linux-kernel - Re: [PATCH 1/2] leds: flash: leds-qcom-flash: update torch current clamp setting

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Message-ID: <f4f46e92-3d49-4bcf-a23e-223c758f56e9@oss.qualcomm.com>
Date: Mon, 28 Jul 2025 10:27:07 +0800
From: Fenglin Wu <fenglin.wu@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>, kernel@....qualcomm.com,
        Lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>,
        Fenglin Wu <quic_fenglinw@...cinc.com>
Cc: Subbaraman Narayanamurthy <subbaraman.narayanamurthy@....qualcomm.com>,
        linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] leds: flash: leds-qcom-flash: update torch current
 clamp setting


On 7/25/2025 8:37 PM, Konrad Dybcio wrote:
> On 7/25/25 12:04 PM, 'Fenglin Wu via B4 Relay' via kernel wrote:
>> From: Fenglin Wu <fenglin.wu@....qualcomm.com>
>>
>> There is a register to clamp the flash current per LED channel when
>> safety timer is disabled. It needs to be updated according to the
>> maximum torch LED current setting to ensure the torch current won't
>> be clamped unexpectedly.
>>
>> Fixes: 96a2e242a5dc ("leds: flash: Add driver to support flash LED module in QCOM PMICs")
>> Signed-off-by: Fenglin Wu <fenglin.wu@....qualcomm.com>
>> ---
>>   drivers/leds/flash/leds-qcom-flash.c | 16 +++++++++++++---
>>   1 file changed, 13 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/leds/flash/leds-qcom-flash.c b/drivers/leds/flash/leds-qcom-flash.c
>> index 89cf5120f5d55bbb7e24faa8c3a946416f8fed46..9c2e41cfddcf2d50d5a633cb157084371a631d74 100644
>> --- a/drivers/leds/flash/leds-qcom-flash.c
>> +++ b/drivers/leds/flash/leds-qcom-flash.c
>> @@ -1,6 +1,6 @@
>>   // SPDX-License-Identifier: GPL-2.0-only
>>   /*
>> - * Copyright (c) 2022, 2024 Qualcomm Innovation Center, Inc. All rights reserved.
>> + * Copyright (c) 2022, 2024-2025 Qualcomm Innovation Center, Inc. All rights reserved.
>>    */
>>   
>>   #include <linux/bitfield.h>
>> @@ -111,6 +111,7 @@ enum {
>>   	REG_IRESOLUTION,
>>   	REG_CHAN_STROBE,
>>   	REG_CHAN_EN,
>> +	REG_TORCH_CLAMP,
> This is not the name of this register on at least PM8150L
The register is referred to as 'TIMER_DISA_MITIGATION_CLAMP' in the 
documentation. 'TIMER_DISA' indicates the flash module operating in 
torch mode. We can remove 'MITIGATION' to create a shorter name for the 
enum.
>
>>   	REG_THERM_THRSH1,
>>   	REG_THERM_THRSH2,
>>   	REG_THERM_THRSH3,
>> @@ -127,6 +128,7 @@ static const struct reg_field mvflash_3ch_regs[REG_MAX_COUNT] = {
>>   	REG_FIELD(0x47, 0, 5),                  /* iresolution	*/
>>   	REG_FIELD_ID(0x49, 0, 2, 3, 1),         /* chan_strobe	*/
>>   	REG_FIELD(0x4c, 0, 2),                  /* chan_en	*/
>> +	REG_FIELD(0xec, 0, 6),			/* torch_clamp	*/
> Please keep it sorted by address
I need to keep the 'therm_thrsh1/2/3' register fields at the end of this 
array because 'mvflash_4ch_regs' doesn't include a 'therm_thrsh3' 
register. Placing the 'therm_thrshx' registers in the middle would 
require creating a placeholder, which I couldn't figure out how to do 
effectively. Do you have any suggestions?
>
>
>>   	REG_FIELD(0x56, 0, 2),			/* therm_thrsh1 */
>>   	REG_FIELD(0x57, 0, 2),			/* therm_thrsh2 */
>>   	REG_FIELD(0x58, 0, 2),			/* therm_thrsh3 */
>> @@ -142,6 +144,7 @@ static const struct reg_field mvflash_4ch_regs[REG_MAX_COUNT] = {
>>   	REG_FIELD(0x49, 0, 3),			/* iresolution	*/
>>   	REG_FIELD_ID(0x4a, 0, 6, 4, 1),		/* chan_strobe	*/
>>   	REG_FIELD(0x4e, 0, 3),			/* chan_en	*/
>> +	REG_FIELD(0xed, 0, 6),			/* torch_clamp	*/
>>   	REG_FIELD(0x7a, 0, 2),			/* therm_thrsh1 */
>>   	REG_FIELD(0x78, 0, 2),			/* therm_thrsh2 */
>>   };
>> @@ -156,6 +159,7 @@ struct qcom_flash_data {
>>   	u8			max_channels;
>>   	u8			chan_en_bits;
>>   	u8			revision;
>> +	u8			torch_clamp;
>>   };
>>   
>>   struct qcom_flash_led {
>> @@ -702,6 +706,7 @@ static int qcom_flash_register_led_device(struct device *dev,
>>   	u32 current_ua, timeout_us;
>>   	u32 channels[4];
>>   	int i, rc, count;
>> +	u8 torch_clamp;
>>   
>>   	count = fwnode_property_count_u32(node, "led-sources");
>>   	if (count <= 0) {
>> @@ -751,6 +756,12 @@ static int qcom_flash_register_led_device(struct device *dev,
>>   	current_ua = min_t(u32, current_ua, TORCH_CURRENT_MAX_UA * led->chan_count);
>>   	led->max_torch_current_ma = current_ua / UA_PER_MA;
>>   
>> +	torch_clamp = (current_ua / led->chan_count) / TORCH_IRES_UA;
>> +	if (torch_clamp != 0)
>> +		torch_clamp--;
> In case anyone's wondering, ((1<<6) + 1) 4 * 5000 == 1280000 which we set
> on some (all?) devices
>
> Konrad