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Wed, 02 Oct 2024 05:41:24 -0700 (PDT) Received: from [192.168.2.177] ([207.188.162.240]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a93c27c7237sm858830866b.81.2024.10.02.05.41.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Oct 2024 05:41:23 -0700 (PDT) Message-ID: <7d577541-cada-4f6f-8e83-c420dd0e9382@gmail.com> Date: Wed, 2 Oct 2024 14:41:22 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 2/3] soc: mediatek: mtk-cmdq: Mark very unlikely branches as such To: AngeloGioacchino Del Regno , linux-mediatek@lists.infradead.org Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kernel@collabora.com References: <20240918100620.103536-1-angelogioacchino.delregno@collabora.com> <20240918100620.103536-3-angelogioacchino.delregno@collabora.com> Content-Language: en-US, ca-ES, es-ES From: Matthias Brugger Autocrypt: addr=matthias.bgg@gmail.com; keydata= xsFNBFP1zgUBEAC21D6hk7//0kOmsUrE3eZ55kjc9DmFPKIz6l4NggqwQjBNRHIMh04BbCMY fL3eT7ZsYV5nur7zctmJ+vbszoOASXUpfq8M+S5hU2w7sBaVk5rpH9yW8CUWz2+ZpQXPJcFa OhLZuSKB1F5JcvLbETRjNzNU7B3TdS2+zkgQQdEyt7Ij2HXGLJ2w+yG2GuR9/iyCJRf10Okq gTh//XESJZ8S6KlOWbLXRE+yfkKDXQx2Jr1XuVvM3zPqH5FMg8reRVFsQ+vI0b+OlyekT/Xe 0Hwvqkev95GG6x7yseJwI+2ydDH6M5O7fPKFW5mzAdDE2g/K9B4e2tYK6/rA7Fq4cqiAw1+u EgO44+eFgv082xtBez5WNkGn18vtw0LW3ESmKh19u6kEGoi0WZwslCNaGFrS4M7OH+aOJeqK fx5dIv2CEbxc6xnHY7dwkcHikTA4QdbdFeUSuj4YhIZ+0QlDVtS1QEXyvZbZky7ur9rHkZvP ZqlUsLJ2nOqsmahMTIQ8Mgx9SLEShWqD4kOF4zNfPJsgEMB49KbS2o9jxbGB+JKupjNddfxZ HlH1KF8QwCMZEYaTNogrVazuEJzx6JdRpR3sFda/0x5qjTadwIW6Cl9tkqe2h391dOGX1eOA 1ntn9O/39KqSrWNGvm+1raHK+Ev1yPtn0Wxn+0oy1tl67TxUjQARAQABzSlNYXR0aGlhcyBC cnVnZ2VyIDxtYXR0aGlhcy5iZ2dAZ21haWwuY29tPsLBkgQTAQIAPAIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AWIQTmuZIYwPLDJRwsOhfZFAuyVhMC8QUCWt3scQIZAQAKCRDZFAuy VhMC8WzRD/4onkC+gCxG+dvui5SXCJ7bGLCu0xVtiGC673Kz5Aq3heITsERHBV0BqqctOEBy ZozQQe2Hindu9lasOmwfH8+vfTK+2teCgWesoE3g3XKbrOCB4RSrQmXGC3JYx6rcvMlLV/Ch YMRR3qv04BOchnjkGtvm9aZWH52/6XfChyh7XYndTe5F2bqeTjt+kF/ql+xMc4E6pniqIfkv c0wsH4CkBHqoZl9w5e/b9MspTqsU9NszTEOFhy7p2CYw6JEa/vmzR6YDzGs8AihieIXDOfpT DUr0YUlDrwDSrlm/2MjNIPTmSGHH94ScOqu/XmGW/0q1iar/Yr0leomUOeeEzCqQtunqShtE 4Mn2uEixFL+9jiVtMjujr6mphznwpEqObPCZ3IcWqOFEz77rSL+oqFiEA03A2WBDlMm++Sve 9jpkJBLosJRhAYmQ6ey6MFO6Krylw1LXcq5z1XQQavtFRgZoruHZ3XlhT5wcfLJtAqrtfCe0 aQ0kJW+4zj9/So0uxJDAtGuOpDYnmK26dgFN0tAhVuNInEVhtErtLJHeJzFKJzNyQ4GlCaLw jKcwWcqDJcrx9R7LsCu4l2XpKiyxY6fO4O8DnSleVll9NPfAZFZvf8AIy3EQ8BokUsiuUYHz wUo6pclk55PZRaAsHDX/fNr24uC6Eh5oNQ+v4Pax/gtyyc7BTQRd1TlIARAAm78mTny44Hwd IYNK4ZQH6U5pxcJtU45LLBmSr4DK/7er9chpvJ5pgzCGuI25ceNTEg5FChYcgfNMKqwCAekk V9Iegzi6UK448W1eOp8QeQDS6sHpLSOe8np6/zvmUvhiLokk7tZBhGz+Xs5qQmJPXcag7AMi fuEcf88ZSpChmUB3WflJV2DpxF3sSon5Ew2i53umXLqdRIJEw1Zs2puDJaMqwP3wIyMdrfdI H1ZBBJDIWV/53P52mKtYQ0Khje+/AolpKl96opi6o9VLGeqkpeqrKM2cb1bjo5Zmn4lXl6Nv JRH/ZT68zBtOKUtwhSlOB2bE8IDonQZCOYo2w0opiAgyfpbij8uiI7siBE6bWx2fQpsmi4Jr ZBmhDT6n/uYleGW0DRcZmE2UjeekPWUumN13jaVZuhThV65SnhU05chZT8vU1nATAwirMVeX geZGLwxhscduk3nNb5VSsV95EM/KOtilrH69ZL6Xrnw88f6xaaGPdVyUigBTWc/fcWuw1+nk GJDNqjfSvB7ie114R08Q28aYt8LCJRXYM1WuYloTcIhRSXUohGgHmh7usl469/Ra5CFaMhT3 yCVciuHdZh3u+x+O1sRcOhaFW3BkxKEy+ntxw8J7ZzhgFOgi2HGkOGgM9R03A6ywc0sPwbgk gF7HCLirshP2U/qxWy3C8DkAEQEAAcLBdgQYAQgAIBYhBOa5khjA8sMlHCw6F9kUC7JWEwLx BQJd1TlIAhsMAAoJENkUC7JWEwLxtdcP/jHJ9vI8adFi1HQoWUKCQbZdZ5ZJHayFKIzU9kZE /FHzzzMDZYFgcCTs2kmUVyGloStXpZ0WtdCMMB31jBoQe5x9LtICHEip0irNXm80WsyPCEHU 3wx91QkOmDJftm6T8+F3lqhlc3CwJGpoPY7AVlevzXNJfATZR0+Yh9NhON5Ww4AjsZntqQKx E8rrieLRd+he57ZdRKtRRNGKZOS4wetNhodjfnjhr4Z25BAssD5q+x4uaO8ofGxTjOdrSnRh vhzPCgmP7BKRUZA0wNvFxjboIw8rbTiOFGb1Ebrzuqrrr3WFuK4C1YAF4CyXUBL6Z1Lto//i 44ziQUK9diAgfE/8GhXP0JlMwRUBlXNtErJgItR/XAuFwfO6BOI43P19YwEsuyQq+rubW2Wv rWY2Bj2dXDAKUxS4TuLUf2v/b9Rct36ljzbNxeEWt+Yq4IOY6QHnE+w4xVAkfwjT+Vup8sCp +zFJv9fVUpo/bjePOL4PMP1y+PYrp4PmPmRwoklBpy1ep8m8XURv46fGUHUEIsTwPWs2Q87k 7vjYyrcyAOarX2X5pvMQvpAMADGf2Z3wrCsDdG25w2HztweUNd9QEprtJG8GNNzMOD4cQ82T a7eGvPWPeXauWJDLVR9jHtWT9Ot3BQgmApLxACvwvD1a69jaFKov28SPHxUCQ9Y1Y/Ct In-Reply-To: <20240918100620.103536-3-angelogioacchino.delregno@collabora.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241002_054126_935594_8EFBC371 X-CRM114-Status: GOOD ( 19.61 ) X-BeenThere: linux-mediatek@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-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org On 18/09/2024 12:06, AngeloGioacchino Del Regno wrote: > Calling cmdq packet builders with an unsupported event number, > or without left/right operands (in the case of logic commands) > means that the caller (another driver) wants to perform an > unsupported operation, so this means that the caller must be > fixed instead. > > Anyway, such checks are here for safety and, unless any driver > bug or any kind of misconfiguration is present, will always be > false so add a very unlikely hint for those. > > Knowing that CPUs' branch predictors (and compilers, anyway) are > indeed smart about these cases, this is done mainly for human > readability purposes. > Are you really sure we need that? As you mentioned the unlikely() is probably useless as compiler and branch predictions will do the job. I don't see the complexity in the code to have this annotations for human readability. I would argue against using unlikely() here as, in general, it is discouraged to use it. We will just create a data point of doing things that should only be done with very good reason. I don't see the reason here, it will only confuse other developers about the use of likely() and unlikely(). Regards, Matthias > Signed-off-by: AngeloGioacchino Del Regno > --- > drivers/soc/mediatek/mtk-cmdq-helper.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/soc/mediatek/mtk-cmdq-helper.c b/drivers/soc/mediatek/mtk-cmdq-helper.c > index 620c371fd1fc..4ffd1a35df87 100644 > --- a/drivers/soc/mediatek/mtk-cmdq-helper.c > +++ b/drivers/soc/mediatek/mtk-cmdq-helper.c > @@ -336,7 +336,7 @@ int cmdq_pkt_wfe(struct cmdq_pkt *pkt, u16 event, bool clear) > struct cmdq_instruction inst = { {0} }; > u32 clear_option = clear ? CMDQ_WFE_UPDATE : 0; > > - if (event >= CMDQ_MAX_EVENT) > + if (unlikely(event >= CMDQ_MAX_EVENT)) > return -EINVAL; > > inst.op = CMDQ_CODE_WFE; > @@ -351,7 +351,7 @@ int cmdq_pkt_acquire_event(struct cmdq_pkt *pkt, u16 event) > { > struct cmdq_instruction inst = {}; > > - if (event >= CMDQ_MAX_EVENT) > + if (unlikely(event >= CMDQ_MAX_EVENT)) > return -EINVAL; > > inst.op = CMDQ_CODE_WFE; > @@ -366,7 +366,7 @@ int cmdq_pkt_clear_event(struct cmdq_pkt *pkt, u16 event) > { > struct cmdq_instruction inst = { {0} }; > > - if (event >= CMDQ_MAX_EVENT) > + if (unlikely(event >= CMDQ_MAX_EVENT)) > return -EINVAL; > > inst.op = CMDQ_CODE_WFE; > @@ -381,7 +381,7 @@ int cmdq_pkt_set_event(struct cmdq_pkt *pkt, u16 event) > { > struct cmdq_instruction inst = {}; > > - if (event >= CMDQ_MAX_EVENT) > + if (unlikely(event >= CMDQ_MAX_EVENT)) > return -EINVAL; > > inst.op = CMDQ_CODE_WFE; > @@ -476,7 +476,7 @@ int cmdq_pkt_logic_command(struct cmdq_pkt *pkt, u16 result_reg_idx, > { > struct cmdq_instruction inst = { {0} }; > > - if (!left_operand || !right_operand || s_op >= CMDQ_LOGIC_MAX) > + if (unlikely(!left_operand || !right_operand || s_op >= CMDQ_LOGIC_MAX)) > return -EINVAL; > > inst.op = CMDQ_CODE_LOGIC;