From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0b-0031df01.pphosted.com (mx0b-0031df01.pphosted.com [205.220.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 82F4631D381 for ; Mon, 23 Mar 2026 21:35:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.180.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774301723; cv=none; b=TNT7rvoYeWrjgV45lkviEdSZdFffumqpwcYhyLp9jxQ+G46qgUCScqkB/QlFkA8VSsZvMXOy+Ky6Q866yTsZUKsaH2BxO/cKHUkm2cLOAdQcOQDyMa4H176w2YKliI27TgIB05/8QwowZNEIQ/t7zyNHqi3uYVp6SiuPUeag/TY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774301723; c=relaxed/simple; bh=y205nGMlD28XUi3tF7Iw2shM585QNWZAz96/XwO9Phg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=W2IgrurhPrwDtLfK/nv0t86EPKOgo24Mffwe29sviTCRZDbq2MMklUqcvrwTqgaYjf8fICxCXNUktYS4sGfECFhuZ8OZdSsRjINrxMlJN/PnzOqhLsBFEzCYl/4gaxUr5RfUVbg2pbh4bF+gpBYc0w7XaYUxYGrBwJLQltZpja0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oss.qualcomm.com; spf=pass smtp.mailfrom=oss.qualcomm.com; dkim=pass (2048-bit key) header.d=qualcomm.com header.i=@qualcomm.com header.b=Bq6DwCOg; dkim=pass (2048-bit key) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.b=irZV47E8; arc=none smtp.client-ip=205.220.180.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=oss.qualcomm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=qualcomm.com header.i=@qualcomm.com header.b="Bq6DwCOg"; dkim=pass (2048-bit key) header.d=oss.qualcomm.com header.i=@oss.qualcomm.com header.b="irZV47E8" Received: from pps.filterd (m0279871.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.18.1.11/8.18.1.11) with ESMTP id 62NHqi4u3171141 for ; Mon, 23 Mar 2026 21:35:21 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=qualcomm.com; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=qcppdkim1; bh= 7wZB04XDAtb432QUhNE0MOhOE2cxeMMxeHACISlfOOE=; b=Bq6DwCOgyBqZox/0 HsOiBthrxLit9vTiND2MuSZoNnUvjAHc8+aBb16Dlpun5O821ZfzuQ4sUxbr9GEW GTHL+kDBVF9eIzLtzfHKHJAhcxFuvbujn1cGa6f0WC9In41oFyhilAJbuWe0Se1J DRtIoULA3h4Q56BO27VUyn8bWoeaCfl30oWc3/ySHkIJOVt5vKyD4VcMkqVi+csG nppNK56jVfbhf8CfuLU2DYY75wtkIiFVXy/yJ2kaw5JjpKe4hLaKKyD6H/Ov01Ih lJTfo4LZ/lXmdsiU4fF6HzVNLbuQnOavyJmqblnf+XV1lJPelUXsAHxsee2CBR3+ r3/z7g== Received: from mail-pl1-f200.google.com (mail-pl1-f200.google.com [209.85.214.200]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 4d35r21sn5-1 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NOT) for ; Mon, 23 Mar 2026 21:35:21 +0000 (GMT) Received: by mail-pl1-f200.google.com with SMTP id d9443c01a7336-2adef9d486bso29300275ad.2 for ; Mon, 23 Mar 2026 14:35:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oss.qualcomm.com; s=google; t=1774301720; x=1774906520; darn=vger.kernel.org; h=content-transfer-encoding:in-reply-to:content-language:from :references:cc:to:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=7wZB04XDAtb432QUhNE0MOhOE2cxeMMxeHACISlfOOE=; b=irZV47E8shs3qjdP2udxEcJu8KKiD27AMYrF0+mMUYq4DX6X2sAmjnvNayM38l0h7E jfvopgQSit3lG9fX0vyLkcpR9VGPMI8HvNhhhyGYQDfCpQ1ij87BGp7WUZVhD5hlkIYv 7E1k4kW6RzS77dscyizHU6pFEOUHoa7tae5As2KY2Qgu2bQ6rAQv3NmISoWcMAx9SWnO zKw7AdjKUWwiY2cuyr6whb4E741UIuwmQaQ7cnfbaoWhRXvOMum4+Pfe1k6OxMujyklO 0F+UQNTV3/UaQ7o+hJN+FHKvv7rPgHhVBc7rhCgbA0XHtEiCg4Sp1SGHId2YkS0wFykQ wc3Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1774301720; x=1774906520; h=content-transfer-encoding:in-reply-to:content-language:from :references:cc:to:subject:user-agent:mime-version:date:message-id :x-gm-gg:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=7wZB04XDAtb432QUhNE0MOhOE2cxeMMxeHACISlfOOE=; b=aCSqtOVlBKgIhF4RDreRmfcLDpHMyOvKx9BhOGbne0OK5SagrOsyh1YhSgsEQxEyKC ApbwsU8qoXfshJVReV2VjA3x2kth/h8JunnOQGiEjPvraSQxrKnGWNPiu07dQzc/lXnK FVgI1S/Yljsrw2hlKg+MdYnjh9fYOz9SzQ8MbWXs0p+IbUXLxOHGGaCRM+9287O97ZJk oozsuQpSWDrhrRqUYyTTeEYRJCASWkRSWj3KHSUW8e0TUHs1bV66p3Ei/ghStwMnaAnl sA0Xw86TX0DprXXI7xLHOcUkGh2YWClmHAi78KeYZi7dufFxEH8eWgYvM4fWjzWOO8zo byIA== X-Forwarded-Encrypted: i=1; AJvYcCUFSbyw8jH2XG6Mfjw7nJxrnIjMEzhyPZvs1HNJ9Sylv7Zsyaj8PuAE8C3qFCydyO6eG+Ym7YY/tKH7U0Uk@vger.kernel.org X-Gm-Message-State: AOJu0YzeMupdNThmaV/RYlRoc+m/RvUWdq23cBC5dPc3GkoE2qU+2jc/ oi2ZB7eVxzpra57tJtyjTDgEmm1yVR0Ssit6vBuRjatXUDRSlbKpMpIrUQ+70MlW4p0Nbgd9iEb 0Qjq3znkuiomiaPBcJKM02ZI53NulQfP6Jirx+Ub5059dJnqrp3AGsMn5/NS31qbNEY/M X-Gm-Gg: ATEYQzyhMmZBITaYVo970Zi76mHgU3JmbsFvPEKWRWzyJljpUMJu7U+4s/c0Kwjo0l6 70Xk7LsuP6doPx4XGqmVffr34P0bfsuA2aC4e8rvhzlJW1/6myZ/cPsskcSCIMhs/yf7kCGbV9g eoRedaoL/letuJfOP8d+efHMeRep3AMx58bV6f7jXeUvRbHV/F0JP1JVoPlfOHl2g5WY7F+USAS T2WeRkpWggxRtN8WEX5tmt0man1kBZdrIyxeIeA5ptRNxe4FllO7JXLmLvis0XgX4K351MB3WF2 Q6lrF1ZAdM3HZqE5D34f5Z7V3GXbfhp9wt2i8x4YueI1iYsM9CIaoxjOzUQoWZtUYGvvBkzrEYW UWmmZyyixbycH6YODB3sbIO41S0SBQCcFce5m5AMCl1wV920= X-Received: by 2002:a17:902:e5c9:b0:2b0:5626:f75d with SMTP id d9443c01a7336-2b0827a4f48mr121650265ad.26.1774301720347; Mon, 23 Mar 2026 14:35:20 -0700 (PDT) X-Received: by 2002:a17:902:e5c9:b0:2b0:5626:f75d with SMTP id d9443c01a7336-2b0827a4f48mr121650025ad.26.1774301719880; Mon, 23 Mar 2026 14:35:19 -0700 (PDT) Received: from [192.168.1.12] ([106.222.230.237]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b08353e94asm119327655ad.25.2026.03.23.14.35.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 23 Mar 2026 14:35:19 -0700 (PDT) Message-ID: <697b9e3d-3af9-4d39-8d99-bb8b1e5a9c19@oss.qualcomm.com> Date: Tue, 24 Mar 2026 03:05:12 +0530 Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 06/16] drm/msm/a6xx: Use barriers while updating HFI Q headers To: rob.clark@oss.qualcomm.com Cc: Sean Paul , Konrad Dybcio , Dmitry Baryshkov , Abhinav Kumar , Jessica Zhang , Marijn Suijten , David Airlie , Simona Vetter , Antonino Maniscalco , Connor Abbott , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , linux-arm-msm@vger.kernel.org, dri-devel@lists.freedesktop.org, freedreno@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20260324-a8xx-gpu-batch2-v1-0-fc95b8d9c017@oss.qualcomm.com> <20260324-a8xx-gpu-batch2-v1-6-fc95b8d9c017@oss.qualcomm.com> From: Akhil P Oommen Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Authority-Analysis: v=2.4 cv=VvUuwu2n c=1 sm=1 tr=0 ts=69c1b219 cx=c_pps a=IZJwPbhc+fLeJZngyXXI0A==:117 a=WRfdsTvTEh9BIu3+I5rxZw==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=3WHJM1ZQz_JShphwDgj5:22 a=EUspDBNiAAAA:8 a=d0dIk93vvDk8Ins0EvIA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=uG9DUKGECoFWVXl0Dc02:22 X-Proofpoint-GUID: pYlDRBY2NRpOJBfJITMF7-vdLsITRbLE X-Proofpoint-ORIG-GUID: pYlDRBY2NRpOJBfJITMF7-vdLsITRbLE X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzIzMDE2MCBTYWx0ZWRfX9k+2NTNwiW0Q X7gvhf9mjl0D+GOoneZZW4L+Psn12yW2vq2gJmD6J0jWZtiJuVpU7pzcPNay/pGSeLU+aWW8uol wmz7cuk3ljWzjazfFQ/ErsFsTXia9zP6eU6O0L4l/n8IcOwEsakvvVYqhSRf2RgQbCmyz93vrp0 +EDOP3h4KoBXujAnt2dFf9yDRmqrCv0MF4u8yCgQw1ojry8SXFfzXm9A5IC4HXvH0gypFOgSsj0 krTr+rMFIeX9h/8D6sXtLTDj8omEkF/A6/S2RP3zo7xPsXyFY+qyApZD1vngJTPXVsGLPmfbwa7 Z2vjv7M8w61nrOuUTd+XR1n4VpmbQHTJwJnnG2z9gmR3EnTy5aP4NnYDscE3siK3Q4iGDlVgxIM KYqPrpAfaEPiyIx47KrpKwtTvFXwj5YKft+ut+j4ihnuGKkod4QHUAcr8E0DcvY14VuDZoC8ONW bafGTDM44GzxCVNieDg== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-23_05,2026-03-23_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 malwarescore=0 spamscore=0 adultscore=0 lowpriorityscore=0 impostorscore=0 bulkscore=0 clxscore=1015 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603230160 On 3/24/2026 2:15 AM, Rob Clark wrote: > On Mon, Mar 23, 2026 at 1:13 PM Akhil P Oommen wrote: >> >> To avoid harmful compiler optimizations and IO reordering in the HW, use >> barriers and READ/WRITE_ONCE helpers as necessary while accessing the HFI >> queue index variables. > > This feels a bit like it should have Fixes: ? Ack. Will update in v2. -Akhil > >> Signed-off-by: Akhil P Oommen >> --- >> drivers/gpu/drm/msm/adreno/a6xx_hfi.c | 14 ++++++++++---- >> 1 file changed, 10 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c >> index 2daaa340366d..aef00c2dd137 100644 >> --- a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c >> +++ b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c >> @@ -34,7 +34,7 @@ static int a6xx_hfi_queue_read(struct a6xx_gmu *gmu, >> struct a6xx_hfi_queue_header *header = queue->header; >> u32 i, hdr, index = header->read_index; >> >> - if (header->read_index == header->write_index) { >> + if (header->read_index == READ_ONCE(header->write_index)) { >> header->rx_request = 1; >> return 0; >> } >> @@ -62,7 +62,10 @@ static int a6xx_hfi_queue_read(struct a6xx_gmu *gmu, >> if (!gmu->legacy) >> index = ALIGN(index, 4) % header->size; >> >> - header->read_index = index; >> + /* Ensure all memory operations are complete before updating the read index */ >> + dma_mb(); >> + >> + WRITE_ONCE(header->read_index, index); >> return HFI_HEADER_SIZE(hdr); >> } >> >> @@ -74,7 +77,7 @@ static int a6xx_hfi_queue_write(struct a6xx_gmu *gmu, >> >> spin_lock(&queue->lock); >> >> - space = CIRC_SPACE(header->write_index, header->read_index, >> + space = CIRC_SPACE(header->write_index, READ_ONCE(header->read_index), >> header->size); >> if (space < dwords) { >> header->dropped++; >> @@ -95,7 +98,10 @@ static int a6xx_hfi_queue_write(struct a6xx_gmu *gmu, >> queue->data[index] = 0xfafafafa; >> } >> >> - header->write_index = index; >> + /* Ensure all memory operations are complete before updating the write index */ >> + dma_mb(); >> + >> + WRITE_ONCE(header->write_index, index); >> spin_unlock(&queue->lock); >> >> gmu_write(gmu, REG_A6XX_GMU_HOST2GMU_INTR_SET, 0x01); >> >> -- >> 2.51.0 >>