Re: [PATCH v1] x86: punit_atom: punit device state debug driver

Ingo Molnar
2015-05-02T06:00:58Z

* Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> wrote:

> The patch adds a debug driver, which dumps the power states
> of all the North complex (NC) devices. This debug interface is
> useful to figure out the NC IPs which blocks the S0ix
> transitions on the platform. This is extremely useful during
> enabling PM on customer platforms and derivatives.

Looks useful.

> This submission not a complete rewrite from the original
> submission from Kumar P, Mahesh <mahesh.kumar.p.intel.com>.
> https://lkml.org/lkml/2014/11/5/367

This sentence does not parse. Did you mean 'is a complete rewrite'?

> +config PUNIT_ATOM_DEBUG
> + tristate "ATOM Punit debug driver"
> + depends on DEBUG_FS
> + select IOSF_MBI
> + ---help---
> + This is a debug driver, which gets the power states
> + of all Punit North Complex devices.The power states of
> + each IP is exposed as part of the debugfs interface.

What is an 'IP'?

Also:

s/devices.The
/devices. The

> +
> endmenu
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index cdb1b70..2ecbd55 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -110,6 +110,7 @@ obj-$(CONFIG_PERF_EVENTS) += perf_regs.o
> obj-$(CONFIG_TRACING) += tracepoint.o
> obj-$(CONFIG_IOSF_MBI) += iosf_mbi.o
> obj-$(CONFIG_PMC_ATOM) += pmc_atom.o
> +obj-$(CONFIG_PUNIT_ATOM_DEBUG) += punit_atom_debug.o
>
> ###
> # 64 bit specific files
> diff --git a/arch/x86/kernel/punit_atom_debug.c b/arch/x86/kernel/punit_atom_debug.c

Please put this somewhere suitable in arch/x86/platform/.

> +/*
> + * Intel SOC Punit device state debug driver
> + * Copyright (c) 2015, Intel Corporation.

Would be nice to add a blurb about what 'Intel SOC Punit' systems are.
There doesn't seem to be anything in the kernel source about it, so
you have a golden opportunity here.

> +#define PUNIT_PORT 0x04
> +#define PWRGT_STATUS 0x61 /* Power gate status reg */
> +#define VED_SS_PM0 0x32 /* Subsystem config/status Video */
> +#define ISP_SS_PM0 0x39 /* Subsystem config/status ISP */
> +#define MIO_SS_PM 0x3B /* Subsystem config/status MIO */
> +#define SSS_SHIFT 24
> +#define RENDER_POS 0
> +#define MEDIA_POS 2
> +#define VLV_DISPLAY_POS 6
> +#define CHT_DSP_SSS 0x36 /* Subsystem config/status DSP */
> +#define CHT_DSP_SSS_POS 16

All the magic constants need some explanation for humans, not just
some.

> +static const struct punit_device punit_device_byt[] = {
> + { "GFX RENDER", PWRGT_STATUS, RENDER_POS },
> + { "GFX MEDIA", PWRGT_STATUS, MEDIA_POS },
> + { "DISPLAY", PWRGT_STATUS, VLV_DISPLAY_POS },
> + { "VED", VED_SS_PM0, SSS_SHIFT},
> + { "ISP", ISP_SS_PM0, SSS_SHIFT},
> + { "MIO", MIO_SS_PM, SSS_SHIFT},
> + { NULL}
> +};
> +
> +static const struct punit_device punit_device_cht[] = {
> + { "GFX RENDER", PWRGT_STATUS, RENDER_POS },
> + { "GFX MEDIA", PWRGT_STATUS, MEDIA_POS },
> + { "DSP", CHT_DSP_SSS, CHT_DSP_SSS_POS },
> + { "VED", VED_SS_PM0, SSS_SHIFT},
> + { "ISP", ISP_SS_PM0, SSS_SHIFT},
> + { "MIO", MIO_SS_PM, SSS_SHIFT},
> + { NULL}
> +};

Please align such initialization tables vertically, like you did here:

> +static const struct file_operations punit_dev_state_ops = {
> + .open = punit_dev_state_open,
> + .read = seq_read,
> + .llseek = seq_lseek,
> + .release = single_release,
> +};

> + punit_dbg_file = debugfs_create_dir("punit_atom", NULL);
> + if (!punit_dbg_file)
> + return -ENXIO;
> +
> + dev_state = debugfs_create_file("dev_state", S_IFREG | S_IRUGO,
> + punit_dbg_file, NULL,
> + &punit_dev_state_ops);

So why isn't something that is declaradly a power state dump, called
"power_state" or "dev_power_state"?

> +MODULE_AUTHOR("Kumar P, Mahesh <mahesh.kumar.p.intel.com>");
> +MODULE_DESCRIPTION("Driver for Punit devices states debugging");
> +MODULE_LICENSE("GPL v2");

Btw., you can have multiple MODULE_AUTHOR() lines, so you can credit
yourself as well. Take a look at drivers/net/wireless/at76c50x-usb.c's
MODULE_AUTHOR() for grins.

Thanks,

Ingo