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Wed, 04 Sep 2024 20:46:11 +0000 (GMT) Received: from nalasex01b.na.qualcomm.com (nalasex01b.na.qualcomm.com [10.47.209.197]) by NALASPPMTA05.qualcomm.com (8.18.1.2/8.18.1.2) with ESMTPS id 484KkAwo026397 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 4 Sep 2024 20:46:10 GMT Received: from [10.81.25.230] (10.49.16.6) by nalasex01b.na.qualcomm.com (10.47.209.197) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Wed, 4 Sep 2024 13:46:10 -0700 Message-ID: <941d1bfb-965e-43e4-9f34-edaf2de5d661@quicinc.com> Date: Wed, 4 Sep 2024 13:46:09 -0700 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 3/4] PCI: qcom: Add equalization settings for 16.0 GT/s Content-Language: en-US To: Manivannan Sadhasivam , Johan Hovold CC: Richard Zhu , Lucas Stach , Lorenzo Pieralisi , =?UTF-8?Q?Krzysztof_Wilczy=C5=84ski?= , Rob Herring , Bjorn Helgaas , Shawn Guo , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Jingoo Han , Chuanhua Lei , Marek Vasut , Yoshihiro Shimoda , , , , , , , , References: <20240904-pci-qcom-gen4-stability-v6-0-ec39f7ae3f62@linaro.org> <20240904-pci-qcom-gen4-stability-v6-3-ec39f7ae3f62@linaro.org> <20240904155233.zm3m6x3wvco35g6t@thinkpad> From: Shashank Babu Chinta Venkata In-Reply-To: <20240904155233.zm3m6x3wvco35g6t@thinkpad> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.49.16.6] X-ClientProxiedBy: nalasex01a.na.qualcomm.com (10.47.209.196) To nalasex01b.na.qualcomm.com (10.47.209.197) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: yZ_tsvi8JzuRLAhD_yL9olgx968NN90N X-Proofpoint-GUID: yZ_tsvi8JzuRLAhD_yL9olgx968NN90N X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.60.29 definitions=2024-09-04_18,2024-09-04_01,2024-09-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 adultscore=0 bulkscore=0 mlxscore=0 impostorscore=0 suspectscore=0 phishscore=0 mlxlogscore=999 lowpriorityscore=0 spamscore=0 clxscore=1011 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2407110000 definitions=main-2409040157 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240904_134625_098140_3069D850 X-CRM114-Status: GOOD ( 17.46 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 9/4/24 08:52, Manivannan Sadhasivam wrote: > On Wed, Sep 04, 2024 at 11:39:09AM +0200, Johan Hovold wrote: >> On Wed, Sep 04, 2024 at 12:41:59PM +0530, Manivannan Sadhasivam via B4 Relay wrote: >>> From: Shashank Babu Chinta Venkata >>> >>> During high data transmission rates such as 16.0 GT/s, there is an >>> increased risk of signal loss due to poor channel quality and interference. >>> This can impact receiver's ability to capture signals accurately. Hence, >>> signal compensation is achieved through appropriate lane equalization >>> settings at both transmitter and receiver. This will result in increased >>> PCIe signal strength. >>> >>> Signed-off-by: Shashank Babu Chinta Venkata >>> Reviewed-by: Manivannan Sadhasivam >>> [mani: dropped the code refactoring and minor changes] >>> Signed-off-by: Manivannan Sadhasivam >> >>> +#define GEN3_EQ_CONTROL_OFF 0x8a8 >> >> Nit: uppercase hex since that's what is used for the other offsets >> >>> +#define GEN3_EQ_CONTROL_OFF_FB_MODE GENMASK(3, 0) >>> +#define GEN3_EQ_CONTROL_OFF_PHASE23_EXIT_MODE BIT(4) >>> +#define GEN3_EQ_CONTROL_OFF_PSET_REQ_VEC GENMASK(23, 8) >>> +#define GEN3_EQ_CONTROL_OFF_FOM_INC_INITIAL_EVAL BIT(24) >>> + >>> +#define GEN3_EQ_FB_MODE_DIR_CHANGE_OFF 0x8ac >> >> Nit: odd indentation uses spaces, uppercase >> >>> +#define GEN3_EQ_FMDC_T_MIN_PHASE23 GENMASK(4, 0) >>> +#define GEN3_EQ_FMDC_N_EVALS GENMASK(9, 5) >>> +#define GEN3_EQ_FMDC_MAX_PRE_CUSROR_DELTA GENMASK(13, 10) >>> +#define GEN3_EQ_FMDC_MAX_POST_CUSROR_DELTA GENMASK(17, 14) >>> + >>> #define PCIE_PORT_MULTI_LANE_CTRL 0x8C0 >>> #define PORT_MLTI_UPCFG_SUPPORT BIT(7) >>> >>> diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.c b/drivers/pci/controller/dwc/pcie-qcom-common.c >>> new file mode 100644 >>> index 000000000000..dc7d93db9dc5 >>> --- /dev/null >>> +++ b/drivers/pci/controller/dwc/pcie-qcom-common.c >>> @@ -0,0 +1,45 @@ >>> +// SPDX-License-Identifier: GPL-2.0 >>> +/* >>> + * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved. >>> + */ >>> + >>> +#include >>> + >>> +#include "pcie-designware.h" >>> +#include "pcie-qcom-common.h" >>> + >>> +void qcom_pcie_common_set_16gt_eq_settings(struct dw_pcie *pci) >>> +{ >>> + u32 reg; >>> + >>> + /* >>> + * GEN3_RELATED_OFF register is repurposed to apply equalization >>> + * settings at various data transmission rates through registers namely >>> + * GEN3_EQ_*. RATE_SHADOW_SEL bit field of GEN3_RELATED_OFF determines >>> + * data rate for which this equalization settings are applied. >> >> *The* RATE_SHADOW_SEL bit field >> >> *the* data rate >> >> s/this/these/ >> >>> + */ >>> + reg = dw_pcie_readl_dbi(pci, GEN3_RELATED_OFF); >>> + reg &= ~GEN3_RELATED_OFF_GEN3_ZRXDC_NONCOMPL; >>> + reg &= ~GEN3_RELATED_OFF_RATE_SHADOW_SEL_MASK; >>> + reg |= FIELD_PREP(GEN3_RELATED_OFF_RATE_SHADOW_SEL_MASK, 0x1); >> >> How does 0x1 map to gen4/16 GT? >> > > I need inputs from Shashank here as I don't know the answer. > > - Mani GEN3_RELATED_OFF has been repurposed to use with multiple data rates. RATE_SHADOW_SEL_MASK on GEN3_RELATED_OFF value decides the data rate of shadow registers namely GEN3_EQ_* registers. Per documentation 0x0 maps to 8 GT/s, 0x1 maps to 16 GT/s and 0x2 maps to 32 GT/s. > >>> + dw_pcie_writel_dbi(pci, GEN3_RELATED_OFF, reg); >>> + >>> + reg = dw_pcie_readl_dbi(pci, GEN3_EQ_FB_MODE_DIR_CHANGE_OFF); >>> + reg &= ~(GEN3_EQ_FMDC_T_MIN_PHASE23 | >>> + GEN3_EQ_FMDC_N_EVALS | >>> + GEN3_EQ_FMDC_MAX_PRE_CUSROR_DELTA | >>> + GEN3_EQ_FMDC_MAX_POST_CUSROR_DELTA); >>> + reg |= FIELD_PREP(GEN3_EQ_FMDC_T_MIN_PHASE23, 0x1) | >>> + FIELD_PREP(GEN3_EQ_FMDC_N_EVALS, 0xd) | >>> + FIELD_PREP(GEN3_EQ_FMDC_MAX_PRE_CUSROR_DELTA, 0x5) | >>> + FIELD_PREP(GEN3_EQ_FMDC_MAX_POST_CUSROR_DELTA, 0x5); >>> + dw_pcie_writel_dbi(pci, GEN3_EQ_FB_MODE_DIR_CHANGE_OFF, reg); >>> + >>> + reg = dw_pcie_readl_dbi(pci, GEN3_EQ_CONTROL_OFF); >>> + reg &= ~(GEN3_EQ_CONTROL_OFF_FB_MODE | >>> + GEN3_EQ_CONTROL_OFF_PHASE23_EXIT_MODE | >>> + GEN3_EQ_CONTROL_OFF_FOM_INC_INITIAL_EVAL | >>> + GEN3_EQ_CONTROL_OFF_PSET_REQ_VEC); >>> + dw_pcie_writel_dbi(pci, GEN3_EQ_CONTROL_OFF, reg); >>> +} >>> +EXPORT_SYMBOL_GPL(qcom_pcie_common_set_16gt_eq_settings); >>> diff --git a/drivers/pci/controller/dwc/pcie-qcom-common.h b/drivers/pci/controller/dwc/pcie-qcom-common.h >>> new file mode 100644 >>> index 000000000000..259e04b7bdf9 >>> --- /dev/null >>> +++ b/drivers/pci/controller/dwc/pcie-qcom-common.h >>> @@ -0,0 +1,8 @@ >>> +/* SPDX-License-Identifier: GPL-2.0 */ >>> +/* >>> + * Copyright (c) 2024 Qualcomm Innovation Center, Inc. All rights reserved. >>> + */ >>> + >>> +#include "pcie-designware.h" >> >> You only need a forward declaration: >> >> struct dw_pcie; >> >>> + >>> +void qcom_pcie_common_set_16gt_eq_settings(struct dw_pcie *pci); >> >> Compile guard still missing. >> >> Johan >