Subject: Re: [PATCH v4 04/11] VAS: Define vas_init() and vas_exit()

From: Tyrel Datwyler <[email-masked]>
Date: Mon, 24 Apr 2017 13:32:43 -0700

On 03/30/2017 10:13 PM, Sukadev Bhattiprolu wrote:
> Implement vas_init() and vas_exit() functions for a new VAS module.
> This VAS module is essentially a library for other device drivers
> and kernel users of the NX coprocessors like NX-842 and NX-GZIP.
> In the future this will be extended to add support for user space
> to access the NX coprocessors.
> 
> Signed-off-by: Sukadev Bhattiprolu <[email-masked]>
> ---
> Changelog[v4]:
> 	- [Michael Neuling] Fix some accidental deletions; fix help text
> 	  in Kconfig; change vas_initialized to a function; move from
> 	  drivers/misc to arch/powerpc/kernel
> 	- Drop the vas_window_reset() interface. It is not needed as
> 	  window will be initialized before each use.
> Changelog[v3]:
> 	- Zero vas_instances memory on allocation
> 	- [Haren Myneni] Fix description in Kconfig
> Changelog[v2]:
> 	- Get HVWC, UWC and window address parameters from device tree.
> ---
>  arch/powerpc/platforms/powernv/Kconfig      |  14 +++
>  arch/powerpc/platforms/powernv/Makefile     |   1 +
>  arch/powerpc/platforms/powernv/vas-window.c |  19 ++++
>  arch/powerpc/platforms/powernv/vas.c        | 145 ++++++++++++++++++++++++++++
>  arch/powerpc/platforms/powernv/vas.h        |   3 +
>  5 files changed, 182 insertions(+)
>  create mode 100644 arch/powerpc/platforms/powernv/vas-window.c
>  create mode 100644 arch/powerpc/platforms/powernv/vas.c
> 
> diff --git a/arch/powerpc/platforms/powernv/Kconfig b/arch/powerpc/platforms/powernv/Kconfig
> index 3a07e4d..54e2a4e 100644
> --- a/arch/powerpc/platforms/powernv/Kconfig
> +++ b/arch/powerpc/platforms/powernv/Kconfig
> @@ -27,3 +27,17 @@ config OPAL_PRD
>  	help
>  	  This enables the opal-prd driver, a facility to run processor
>  	  recovery diagnostics on OpenPower machines
> +
> +config VAS
> +	tristate "IBM Virtual Accelerator Switchboard (VAS)"
> +	depends on PPC_POWERNV
> +	default n
> +	help
> +	  This enables support for IBM Virtual Accelerator Switchboard (VAS).
> +
> +	  VAS allows accelerators in co-processors like NX-GZIP and NX-842
> +	  to be accessible to kernel subsystems.
> +
> +	  VAS adapters are found in POWER9 based systems.
> +
> +	  If unsure, say N.
> diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
> index b5d98cb..ebef20b 100644
> --- a/arch/powerpc/platforms/powernv/Makefile
> +++ b/arch/powerpc/platforms/powernv/Makefile
> @@ -12,3 +12,4 @@ obj-$(CONFIG_PPC_SCOM)	+= opal-xscom.o
>  obj-$(CONFIG_MEMORY_FAILURE)	+= opal-memory-errors.o
>  obj-$(CONFIG_TRACEPOINTS)	+= opal-tracepoints.o
>  obj-$(CONFIG_OPAL_PRD)	+= opal-prd.o
> +obj-$(CONFIG_VAS)	+= vas.o vas-window.o
> diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c
> new file mode 100644
> index 0000000..6156fbe
> --- /dev/null
> +++ b/arch/powerpc/platforms/powernv/vas-window.c
> @@ -0,0 +1,19 @@
> +/*
> + * Copyright 2016 IBM Corp.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <linux/types.h>
> +#include <linux/mutex.h>
> +
> +#include "vas.h"
> +
> +/* stub for now */
> +int vas_win_close(struct vas_window *window)
> +{
> +	return -1;
> +}
> diff --git a/arch/powerpc/platforms/powernv/vas.c b/arch/powerpc/platforms/powernv/vas.c
> new file mode 100644
> index 0000000..9bf8f57
> --- /dev/null
> +++ b/arch/powerpc/platforms/powernv/vas.c
> @@ -0,0 +1,145 @@
> +/*
> + * Copyright 2016 IBM Corp.
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version
> + * 2 of the License, or (at your option) any later version.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/export.h>
> +#include <linux/types.h>
> +#include <linux/slab.h>
> +#include <linux/of.h>
> +
> +#include "vas.h"
> +
> +static bool init_done;
> +int vas_num_instances;
> +struct vas_instance *vas_instances;
> +
> +static int init_vas_instance(struct device_node *dn,
> +				struct vas_instance *vinst)
> +{
> +	int rc;
> +	const __be32 *p;
> +	u64 values[6];
> +
> +	ida_init(&vinst->ida);
> +	mutex_init(&vinst->mutex);
> +
> +	p = of_get_property(dn, "vas-id", NULL);
> +	if (!p) {
> +		pr_err("VAS: NULL vas-id? %p\n", p);
> +		return -ENODEV;
> +	}
> +
> +	vinst->vas_id = of_read_number(p, 1);
> +
> +	/*
> +	 * Hardcoded 6 is tied to corresponding code in
> +	 *      skiboot.git/core/vas.c
> +	 */
> +	rc = of_property_read_variable_u64_array(dn, "reg", values, 6, 6);
> +	if (rc != 6) {
> +		pr_err("VAS %d: Unable to read reg properties, rc %d\n",
> +				vinst->vas_id, rc);
> +		return rc;
> +	}
> +
> +	vinst->hvwc_bar_start = values[0];
> +	vinst->hvwc_bar_len = values[1];
> +	vinst->uwc_bar_start = values[2];
> +	vinst->uwc_bar_len = values[3];
> +	vinst->win_base_addr = values[4];
> +	vinst->win_id_shift = values[5];
> +
> +	return 0;
> +}
> +
> +/*
> + * Although this is read/used multiple times, it is written to only
> + * during initialization.
> + */
> +struct vas_instance *find_vas_instance(int vasid)
> +{
> +	int i;
> +	struct vas_instance *vinst;
> +
> +	for (i = 0; i < vas_num_instances; i++) {
> +		vinst = &vas_instances[i];
> +		if (vinst->vas_id == vasid)
> +			return vinst;
> +	}
> +	pr_err("VAS instance for vas-id %d not found\n", vasid);
> +	WARN_ON_ONCE(1);
> +	return NULL;
> +}
> +
> +
> +bool vas_initialized(void)
> +{
> +	return init_done;
> +}
> +
> +int vas_init(void)
> +{
> +	int rc;
> +	struct device_node *dn;
> +	struct vas_instance *vinst;
> +
> +	if (!pvr_version_is(PVR_POWER9))
> +		return -ENODEV;
> +
> +	vas_num_instances = 0;
> +	for_each_node_by_name(dn, "vas")
> +		vas_num_instances++;
> +
> +	if (!vas_num_instances)
> +		return -ENODEV;
> +
> +	vas_instances = kcalloc(vas_num_instances, sizeof(*vinst), GFP_KERNEL);
> +	if (!vas_instances)
> +		return -ENOMEM;
> +
> +	vinst = &vas_instances[0];
> +	for_each_node_by_name(dn, "vas") {
> +		rc = init_vas_instance(dn, vinst);
> +		if (rc) {
> +			pr_err("Error %d initializing VAS instance %ld\n", rc,
> +					(vinst-&vas_instances[0]));

You need a of_node_put(dn) here. The for_each_node_by_name() loop will get/put the
references of the device_node for you. However, if you bail out of the loop you are
responsible for the of_node_put() on the current *dn reference otherwise you will leak a
reference.

-Tyrel

> +			goto cleanup;
> +		}
> +		vinst++;
> +	}
> +
> +	rc = -ENODEV;
> +	if (vinst == &vas_instances[0]) {
> +		/* Should not happen as we saw some above. */
> +		pr_err("VAS: Did not find any VAS DT nodes now!\n");
> +		goto cleanup;
> +	}
> +
> +	pr_devel("VAS: Initialized %d instances\n", vas_num_instances);
> +	init_done = true;
> +
> +	return 0;
> +
> +cleanup:
> +	kfree(vas_instances);
> +	return rc;
> +}
> +
> +void vas_exit(void)
> +{
> +	init_done = false;
> +	kfree(vas_instances);
> +}
> +
> +module_init(vas_init);
> +module_exit(vas_exit);
> +MODULE_DESCRIPTION("IBM Virtual Accelerator Switchboard");
> +MODULE_AUTHOR("Sukadev Bhattiprolu <[email-masked]>");
> +MODULE_LICENSE("GPL");
> diff --git a/arch/powerpc/platforms/powernv/vas.h b/arch/powerpc/platforms/powernv/vas.h
> index c63395d..46aaa17 100644
> --- a/arch/powerpc/platforms/powernv/vas.h
> +++ b/arch/powerpc/platforms/powernv/vas.h
> @@ -384,4 +384,7 @@ struct vas_winctx {
>  	enum vas_notify_after_count notify_after_count;
>  };
> 
> +extern bool vas_initialized(void);
> +extern struct vas_instance *find_vas_instance(int vasid);
> +
>  #endif /* _VAS_H */
>