linux-kernel - Re: [PATCH v5 2/4] media: ov5675: add device-tree support and support runtime PM

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Message-ID: <249907c9-1d59-d8ab-1870-c01e8ace7d18@theobroma-systems.com>
Date:   Tue, 7 Jun 2022 16:08:39 +0200
From:   Quentin Schulz <quentin.schulz@...obroma-systems.com>
To:     Jacopo Mondi <jacopo@...ndi.org>,
        Quentin Schulz <foss+kernel@...il.net>
Cc:     shawnx.tu@...el.com, mchehab@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/4] media: ov5675: add device-tree support and support
 runtime PM

Hi Jacopo,

On 5/31/22 15:16, Jacopo Mondi wrote:
> Hi Quentin,
>     one more question
> 
> On Wed, May 25, 2022 at 04:58:31PM +0200, Quentin Schulz wrote:
>> From: Quentin Schulz <quentin.schulz@...obroma-systems.com>
>>
>> Until now, this driver only supported ACPI. This adds support for
>> Device Tree too while enabling clock and regulators in runtime PM.
>>
>> Signed-off-by: Quentin Schulz <quentin.schulz@...obroma-systems.com>
>> ---
>>
>> v5:
>>   - fixed -Wdeclaration-after-statement for delay_us,
>>
>> v4:
>>   - added delays based on clock cycles as specified in datasheet for
>>   pre-power-off and post-power-on,
>>   - re-arranged clk handling, shutdown toggling and regulator handling to
>>   better match power up/down sequence defined in datasheet,
>>   - added comment on need for regulator being stable before releasing
>>   shutdown pin,
>>
>> v3:
>>   - added linux/mod_devicetable.h include,
>>   - moved delay for reset pulse right after the regulators are enabled,
>>   - removed check on is_acpi_node in favor of checks on presence of OF
>>   properties (e.g. devm_clk_get_optional returns NULL),
>>   - moved power management out of system suspend/resume into runtime PM
>>   callbacks,
>>   - removed ACPI specific comment since it's not specific to this driver,
>>   - changed devm_clk_get to devm_clk_get_optional,
>>   - remove OF use of clock-frequency (handled by devm_clk_get_optional
>>   directly),
>>   - removed name of clock (only one, so no need for anything explicit)
>>   when requesting a clock from OF,
>>   - wrapped lines to 80 chars,
>>
>> v2:
>>   - fixed unused-const-variable warning by removing of_match_ptr in
>>   of_match_table, reported by kernel test robot,
>>
>>   drivers/media/i2c/ov5675.c | 149 +++++++++++++++++++++++++++++++------
>>   1 file changed, 128 insertions(+), 21 deletions(-)
>>
>> diff --git a/drivers/media/i2c/ov5675.c b/drivers/media/i2c/ov5675.c
>> index 82ba9f56baec8..ea801edb8e408 100644
>> --- a/drivers/media/i2c/ov5675.c
>> +++ b/drivers/media/i2c/ov5675.c
>> @@ -3,10 +3,14 @@
>>
>>   #include <asm/unaligned.h>
>>   #include <linux/acpi.h>
>> +#include <linux/clk.h>
>>   #include <linux/delay.h>
>> +#include <linux/gpio/consumer.h>
>>   #include <linux/i2c.h>
>> +#include <linux/mod_devicetable.h>
>>   #include <linux/module.h>
>>   #include <linux/pm_runtime.h>
>> +#include <linux/regulator/consumer.h>
>>   #include <media/v4l2-ctrls.h>
>>   #include <media/v4l2-device.h>
>>   #include <media/v4l2-fwnode.h>
>> @@ -17,7 +21,7 @@
>>
>>   #define OV5675_LINK_FREQ_450MHZ		450000000ULL
>>   #define OV5675_SCLK			90000000LL
>> -#define OV5675_MCLK			19200000
>> +#define OV5675_XVCLK_19_2		19200000
>>   #define OV5675_DATA_LANES		2
>>   #define OV5675_RGB_DEPTH		10
>>
>> @@ -76,6 +80,14 @@
>>
>>   #define to_ov5675(_sd)			container_of(_sd, struct ov5675, sd)
>>
>> +static const char * const ov5675_supply_names[] = {
>> +	"avdd",		/* Analog power */
>> +	"dovdd",	/* Digital I/O power */
>> +	"dvdd",		/* Digital core power */
>> +};
>> +
>> +#define OV5675_NUM_SUPPLIES	ARRAY_SIZE(ov5675_supply_names)
>> +
>>   enum {
>>   	OV5675_LINK_FREQ_900MBPS,
>>   };
>> @@ -484,6 +496,9 @@ struct ov5675 {
>>   	struct v4l2_subdev sd;
>>   	struct media_pad pad;
>>   	struct v4l2_ctrl_handler ctrl_handler;
>> +	struct clk		*xvclk;
>> +	struct gpio_desc	*reset_gpio;
>> +	struct regulator_bulk_data supplies[OV5675_NUM_SUPPLIES];
>>
>>   	/* V4L2 Controls */
>>   	struct v4l2_ctrl *link_freq;
>> @@ -944,6 +959,56 @@ static int ov5675_set_stream(struct v4l2_subdev *sd, int enable)
>>   	return ret;
>>   }
>>
>> +static int ov5675_power_off(struct device *dev)
> 
> Does this (and power_on) require __maybe_unused to avoid a warning
> when compiling without CONFIG_PM support ? Have you tried that ?
> 

It does not, because they are called manually in the probe function and 
its error path (but thanks for the heads up, because I definitely forgot 
about this one).

I received some review outside of this mailing list telling me the error 
path is incorrect for pm_runtime so I'll have a look at it before 
sending a v6.

Cheers,
Quentin