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Mon, 21 Sep 2026 04:08:45 -0700 (PDT) X-Received: by 2002:a05:622a:1911:b0:52d:8270:8e36 with SMTP id d75a77b69052e-532b743d863mr99485651cf.5.1789988925398; Mon, 21 Sep 2026 04:08:45 -0700 (PDT) Received: from [192.168.202.12] ([178.235.128.140]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-3a607468ee9sm22436471fa.3.2026.09.21.04.08.42 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 21 Sep 2026 04:08:44 -0700 (PDT) Message-ID: <22355625-a2ea-4b6e-99b3-65cf93ac8034@oss.qualcomm.com> Date: Mon, 21 Sep 2026 13:08:41 +0200 Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 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: <20260921-qcom-wled-backlight-v4-0-bab8c7ef73cb@ixit.cz> <20260921-qcom-wled-backlight-v4-2-bab8c7ef73cb@ixit.cz> Content-Language: en-US From: Konrad Dybcio In-Reply-To: <20260921-qcom-wled-backlight-v4-2-bab8c7ef73cb@ixit.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: ixzaJreJyJbszCGJaxcCiC6caf9jtQbX X-Proofpoint-ORIG-GUID: ixzaJreJyJbszCGJaxcCiC6caf9jtQbX X-Authority-Analysis: v=2.4 cv=OtraWC/t c=1 sm=1 tr=0 ts=6ab11040 cx=c_pps a=WeENfcodrlLV9YRTxbY/uA==:117 a=PRfkaYvzSr8QmIIGAkY2Sg==:17 a=IkcTkHD0fZMA:10 a=VdqzKS8jKosA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=_K5XuSEh1TEqbUxoQ0s3:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=Q3U7ue9uqBl2Npjrlm8A:9 a=QEXdDO2ut3YA:10 a=kacYvNCVWA4VmyqE58fU:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTIxMDE2MCBTYWx0ZWRfXy6Gl5YDMvZLL lCxC+WcDbxTXFuklIblSBdFh8SQ6HitRxE6la0hzR26cex3myv1TB7s1oKLTmwF2DqIqSlOTT4Z Fd10MYfl4i7CLYb+YUhwHOheA5vF6QmZP6+sAJtGUbd8P5FwyJL/NSbjgjkr8u84ZVP5Zuy3gz8 e3cHbHAg0xiDrpric73gXyVOy3vVKdpRKId/P16l7kJ/ItLgxZ57G3TgqyvmBmbXJVXYlWVyTha sjAFMDaSHoLfnSZY2RBRUL1kKBZRlUBPDqq3AS8mF8vr2LNOqOoRV3exNMdIk1ciX5CJjVqLssA qOoweXT3b5kTNxUusaXlsAgImDYvXgoVx6HbAfbHMyEmfEP/VZ2x6OwkzlGtFJqD27bBNwuoEsb OMpZfqJu19aAlwFpnxjVwXAlnRVtM68de+LYBAP+T5NawLA5catpC83xunTQ33wDu3f1akGwJ7x 541v0Vzkp6EW+4BwK5Q== X-Proofpoint-Spam-Info: AW1haW4tMjYwOTIxMDE2MCBTYWx0ZWRfX1ZeaM60bUPy2 0AEZxMclfnGtbRdicL3uk01+gy5Yq9KaLqp5kYDaIfPthW5aSO4QFn4QpYeGuln/MEcRQwdsF5L oPA/tSOLxXd50i1rJiegWpOF36BjB5M= 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_04,2026-09-16_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 spamscore=0 lowpriorityscore=0 bulkscore=0 suspectscore=0 malwarescore=0 adultscore=0 phishscore=0 clxscore=1015 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609210160 On 9/21/26 12:46 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 2281007bdd459..f452d328997ad 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 * 0x2)) Ideally n would be wrapped in its own parentheses (doesn't checkpatch warn against that?) Reviewed-by: Konrad Dybcio Konrad