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([2a01:e0a:106d:1080:b6d0:a628:be51:f552]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45ef354b5bdsm3169110f8f.21.2026.05.29.05.50.43 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 29 May 2026 05:50:43 -0700 (PDT) Message-ID: <4001cf6a-b7de-4933-96bc-c9b4ccb53e4d@linaro.org> Date: Fri, 29 May 2026 14:50:43 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Neil Armstrong Reply-To: Neil Armstrong Subject: Re: [PATCH v3 1/2] dt-bindings: leds: backlight: document the SY7758 6-channel High Efficiency LED Driver To: Daniel Thompson Cc: Lee Jones , Jingoo Han , Pavel Machek , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Helge Deller , dri-devel@lists.freedesktop.org, linux-leds@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fbdev@vger.kernel.org, KancyJoe , Krzysztof Kozlowski References: <20260519-topic-sm8650-ayaneo-pocket-s2-sy7758-v3-0-ec8194bbc885@linaro.org> <20260519-topic-sm8650-ayaneo-pocket-s2-sy7758-v3-1-ec8194bbc885@linaro.org> Content-Language: en-US, fr Autocrypt: addr=neil.armstrong@linaro.org; keydata= xsBNBE1ZBs8BCAD78xVLsXPwV/2qQx2FaO/7mhWL0Qodw8UcQJnkrWmgTFRobtTWxuRx8WWP GTjuhvbleoQ5Cxjr+v+1ARGCH46MxFP5DwauzPekwJUD5QKZlaw/bURTLmS2id5wWi3lqVH4 BVF2WzvGyyeV1o4RTCYDnZ9VLLylJ9bneEaIs/7cjCEbipGGFlfIML3sfqnIvMAxIMZrvcl9 qPV2k+KQ7q+aXavU5W+yLNn7QtXUB530Zlk/d2ETgzQ5FLYYnUDAaRl+8JUTjc0CNOTpCeik 80TZcE6f8M76Xa6yU8VcNko94Ck7iB4vj70q76P/J7kt98hklrr85/3NU3oti3nrIHmHABEB AAHNKk5laWwgQXJtc3Ryb25nIDxuZWlsLmFybXN0cm9uZ0BsaW5hcm8ub3JnPsLAkQQTAQoA OwIbIwULCQgHAwUVCgkICwUWAgMBAAIeAQIXgBYhBInsPQWERiF0UPIoSBaat7Gkz/iuBQJk Q5wSAhkBAAoJEBaat7Gkz/iuyhMIANiD94qDtUTJRfEW6GwXmtKWwl/mvqQtaTtZID2dos04 YqBbshiJbejgVJjy+HODcNUIKBB3PSLaln4ltdsV73SBcwUNdzebfKspAQunCM22Mn6FBIxQ GizsMLcP/0FX4en9NaKGfK6ZdKK6kN1GR9YffMJd2P08EO8mHowmSRe/ExAODhAs9W7XXExw UNCY4pVJyRPpEhv373vvff60bHxc1k/FF9WaPscMt7hlkbFLUs85kHtQAmr8pV5Hy9ezsSRa GzJmiVclkPc2BY592IGBXRDQ38urXeM4nfhhvqA50b/nAEXc6FzqgXqDkEIwR66/Gbp0t3+r yQzpKRyQif3OwE0ETVkGzwEIALyKDN/OGURaHBVzwjgYq+ZtifvekdrSNl8TIDH8g1xicBYp QTbPn6bbSZbdvfeQPNCcD4/EhXZuhQXMcoJsQQQnO4vwVULmPGgtGf8PVc7dxKOeta+qUh6+ SRh3vIcAUFHDT3f/Zdspz+e2E0hPV2hiSvICLk11qO6cyJE13zeNFoeY3ggrKY+IzbFomIZY 4yG6xI99NIPEVE9lNBXBKIlewIyVlkOaYvJWSV+p5gdJXOvScNN1epm5YHmf9aE2ZjnqZGoM Mtsyw18YoX9BqMFInxqYQQ3j/HpVgTSvmo5ea5qQDDUaCsaTf8UeDcwYOtgI8iL4oHcsGtUX oUk33HEAEQEAAcLAXwQYAQIACQUCTVkGzwIbDAAKCRAWmrexpM/4rrXiB/sGbkQ6itMrAIfn M7IbRuiSZS1unlySUVYu3SD6YBYnNi3G5EpbwfBNuT3H8//rVvtOFK4OD8cRYkxXRQmTvqa3 3eDIHu/zr1HMKErm+2SD6PO9umRef8V82o2oaCLvf4WeIssFjwB0b6a12opuRP7yo3E3gTCS KmbUuLv1CtxKQF+fUV1cVaTPMyT25Od+RC1K+iOR0F54oUJvJeq7fUzbn/KdlhA8XPGzwGRy 4zcsPWvwnXgfe5tk680fEKZVwOZKIEuJC3v+/yZpQzDvGYJvbyix0lHnrCzq43WefRHI5XTT QbM0WUIBIcGmq38+OgUsMYu4NzLu7uZFAcmp6h8g Organization: Linaro In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 5/29/26 12:35, Daniel Thompson wrote: > On Fri, May 29, 2026 at 12:16:07PM +0200, Neil Armstrong wrote: >> On 5/29/26 12:07, Daniel Thompson wrote: >>> On Tue, May 19, 2026 at 10:43:38AM +0200, Neil Armstrong wrote: >>>> Document the Silergy SY7758 6-channel High Efficiency LED Driver >>>> used for backlight brightness control. >>>> >>>> Reviewed-by: Krzysztof Kozlowski >>>> Signed-off-by: Neil Armstrong >>>> --- >>>> .../bindings/leds/backlight/silergy,sy7758.yaml | 53 ++++++++++++++++++++++ >>>> 1 file changed, 53 insertions(+) >>>> >>>> diff --git a/Documentation/devicetree/bindings/leds/backlight/silergy,sy7758.yaml b/Documentation/devicetree/bindings/leds/backlight/silergy,sy7758.yaml >>>> new file mode 100644 >>>> index 000000000000..80e978d691c2 >>>> --- /dev/null >>>> +++ b/Documentation/devicetree/bindings/leds/backlight/silergy,sy7758.yaml >>>> @@ -0,0 +1,53 @@ >>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) >>>> +%YAML 1.2 >>>> +--- >>>> +$id: http://devicetree.org/schemas/leds/backlight/silergy,sy7758.yaml# >>>> +$schema: http://devicetree.org/meta-schemas/core.yaml# >>>> + >>>> +title: Silergy SY7758 6-channel High Efficiency LED Driver >>>> + >>>> +maintainers: >>>> + - Neil Armstrong >>>> + >>>> +description: >>>> + Silergy SY7758 is a high efficiency 6-channels LED backlight >>>> + driver with I2C brightness control. >>>> + >>>> +allOf: >>>> + - $ref: common.yaml# >>>> + >>>> +properties: >>>> + compatible: >>>> + const: silergy,sy7758 >>>> + >>>> + reg: >>>> + maxItems: 1 >>>> + >>>> + vddio-supply: true >>>> + >>>> + enable-gpios: >>>> + maxItems: 1 >>>> + >>>> +required: >>>> + - compatible >>>> + - reg >>>> + - vddio-supply >>> >>> Sorry for missing this in v2 but is vddio-supply really a required >>> property? >>> >>> It's unusual for supplies to be mandatory (and the it is not mandatory >>> in the driver implementation). >> >> This device is a little bit special, the VDDIO regulator is used to provide >> power for the I/O via the enable input, so basically the enable gpio power >> level is provided by VDDIO. > > I don't follow. The EN pin acts as both VDDIO and as an enable but it's > still effectively a power rail isn't it (albeit one with very low current > draw). Here's the datasheet description: ``` Dual-purpose pin serving both as a chip enable and as a power supply reference for PWM, SDA, and SCL inputs. ``` The VDD input is directly provided by the panel, so Linux has no control of it so I haven't added it. > > It looked to me like the correct way to model to two power rails > going into the chip is vdd-supply (main power supply) and vddio-supply > (EN/VDDIO) I don't understand why a single pin needs both a regulator > *and* a GPIO in the DT bindings? I don't have a the schematics of the board, but as I understood one gpio is actually enabling an regulator which provides power to the IC (vddio) and a second gpio will either drive the EN signal to GND or VDDIO to provide a clean rising edge on the EN pin. So it's not really 2 regulators, and having regulators means the enable signal can be shared and would have regulator characteristics which it hasn't. > >> This is the recommended way from the datasheet, and I assume it will be used >> like that on other platforms (if it exists...) >> >> This is why it's mandatory and enabled first before setting the enable pin. > > It's not mandatory for the C implementation. devm_regulator_get_enable() > will provide a dummy regulator if the property is omitted. So yeah if you prefer I'll re-spin with the vddio regulator as optional because between both, the VDDIO is the only which could be shared with other devices or always-on. Neil > > > Daniel.