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b=EqoY+K4yCtaCeH/Hkx0Cxm77pepPRptfPJPL5pRuSZlaEAYgezTYCHH8cJ7Ko9VzBY1oy1DOafKxZT6CCqq3s8RKkB0WNE9beA1Yygr4im3bKQzMH7bRua9oH/vzusRCHzgQ+ydE5Ofs19wGORrWhWbqLaxKJytAFsAaH78vKhQ= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from CH3PR12MB7523.namprd12.prod.outlook.com (2603:10b6:610:148::13) by BN5PR12MB9461.namprd12.prod.outlook.com (2603:10b6:408:2a8::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9031.15; Fri, 15 Aug 2025 09:38:26 +0000 Received: from CH3PR12MB7523.namprd12.prod.outlook.com ([fe80::f722:9f71:3c1a:f216]) by CH3PR12MB7523.namprd12.prod.outlook.com ([fe80::f722:9f71:3c1a:f216%6]) with mapi id 15.20.9031.014; Fri, 15 Aug 2025 09:38:26 +0000 Message-ID: <595d754a-c8c2-4ef0-bdbd-3ff25330224a@amd.com> Date: Fri, 15 Aug 2025 15:08:20 +0530 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 net-next] amd-xgbe: Configure and retrieve 'tx-usecs' for Tx coalescing To: Jakub Kicinski Cc: Shyam-sundar.S-k@amd.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <20250812045035.3376179-1-Vishal.Badole@amd.com> <20250813170012.7436b6e6@kernel.org> Content-Language: en-US From: "Badole, Vishal" In-Reply-To: <20250813170012.7436b6e6@kernel.org> Content-Type: text/plain; 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My intent was to highlight that while ethtool has gained more advanced and configurable options over time, the driver in its current form does not have support for tx-usecs configuration using Ethool. I’ll reword the sentence to make this clearer in next patch version.> >> + /* Check if both tx_usecs and tx_frames are set to 0 simultaneously */ >> + if (!tx_usecs && !tx_frames) { >> + NL_SET_ERR_MSG_FMT_MOD(extack, >> + "tx_usecs and tx_frames must not be 0 together"); >> + return -EINVAL; >> + } >> + >> /* Check the bounds of values for Tx */ >> + if (tx_usecs > XGMAC_MAX_COAL_TX_TICK) { >> + NL_SET_ERR_MSG_FMT_MOD(extack, "tx-usecs is limited to %d usec", >> + XGMAC_MAX_COAL_TX_TICK); >> + return -EINVAL; >> + } > > Normal configuration granularity for this parameter is in 10s of usecs. > You seem to be using a timer, so I think you should either round the > value up / down to what the jiffy resolution will give you or > reject configuration that's not expressible in jiffies (not a multiple > of jiffies_to_usecs(1)). Otherwise users may waste time turning this > knob by 100usec which will have zero effect. Good point — the hardware uses a timer, so sub-jiffy resolution won’t have any real effect. I’ll update the code in next patch version to round the tx-usecs value to the nearest multiple.