linux-kernel - Re: [PATCH] extcon: extcon-axp288: use low level P-Unit semaphore lock for axp288 register accesses

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Date:   Thu, 9 Sep 2021 18:20:49 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Fabio Aiuto <fabioaiuto83@...il.com>,
        Chanwoo Choi <cw00.choi@...sung.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] extcon: extcon-axp288: use low level P-Unit semaphore
 lock for axp288 register accesses

Hi All,

On 9/9/21 5:18 PM, Fabio Aiuto wrote:
> use low level P-Unit semaphore lock for axp288 register
> accesses directly and for more than one access a time,
> to reduce the number of times this semaphore is locked
> and released which is an expensive operation.
> 
> i2c-bus to the XPower is shared between the kernel and the
> SoCs P-Unit. The P-Unit has a semaphore wich the kernel must
> lock for axp288 register accesses. When the P-Unit semaphore
> is locked CPU and GPU power states cannot change or the system
> will freeze.
> 
> The P-Unit semaphore lock is already managed inside the regmap
> access logic, but for each access the semaphore is locked and
> released. So use directly iosf_mbi_(un)block_punit_i2c_access(),
> we are safe in doing so because nested calls to the same
> semaphore are turned to nops.
> 
> Suggested-by: Hans de Goede <hdegoede@...hat.com>
> Signed-off-by: Fabio Aiuto <fabioaiuto83@...il.com>

Thanks, patch looks good to me:

Reviewed-by: Hans de Goede <hdegoede@...hat.com>

I've also given it a test run on a Chuwi Hibook which uses this PMIC:

Tested-by: Hans de Goede <hdegoede@...hat.com>

Regards,

Hans




> ---
>  drivers/extcon/extcon-axp288.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/extcon/extcon-axp288.c b/drivers/extcon/extcon-axp288.c
> index fdb31954cf2b..460402b14ef2 100644
> --- a/drivers/extcon/extcon-axp288.c
> +++ b/drivers/extcon/extcon-axp288.c
> @@ -24,6 +24,7 @@
>  
>  #include <asm/cpu_device_id.h>
>  #include <asm/intel-family.h>
> +#include <asm/iosf_mbi.h>
>  
>  /* Power source status register */
>  #define PS_STAT_VBUS_TRIGGER		BIT(0)
> @@ -215,6 +216,8 @@ static int axp288_handle_chrg_det_event(struct axp288_extcon_info *info)
>  	unsigned int cable = info->previous_cable;
>  	bool vbus_attach = false;
>  
> +	iosf_mbi_block_punit_i2c_access();
> +
>  	vbus_attach = axp288_get_vbus_attach(info);
>  	if (!vbus_attach)
>  		goto no_vbus;
> @@ -253,6 +256,8 @@ static int axp288_handle_chrg_det_event(struct axp288_extcon_info *info)
>  	}
>  
>  no_vbus:
> +	iosf_mbi_unblock_punit_i2c_access();
> +
>  	extcon_set_state_sync(info->edev, info->previous_cable, false);
>  	if (info->previous_cable == EXTCON_CHG_USB_SDP)
>  		extcon_set_state_sync(info->edev, EXTCON_USB, false);
> @@ -275,6 +280,8 @@ static int axp288_handle_chrg_det_event(struct axp288_extcon_info *info)
>  	return 0;
>  
>  dev_det_ret:
> +	iosf_mbi_unblock_punit_i2c_access();
> +
>  	if (ret < 0)
>  		dev_err(info->dev, "failed to detect BC Mod\n");
>  
> @@ -307,11 +314,14 @@ static irqreturn_t axp288_extcon_isr(int irq, void *data)
>  
>  static void axp288_extcon_enable(struct axp288_extcon_info *info)
>  {
> +	iosf_mbi_block_punit_i2c_access();
>  	regmap_update_bits(info->regmap, AXP288_BC_GLOBAL_REG,
>  						BC_GLOBAL_RUN, 0);
>  	/* Enable the charger detection logic */
>  	regmap_update_bits(info->regmap, AXP288_BC_GLOBAL_REG,
>  					BC_GLOBAL_RUN, BC_GLOBAL_RUN);
> +
> +	iosf_mbi_unblock_punit_i2c_access();
>  }
>  
>  static void axp288_put_role_sw(void *data)
> @@ -384,10 +394,14 @@ static int axp288_extcon_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> +	iosf_mbi_block_punit_i2c_access();
> +
>  	info->vbus_attach = axp288_get_vbus_attach(info);
>  
>  	axp288_extcon_log_rsi(info);
>  
> +	iosf_mbi_unblock_punit_i2c_access();
> +
>  	/* Initialize extcon device */
>  	info->edev = devm_extcon_dev_allocate(&pdev->dev,
>  					      axp288_extcon_cables);
>