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Mon, 23 Dec 2024 16:43:40 +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 4BNGhdNc008284 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 23 Dec 2024 16:43:39 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; Mon, 23 Dec 2024 08:43:33 -0800 Message-ID: <7bc9f3f2-851c-3703-39b4-fea93d10bd7f@quicinc.com> Date: Mon, 23 Dec 2024 22:13:29 +0530 Precedence: bulk X-Mailing-List: linux-kernel@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 , Konrad Dybcio CC: 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> 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-GUID: tZgvjdUIjB8W1rT4w_Xn6YZPXIQBibYo X-Proofpoint-ORIG-GUID: tZgvjdUIjB8W1rT4w_Xn6YZPXIQBibYo 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 mlxlogscore=999 priorityscore=1501 mlxscore=0 clxscore=1015 lowpriorityscore=0 phishscore=0 malwarescore=0 spamscore=0 bulkscore=0 suspectscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2412230148 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. - Krishna Chaitanya. >>>> +}; >>> >>> Empty lines before and after the struct definition. >>> >> ack. >> >> - Krishna Chaitanya. >>>> #ifdef CONFIG_OF >>>> int of_pci_parse_bus_range(struct device_node *node, struct resource *res); >>>> int of_get_pci_domain_nr(struct device_node *node); >>>> @@ -746,7 +751,9 @@ void pci_set_bus_of_node(struct pci_bus *bus); >>>> void pci_release_bus_of_node(struct pci_bus *bus); >>>> int devm_of_pci_bridge_init(struct device *dev, struct pci_host_bridge *bridge); >>>> - >>>> +int of_pci_get_equalization_presets(struct device *dev, >>>> + struct pci_eq_presets *presets, >>>> + int num_lanes); >>> >>> Keep the empty line. >>> >>>> #else >>>> static inline int >>>> of_pci_parse_bus_range(struct device_node *node, struct resource *res) >>>> @@ -793,6 +800,12 @@ static inline int devm_of_pci_bridge_init(struct device *dev, struct pci_host_br >>>> return 0; >>>> } >>>> +static inline int of_pci_get_equalization_presets(struct device *dev, >>>> + struct pci_eq_presets *presets, >>>> + int num_lanes) >>>> +{ >>>> + return 0; >>>> +} >>>> #endif /* CONFIG_OF */ >>>> struct of_changeset; >>>> >>>> -- >>>> 2.34.1 >>>> >>> >