultravisor_kobj;
>  
>  int __init early_init_dt_scan_ultravisor(unsigned long node, const char *uname,
>  					 int depth, void *data)
> @@ -22,3 +28,42 @@ int __init early_init_dt_scan_ultravisor(unsigned long node, const char *uname,
>  	pr_debug("Ultravisor detected!\n");
>  	return 1;
>  }
> +
> +static struct memcons *uv_memcons;
> +
> +static ssize_t uv_msglog_read(struct file *file, struct kobject *kobj,
> +			      struct bin_attribute *bin_attr, char *to,
> +			      loff_t pos, size_t count)
> +{
> +	return memcons_copy(uv_memcons, to, pos, count);
> +}
> +
> +static struct bin_attribute uv_msglog_attr = {
> +	.attr = {.name = "msglog", .mode = 0400},
> +	.read = uv_msglog_read
> +};
> +
> +static int __init uv_init(void)
> +{
> +	struct device_node *node;
> +
> +	if (!firmware_has_feature(FW_FEATURE_ULTRAVISOR))
> +		return 0;
> +
> +	node = of_find_compatible_node(NULL, NULL, "ibm,uv-firmware");
> +	if (!node)
> +		return -ENODEV;
> +
> +	uv_memcons = memcons_init(node, "memcons");
> +	if (!uv_memcons)
> +		return -ENOENT;
> +
> +	uv_msglog_attr.size = memcons_get_size(uv_memcons);
> +
> +	ultravisor_kobj = kobject_create_and_add("ultravisor", firmware_kobj);
> +	if (!ultravisor_kobj)
> +		return -ENOMEM;
> +
> +	return sysfs_create_bin_file(ultravisor_kobj, &uv_msglog_attr);
> +}
> +machine_subsys_initcall(powernv, uv_init);