Subject: Re: [PATCH v6 02/11] powerpc/powernv: Autoload IMC device driver module

From: Stewart Smith <[email-masked]>
Date: Thu, 06 Apr 2017 17:04:13 +1000

Madhavan Srinivasan <[email-masked]> writes:
> From: Hemant Kumar <[email-masked]>
>
> This patch does three things :
>  - Enables "opal.c" to create a platform device for the IMC interface
>    according to the appropriate compatibility string.
>  - Find the reserved-memory region details from the system device tree
>    and get the base address of HOMER (Reserved memory) region address for each chip.
>  - We also get the Nest PMU counter data offsets (in the HOMER region)
>    and their sizes. The offsets for the counters' data are fixed and
>    won't change from chip to chip.
>
> The device tree parsing logic is separated from the PMU creation
> functions (which is done in subsequent patches).
>
> Signed-off-by: Anju T Sudhakar <[email-masked]>
> Signed-off-by: Hemant Kumar <[email-masked]>
> Signed-off-by: Madhavan Srinivasan <[email-masked]>
> ---
>  arch/powerpc/platforms/powernv/Makefile   |   2 +-
>  arch/powerpc/platforms/powernv/opal-imc.c | 126 ++++++++++++++++++++++++++++++
>  arch/powerpc/platforms/powernv/opal.c     |  14 ++++
>  3 files changed, 141 insertions(+), 1 deletion(-)
>  create mode 100644 arch/powerpc/platforms/powernv/opal-imc.c
>
> diff --git a/arch/powerpc/platforms/powernv/Makefile b/arch/powerpc/platforms/powernv/Makefile
> index b5d98cb3f482..44909fec1121 100644
> --- a/arch/powerpc/platforms/powernv/Makefile
> +++ b/arch/powerpc/platforms/powernv/Makefile
> @@ -2,7 +2,7 @@ obj-y			+= setup.o opal-wrappers.o opal.o opal-async.o idle.o
>  obj-y			+= opal-rtc.o opal-nvram.o opal-lpc.o opal-flash.o
>  obj-y			+= rng.o opal-elog.o opal-dump.o opal-sysparam.o opal-sensor.o
>  obj-y			+= opal-msglog.o opal-hmi.o opal-power.o opal-irqchip.o
> -obj-y			+= opal-kmsg.o
> +obj-y			+= opal-kmsg.o opal-imc.o
>
>  obj-$(CONFIG_SMP)	+= smp.o subcore.o subcore-asm.o
>  obj-$(CONFIG_PCI)	+= pci.o pci-ioda.o npu-dma.o
> diff --git a/arch/powerpc/platforms/powernv/opal-imc.c b/arch/powerpc/platforms/powernv/opal-imc.c
> new file mode 100644
> index 000000000000..c476d596c6a8
> --- /dev/null
> +++ b/arch/powerpc/platforms/powernv/opal-imc.c
> @@ -0,0 +1,126 @@
> +/*
> + * OPAL IMC interface detection driver
> + * Supported on POWERNV platform
> + *
> + * Copyright	(C) 2016 Madhavan Srinivasan, IBM Corporation.
> + *		(C) 2016 Hemant K Shaw, IBM Corporation.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/miscdevice.h>
> +#include <linux/fs.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_platform.h>
> +#include <linux/poll.h>
> +#include <linux/mm.h>
> +#include <linux/slab.h>
> +#include <linux/crash_dump.h>
> +#include <asm/opal.h>
> +#include <asm/io.h>
> +#include <asm/uaccess.h>
> +#include <asm/cputable.h>
> +#include <asm/imc-pmu.h>
> +
> +struct perchip_nest_info nest_perchip_info[IMC_MAX_CHIPS];
> +
> +static int opal_imc_counters_probe(struct platform_device *pdev)
> +{
> +	struct device_node *child, *imc_dev, *rm_node = NULL;
> +	struct perchip_nest_info *pcni;
> +	u32 pages, nest_offset, nest_size, idx;
> +	int i = 0;
> +	const char *node_name;
> +	const __be32 *addrp;
> +	u64 reg_addr, reg_size;
> +
> +	if (!pdev || !pdev->dev.of_node)
> +		return -ENODEV;
> +
> +	/*
> +	 * Check whether this kdump kernel. If yes, just return.
> +	 */
> +	if (is_kdump_kernel())
> +		return -ENODEV;
> +
> +	imc_dev = pdev->dev.of_node;
> +
> +	/*
> +	 * nest_offset : where the nest-counters' data start.
> +	 * size : size of the entire nest-counters region
> +	 */
> +	if (of_property_read_u32(imc_dev, "imc-nest-offset", &nest_offset))
> +		goto err;
> +
> +	if (of_property_read_u32(imc_dev, "imc-nest-size", &nest_size))
> +		goto err;
> +
> +	/* Find the "homer region" for each chip */
> +	rm_node = of_find_node_by_path("/reserved-memory");
> +	if (!rm_node)
> +		goto err;
> +
> +	for_each_child_of_node(rm_node, child) {
> +		if (of_property_read_string_index(child, "name", 0,
> +						  &node_name))
> +			continue;
> +		if (strncmp("ibm,homer-image", node_name,
> +			    strlen("ibm,homer-image")))
> +			continue;

A better way to do this would be to reference the memory region, like
what's shown in
Documentation/devicetree/bindings/reserved-memory/reserved-memory.txt

just reference the phandle of the memory region.

seeing as these are per chip, why not just have something linking
together chip-id and the IMC layout node?

-- 
Stewart Smith
OPAL Architect, IBM.