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Tue, 24 Dec 2024 09:17:10 +0000 (GMT) Received: from nalasex01a.na.qualcomm.com (nalasex01a.na.qualcomm.com [10.47.209.196]) by NALASPPMTA03.qualcomm.com (8.18.1.2/8.18.1.2) with ESMTPS id 4BO9H9OP014280 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 24 Dec 2024 09:17:09 GMT Received: from [10.216.2.152] (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Tue, 24 Dec 2024 01:17:03 -0800 Message-ID: <49ccd5f2-8524-eba4-25ef-4cdc39edc93b@quicinc.com> Date: Tue, 24 Dec 2024 14:47:00 +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/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH v3 2/4] PCI: of: Add API to retrieve equalization presets from device tree Content-Language: en-US To: Dmitry Baryshkov CC: Konrad Dybcio , Krishna Chaitanya Chundru , Rob Herring , "Krzysztof Kozlowski" , Conor Dooley , "Bjorn Helgaas" , Jingoo Han , "Manivannan Sadhasivam" , Lorenzo Pieralisi , =?UTF-8?Q?Krzysztof_Wilczy=c5=84ski?= , , , , , , , , Bjorn Andersson References: <20241223-preset_v2-v3-0-a339f475caf5@oss.qualcomm.com> <20241223-preset_v2-v3-2-a339f475caf5@oss.qualcomm.com> <7bc9f3f2-851c-3703-39b4-fea93d10bd7f@quicinc.com> From: Krishna Chaitanya Chundru In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Proofpoint-ORIG-GUID: DAHgdLhOTEMqnrg8ac9W1yw7AexkoagL X-Proofpoint-GUID: DAHgdLhOTEMqnrg8ac9W1yw7AexkoagL 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=2024-09-06_09,2024-09-06_01,2024-09-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 adultscore=0 malwarescore=0 lowpriorityscore=0 bulkscore=0 phishscore=0 mlxscore=0 suspectscore=0 priorityscore=1501 impostorscore=0 mlxlogscore=999 clxscore=1015 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2412240078 On 12/24/2024 12:00 AM, Dmitry Baryshkov wrote: > On Mon, Dec 23, 2024 at 10:13:29PM +0530, Krishna Chaitanya Chundru wrote: >> >> >> On 12/23/2024 8:56 PM, Dmitry Baryshkov wrote: >>> On Mon, Dec 23, 2024 at 08:02:23PM +0530, Krishna Chaitanya Chundru wrote: >>>> >>>> >>>> On 12/23/2024 5:17 PM, Dmitry Baryshkov wrote: >>>>> On Mon, Dec 23, 2024 at 12:21:15PM +0530, Krishna Chaitanya Chundru wrote: >>>>>> PCIe equalization presets are predefined settings used to optimize >>>>>> signal integrity by compensating for signal loss and distortion in >>>>>> high-speed data transmission. >>>>>> >>>>>> As per PCIe spec 6.0.1 revision section 8.3.3.3 & 4.2.4 for data rates >>>>>> of 8.0 GT/s, 16.0 GT/s, 32.0 GT/s, and 64.0 GT/s, there is a way to >>>>>> configure lane equalization presets for each lane to enhance the PCIe >>>>>> link reliability. Each preset value represents a different combination >>>>>> of pre-shoot and de-emphasis values. For each data rate, different >>>>>> registers are defined: for 8.0 GT/s, registers are defined in section >>>>>> 7.7.3.4; for 16.0 GT/s, in section 7.7.5.9, etc. The 8.0 GT/s rate has >>>>>> an extra receiver preset hint, requiring 16 bits per lane, while the >>>>>> remaining data rates use 8 bits per lane. >>>>>> >>>>>> Based on the number of lanes and the supported data rate, this function >>>>>> reads the device tree property and stores in the presets structure. >>>>>> >>>>>> Signed-off-by: Krishna Chaitanya Chundru >>>>>> --- >>>>>> drivers/pci/of.c | 45 +++++++++++++++++++++++++++++++++++++++++++++ >>>>>> drivers/pci/pci.h | 17 +++++++++++++++-- >>>>>> 2 files changed, 60 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/drivers/pci/of.c b/drivers/pci/of.c >>>>>> index dacea3fc5128..99e0e7ae12e9 100644 >>>>>> --- a/drivers/pci/of.c >>>>>> +++ b/drivers/pci/of.c >>>>>> @@ -826,3 +826,48 @@ u32 of_pci_get_slot_power_limit(struct device_node *node, >>>>>> return slot_power_limit_mw; >>>>>> } >>>>>> EXPORT_SYMBOL_GPL(of_pci_get_slot_power_limit); >>>>>> + >>>>> >>>>> kerneldoc? Define who should free the memory and how. >>>>> >>>> I will update this in next series. >>>> as we are allocating using devm_kzalloc it should be freed on driver >>>> detach, as no special freeing is required. >>>>>> +int of_pci_get_equalization_presets(struct device *dev, >>>>>> + struct pci_eq_presets *presets, >>>>>> + int num_lanes) >>>>>> +{ >>>>>> + char name[20]; >>>>>> + void **preset; >>>>>> + void *temp; >>>>>> + int ret; >>>>>> + >>>>>> + if (of_property_present(dev->of_node, "eq-presets-8gts")) { >>>>>> + presets->eq_presets_8gts = devm_kzalloc(dev, sizeof(u16) * num_lanes, GFP_KERNEL); >>>>>> + if (!presets->eq_presets_8gts) >>>>>> + return -ENOMEM; >>>>>> + >>>>>> + ret = of_property_read_u16_array(dev->of_node, "eq-presets-8gts", >>>>>> + presets->eq_presets_8gts, num_lanes); >>>>>> + if (ret) { >>>>>> + dev_err(dev, "Error reading eq-presets-8gts %d\n", ret); >>>>>> + return ret; >>>>>> + } >>>>>> + } >>>>>> + >>>>>> + for (int i = 1; i < sizeof(struct pci_eq_presets) / sizeof(void *); i++) { >>>>>> + snprintf(name, sizeof(name), "eq-presets-%dgts", 8 << i); >>>>>> + if (of_property_present(dev->of_node, name)) { >>>>>> + temp = devm_kzalloc(dev, sizeof(u8) * num_lanes, GFP_KERNEL); >>>>>> + if (!temp) >>>>>> + return -ENOMEM; >>>>>> + >>>>>> + ret = of_property_read_u8_array(dev->of_node, name, >>>>>> + temp, num_lanes); >>>>>> + if (ret) { >>>>>> + dev_err(dev, "Error %s %d\n", name, ret); >>>>>> + return ret; >>>>>> + } >>>>>> + >>>>>> + preset = (void **)((u8 *)presets + i * sizeof(void *)); >>>>> >>>>> Ugh. >>>>> >>>> I was trying iterate over each element on the structure as presets holds the >>>> starting address of the structure and to that we are adding size of the void >>>> * point to go to each element. I did this way to reduce the >>>> redundant code to read all the gts which has same way of storing the data >>>> from the device tree. I will add comments here in the next series. >>> >>> Please rewrite this in a cleaner way. The code shouldn't raise >>> questions. >>> >>>>>> + *preset = temp; >>>>>> + } >>>>>> + } >>>>>> + >>>>>> + return 0; >>>>>> +} >>>>>> +EXPORT_SYMBOL_GPL(of_pci_get_equalization_presets); >>>>>> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h >>>>>> index 14d00ce45bfa..82362d58bedc 100644 >>>>>> --- a/drivers/pci/pci.h >>>>>> +++ b/drivers/pci/pci.h >>>>>> @@ -731,7 +731,12 @@ static inline u64 pci_rebar_size_to_bytes(int size) >>>>>> } >>>>>> struct device_node; >>>>>> - >>>>>> +struct pci_eq_presets { >>>>>> + void *eq_presets_8gts; >>>>>> + void *eq_presets_16gts; >>>>>> + void *eq_presets_32gts; >>>>>> + void *eq_presets_64gts; >>>>> >>>>> Why are all of those void*? 8gts is u16*, all other are u8*. >>>>> >>>> To have common parsing logic I moved them to void*, as these are pointers >>>> actual memory is allocated by of_pci_get_equalization_presets() >>>> based upon the gts these should not give any issues. >>> >>> Please, don't. They have types. void pointers are for the opaque data. >>> >> ok. >> >> I think then better to use v1 patch >> https://lore.kernel.org/all/20241116-presets-v1-2-878a837a4fee@quicinc.com/ >> >> konrad, any objection on using v1 as that will be cleaner way even if we >> have some repetitive code. > > Konrad had a nice suggestion about using the array of values. Please use > such an array for 16gts and above. This removes most of repetitive code. > I don't feel having array in the preset structure looks good, I have come up with this logic if you feel it is not so good I will go to the suggested way by having array for 16gts and above. if (of_property_present(dev->of_node, "eq-presets-8gts")) { presets->eq_presets_8gts = devm_kzalloc(dev, sizeof(u16) * num_lanes, GFP_KERNEL); if (!presets->eq_presets_8gts) return -ENOMEM; ret = of_property_read_u16_array(dev->of_node, "eq-presets-8gts", presets->eq_presets_8gts, num_lanes); if (ret) { dev_err(dev, "Error reading eq-presets-8gts %d\n", ret); return ret; } } for (int i = EQ_PRESET_TYPE_16GTS; i < EQ_PRESET_TYPE_64GTS; i++) { snprintf(name, sizeof(name), "eq-presets-%dgts", 8 << i); if (of_property_present(dev->of_node, name)) { temp = devm_kzalloc(dev, sizeof(u8) * num_lanes, GFP_KERNEL); if (!temp) return -ENOMEM; ret = of_property_read_u8_array(dev->of_node, name, temp, num_lanes); if (ret) { dev_err(dev, "Error %s %d\n", name, ret); return ret; } switch (i) { case EQ_PRESET_TYPE_16GTS: presets->eq_presets_16gts = temp; break; case EQ_PRESET_TYPE_32GTS: presets->eq_presets_32gts = temp; break; case EQ_PRESET_TYPE_64GTS: presets->eq_presets_64gts = temp; break; } } } - Krishna Chaitanya. >