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Mon, 24 Feb 2025 07:24:18 -0800 (PST) Received: from [192.168.1.100] ([46.248.82.114]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-abb9f8442c0sm1531734566b.150.2025.02.24.07.24.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 24 Feb 2025 07:24:17 -0800 (PST) Message-ID: Date: Mon, 24 Feb 2025 16:24:14 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.15.1 Subject: Re: [PATCH 03/17] x86: Replace open-coded parity calculation with parity8() To: Kuan-Wei Chiu , tglx@linutronix.de, Ingo Molnar , bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, jk@ozlabs.org, joel@jms.id.au, eajames@linux.ibm.com, andrzej.hajda@intel.com, neil.armstrong@linaro.org, rfoss@kernel.org, maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@gmail.com, simona@ffwll.ch, dmitry.torokhov@gmail.com, mchehab@kernel.org, awalls@md.metrocast.net, hverkuil@xs4all.nl, miquel.raynal@bootlin.com, richard@nod.at, vigneshr@ti.com, louis.peens@corigine.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, parthiban.veerasooran@microchip.com, arend.vanspriel@broadcom.com, johannes@sipsolutions.net, gregkh@linuxfoundation.org, jirislaby@kernel.org, yury.norov@gmail.com, akpm@linux-foundation.org, mingo@kernel.org Cc: hpa@zytor.com, alistair@popple.id.au, linux@rasmusvillemoes.dk, Laurent.pinchart@ideasonboard.com, jonas@kwiboo.se, jernej.skrabec@gmail.com, kuba@kernel.org, linux-kernel@vger.kernel.org, linux-fsi@lists.ozlabs.org, dri-devel@lists.freedesktop.org, linux-input@vger.kernel.org, linux-media@vger.kernel.org, linux-mtd@lists.infradead.org, oss-drivers@corigine.com, netdev@vger.kernel.org, linux-wireless@vger.kernel.org, brcm80211@lists.linux.dev, brcm80211-dev-list.pdl@broadcom.com, linux-serial@vger.kernel.org, bpf@vger.kernel.org, jserv@ccns.ncku.edu.tw, Yu-Chun Lin References: <20250223164217.2139331-1-visitorckw@gmail.com> <20250223164217.2139331-4-visitorckw@gmail.com> Content-Language: en-US From: Uros Bizjak In-Reply-To: <20250223164217.2139331-4-visitorckw@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On 23. 02. 25 17:42, Kuan-Wei Chiu wrote: > Refactor parity calculations to use the standard parity8() helper. This > change eliminates redundant implementations and improves code > efficiency. The patch improves parity assembly code in bootflag.o from: 58: 89 de mov %ebx,%esi 5a: b9 08 00 00 00 mov $0x8,%ecx 5f: 31 d2 xor %edx,%edx 61: 89 f0 mov %esi,%eax 63: 89 d7 mov %edx,%edi 65: 40 d0 ee shr %sil 68: 83 e0 01 and $0x1,%eax 6b: 31 c2 xor %eax,%edx 6d: 83 e9 01 sub $0x1,%ecx 70: 75 ef jne 61 72: 39 c7 cmp %eax,%edi 74: 74 7f je f5 76: to: 54: 89 d8 mov %ebx,%eax 56: ba 96 69 00 00 mov $0x6996,%edx 5b: c0 e8 04 shr $0x4,%al 5e: 31 d8 xor %ebx,%eax 60: 83 e0 0f and $0xf,%eax 63: 0f a3 c2 bt %eax,%edx 66: 73 64 jae cc 68: which is faster and smaller (-10 bytes) code. Reviewed-by: Uros Bizjak Thanks, Uros. > > Co-developed-by: Yu-Chun Lin > Signed-off-by: Yu-Chun Lin > Signed-off-by: Kuan-Wei Chiu > --- > arch/x86/kernel/bootflag.c | 18 +++--------------- > 1 file changed, 3 insertions(+), 15 deletions(-) > > diff --git a/arch/x86/kernel/bootflag.c b/arch/x86/kernel/bootflag.c > index 3fed7ae58b60..314ff0e84900 100644 > --- a/arch/x86/kernel/bootflag.c > +++ b/arch/x86/kernel/bootflag.c > @@ -8,6 +8,7 @@ > #include > #include > #include > +#include > #include > > #include > @@ -20,26 +21,13 @@ > > int sbf_port __initdata = -1; /* set via acpi_boot_init() */ > > -static int __init parity(u8 v) > -{ > - int x = 0; > - int i; > - > - for (i = 0; i < 8; i++) { > - x ^= (v & 1); > - v >>= 1; > - } > - > - return x; > -} > - > static void __init sbf_write(u8 v) > { > unsigned long flags; > > if (sbf_port != -1) { > v &= ~SBF_PARITY; > - if (!parity(v)) > + if (!parity8(v)) > v |= SBF_PARITY; > > printk(KERN_INFO "Simple Boot Flag at 0x%x set to 0x%x\n", > @@ -70,7 +58,7 @@ static int __init sbf_value_valid(u8 v) > { > if (v & SBF_RESERVED) /* Reserved bits */ > return 0; > - if (!parity(v)) > + if (!parity8(v)) > return 0; > > return 1;