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Mon, 21 Sep 2026 02:29:06 -0700 (PDT) X-Received: by 2002:a05:6214:76d:b0:90c:e7f4:8bfe with SMTP id 6a1803df08f44-9129c780e3cmr115801736d6.2.1789982946186; Mon, 21 Sep 2026 02:29:06 -0700 (PDT) Received: from [192.168.202.12] ([178.235.128.140]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-6aa67e11071sm3867362a12.23.2026.09.21.02.29.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Sep 2026 02:29:05 -0700 (PDT) Message-ID: Date: Mon, 21 Sep 2026 11:29:03 +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 Subject: Re: [PATCH v3 2/4] backlight: qcom-wled: Fix WLED3 brightness register stride To: david@ixit.cz, Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller , Kiran Gunda , Marco Mattiolo , =?UTF-8?B?QmFybmFiw6FzIEN6w6ltw6Fu?= Cc: linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, phone-devel@vger.kernel.org, Joel Selvaraj , stable@vger.kernel.org References: <20260914-qcom-wled-backlight-v3-0-d69fe9843841@ixit.cz> <20260914-qcom-wled-backlight-v3-2-d69fe9843841@ixit.cz> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <20260914-qcom-wled-backlight-v3-2-d69fe9843841@ixit.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIxMDEzNiBTYWx0ZWRfX0v+Got7VcXQk K46aFBzPCE8MCcVfAry/yFlQ8cfD0fUcYW2ThVSyZxr3Y4Lg7sM1CeZ1ie1ncisaGzd/PrkPZeg TsZhO/F9HZUYaV4XMzWvRq0SrFjEPmDuRE4HO0XN1F6aEb80Etr+yYVzb3pqzsFTt+RGBwj81Ze o45LEwoWc7mJX5bC3W4ODIfKS7pRFZx2D0tV0qSzfPdmF6cASc50yF5CfoqddDekZF4xktitE+C vAjCaoL0EmBwRgsWJn8oUGP0gZo8ye7byKL0Hu6chFLoO2qnSDQ/Jp9sJG5rKQ5wHzxg6/c+K0n /u30XPySqbNan2+qoIO32hOzvNg8Yfk4IRufgY677/0KhghQ1tEJCT9BSpFgJCWsauXGz20Wlqf sy78ZJ1CmFgk/CqX3RTh+XJAJiyQ4zOjauTb6mJxenOF5xM96TNUB9u4ctfVlTRzSPeKLvtv2BX MNHMAE7NLrrGnNz6McA== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIxMDEzNiBTYWx0ZWRfX5BC55TZOTu12 4Iy+I2x2wTG/XE3c3g76ShlwnxEnd9ZLQYZvih5b0z3cYn7GVNhwB2SGlai8iUzjMybCKH1TfHJ JMNeXV0ZuodM4o5dgaAHWf1Je+swEyQ= X-Proofpoint-ORIG-GUID: ONRiGNvtrgFf4-t9Cd11xjxwQhNCIua- X-Proofpoint-GUID: ONRiGNvtrgFf4-t9Cd11xjxwQhNCIua- X-Authority-Analysis: v=2.4 cv=W7etxhWk c=1 sm=1 tr=0 ts=6ab0f8e3 cx=c_pps a=JbAStetqSzwMeJznSMzCyw==:117 a=PRfkaYvzSr8QmIIGAkY2Sg==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=3WHJM1ZQz_JShphwDgj5:22 a=VwQbUJbxAAAA:8 a=fY3HbpO4PgkFXDM8leYA:9 a=QEXdDO2ut3YA:10 a=uxP6HrT_eTzRwkO_Te1X:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-09-21_03,2026-09-16_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 spamscore=0 malwarescore=0 suspectscore=0 bulkscore=0 impostorscore=0 priorityscore=1501 phishscore=0 lowpriorityscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609210136 On 9/14/26 8:14 PM, David Heidelberg via B4 Relay wrote: > From: David Heidelberg > > WLED3 has a 16-bit brightness register pair per string, at 0x40 + 2*n, > which is what the pm8941-wled driver wrote to: > > rc = regmap_bulk_write(wled->regmap, > wled->addr + WLED3_CTRL_REG_VAL_BASE + 2 * i, > v, 2); > > The restructuring for WLED3 turned that into WLED3_SINK_REG_BRIGHT(n), > defined as 0x40 + n, so the two byte writes for consecutive strings > overlap: string 1 overwrites the MSB of string 0 with its own LSB, and > with the default three strings only string 1 ends up with the requested > value. > > Use the 2 byte stride. > > Fixes: 775d2ffb4af6 ("backlight: qcom-wled: Restructure the driver for WLED3") > Cc: stable@vger.kernel.org > Assisted-by: LLM > Signed-off-by: David Heidelberg > --- > drivers/video/backlight/qcom-wled.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/video/backlight/qcom-wled.c b/drivers/video/backlight/qcom-wled.c > index a76158a298335..e1962c2d90ed4 100644 > --- a/drivers/video/backlight/qcom-wled.c > +++ b/drivers/video/backlight/qcom-wled.c > @@ -54,17 +54,17 @@ > #define WLED3_SINK_REG_SYNC 0x47 > #define WLED3_SINK_REG_SYNC_CLEAR 0x00 > > #define WLED3_SINK_REG_CURR_SINK 0x4f > #define WLED3_SINK_REG_CURR_SINK_MASK GENMASK(7, 5) > #define WLED3_SINK_REG_CURR_SINK_SHFT 5 > > /* WLED3 specific per-'string' registers below */ > -#define WLED3_SINK_REG_BRIGHT(n) (0x40 + n) > +#define WLED3_SINK_REG_BRIGHT(n) (0x40 + (n * 0x10)) You said 2 in the commit message and you set it to 2 in patch 4 Konrad