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Date: Tue, 27 Jul 2021 08:47:47 +0200
From: Takashi Iwai <tiwai@...e.de>
To: Vitaly Rodionov <vitalyr@...nsource.cirrus.com>
Cc: Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
<alsa-devel@...a-project.org>, <patches@...nsource.cirrus.com>,
<linux-kernel@...r.kernel.org>,
Lucas Tanure <tanureal@...nsource.cirrus.com>
Subject: Re: [PATCH 13/27] ALSA: hda/cs8409: Dont disable I2C clock between consecutive accesses
On Mon, 26 Jul 2021 19:46:26 +0200,
Vitaly Rodionov wrote:
>
> From: Lucas Tanure <tanureal@...nsource.cirrus.com>
>
> Only disable I2C clock 25 ms after not being used
This is error-prone and might be racy, I'm afraid.
e.g. the offloaded work isn't canceled when unbinding the driver, so
it'll lead to a use-after-free. And the work doesn't take a mutex so
it may conflict with re-enabling side.
Above all, there is no description "why" this has to be done so.
Is it about the performance, or any other reason?
thanks,
Takashi
>
> Signed-off-by: Lucas Tanure <tanureal@...nsource.cirrus.com>
> Signed-off-by: Vitaly Rodionov <vitalyr@...nsource.cirrus.com>
> ---
> sound/pci/hda/patch_cs8409.c | 42 +++++++++++++++++++++++-------------
> sound/pci/hda/patch_cs8409.h | 4 ++++
> 2 files changed, 31 insertions(+), 15 deletions(-)
>
> diff --git a/sound/pci/hda/patch_cs8409.c b/sound/pci/hda/patch_cs8409.c
> index 08205c19698c..335bcdc69106 100644
> --- a/sound/pci/hda/patch_cs8409.c
> +++ b/sound/pci/hda/patch_cs8409.c
> @@ -53,6 +53,7 @@ static struct cs8409_spec *cs8409_alloc_spec(struct hda_codec *codec)
> if (!spec)
> return NULL;
> codec->spec = spec;
> + spec->codec = codec;
> codec->power_save_node = 1;
> snd_hda_gen_spec_init(&spec->gen);
>
> @@ -72,21 +73,34 @@ static inline void cs8409_vendor_coef_set(struct hda_codec *codec, unsigned int
> snd_hda_codec_write(codec, CS8409_PIN_VENDOR_WIDGET, 0, AC_VERB_SET_PROC_COEF, coef);
> }
>
> -/**
> +/*
> + * cs8409_disable_i2c_clock - Worker that disable the I2C Clock after 25ms without use
> + */
> +static void cs8409_disable_i2c_clock(struct work_struct *work)
> +{
> + struct cs8409_spec *spec = container_of(work, struct cs8409_spec, i2c_clk_work.work);
> +
> + cs8409_vendor_coef_set(spec->codec, 0x0,
> + cs8409_vendor_coef_get(spec->codec, 0x0) & 0xfffffff7);
> + spec->i2c_clck_enabled = 0;
> +}
> +
> +/*
> * cs8409_enable_i2c_clock - Enable I2C clocks
> * @codec: the codec instance
> - * @enable: Enable or disable I2C clocks
> - *
> * Enable or Disable I2C clocks.
> */
> -static void cs8409_enable_i2c_clock(struct hda_codec *codec, unsigned int enable)
> +static void cs8409_enable_i2c_clock(struct hda_codec *codec)
> {
> - unsigned int retval;
> - unsigned int newval;
> + struct cs8409_spec *spec = codec->spec;
> +
> + cancel_delayed_work_sync(&spec->i2c_clk_work);
>
> - retval = cs8409_vendor_coef_get(codec, 0x0);
> - newval = (enable) ? (retval | 0x8) : (retval & 0xfffffff7);
> - cs8409_vendor_coef_set(codec, 0x0, newval);
> + if (!spec->i2c_clck_enabled) {
> + cs8409_vendor_coef_set(codec, 0x0, cs8409_vendor_coef_get(codec, 0x0) | 0x8);
> + spec->i2c_clck_enabled = 1;
> + }
> + queue_delayed_work(system_power_efficient_wq, &spec->i2c_clk_work, msecs_to_jiffies(25));
> }
>
> /**
> @@ -134,7 +148,7 @@ static int cs8409_i2c_read(struct hda_codec *codec, unsigned int i2c_address, un
> if (spec->cs42l42_suspended)
> return -EPERM;
>
> - cs8409_enable_i2c_clock(codec, 1);
> + cs8409_enable_i2c_clock(codec);
> cs8409_vendor_coef_set(codec, CS8409_I2C_ADDR, i2c_address);
>
> if (paged) {
> @@ -157,8 +171,6 @@ static int cs8409_i2c_read(struct hda_codec *codec, unsigned int i2c_address, un
> /* Register in bits 15-8 and the data in 7-0 */
> read_data = cs8409_vendor_coef_get(codec, CS8409_I2C_QREAD);
>
> - cs8409_enable_i2c_clock(codec, 0);
> -
> return read_data & 0x0ff;
> }
>
> @@ -182,7 +194,7 @@ static int cs8409_i2c_write(struct hda_codec *codec, unsigned int i2c_address, u
> if (spec->cs42l42_suspended)
> return -EPERM;
>
> - cs8409_enable_i2c_clock(codec, 1);
> + cs8409_enable_i2c_clock(codec);
> cs8409_vendor_coef_set(codec, CS8409_I2C_ADDR, i2c_address);
>
> if (paged) {
> @@ -203,8 +215,6 @@ static int cs8409_i2c_write(struct hda_codec *codec, unsigned int i2c_address, u
> return -EIO;
> }
>
> - cs8409_enable_i2c_clock(codec, 0);
> -
> return 0;
> }
>
> @@ -705,6 +715,8 @@ void cs8409_cs42l42_fixups(struct hda_codec *codec, const struct hda_fixup *fix,
> spec->cs42l42_mic_jack_in = 0;
> spec->cs42l42_suspended = 1;
>
> + INIT_DELAYED_WORK(&spec->i2c_clk_work, cs8409_disable_i2c_clock);
> +
> /* Basic initial sequence for specific hw configuration */
> snd_hda_sequence_write(codec, cs8409_cs42l42_init_verbs);
>
> diff --git a/sound/pci/hda/patch_cs8409.h b/sound/pci/hda/patch_cs8409.h
> index bf0e8a4cc4cc..542582c213d2 100644
> --- a/sound/pci/hda/patch_cs8409.h
> +++ b/sound/pci/hda/patch_cs8409.h
> @@ -11,6 +11,7 @@
>
> #include <linux/pci.h>
> #include <sound/tlv.h>
> +#include <linux/workqueue.h>
> #include <sound/hda_codec.h>
> #include "hda_local.h"
> #include "hda_auto_parser.h"
> @@ -267,6 +268,7 @@ struct cs8409_cir_param {
>
> struct cs8409_spec {
> struct hda_gen_spec gen;
> + struct hda_codec *codec;
>
> unsigned int gpio_mask;
> unsigned int gpio_dir;
> @@ -278,6 +280,8 @@ struct cs8409_spec {
> s8 vol[CS42L42_VOLUMES];
>
> struct mutex cs8409_i2c_mux;
> + unsigned int i2c_clck_enabled;
> + struct delayed_work i2c_clk_work;
>
> /* verb exec op override */
> int (*exec_verb)(struct hdac_device *dev, unsigned int cmd, unsigned int flags,
> --
> 2.25.1
>
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