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[149.232.183.2]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-466648c5413sm20505403f8f.11.2026.06.21.13.13.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 21 Jun 2026 13:14:00 -0700 (PDT) Message-ID: <2f37b826-b760-4735-bc33-e1f167729d52@broadcom.com> Date: Sun, 21 Jun 2026 22:13:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] pmdomain: bcm: bcm2835-power: Raise ASB poll timeout to 100us To: =?UTF-8?Q?Ma=C3=ADra_Canal?= , Stefan Wahren , Ulf Hansson , Broadcom internal kernel review list , Ray Jui , Scott Branden Cc: linux-pm@vger.kernel.org, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, kernel-dev@igalia.com References: <20260530204636.1115120-1-mcanal@igalia.com> <4af63689-e08c-406e-9ec3-f56dcbfb6f91@igalia.com> Content-Language: en-US From: Florian Fainelli Autocrypt: addr=florian.fainelli@broadcom.com; keydata= xsBNBFPAG8ABCAC3EO02urEwipgbUNJ1r6oI2Vr/+uE389lSEShN2PmL3MVnzhViSAtrYxeT M0Txqn1tOWoIc4QUl6Ggqf5KP6FoRkCrgMMTnUAINsINYXK+3OLe7HjP10h2jDRX4Ajs4Ghs JrZOBru6rH0YrgAhr6O5gG7NE1jhly+EsOa2MpwOiXO4DE/YKZGuVe6Bh87WqmILs9KvnNrQ PcycQnYKTVpqE95d4M824M5cuRB6D1GrYovCsjA9uxo22kPdOoQRAu5gBBn3AdtALFyQj9DQ KQuc39/i/Kt6XLZ/RsBc6qLs+p+JnEuPJngTSfWvzGjpx0nkwCMi4yBb+xk7Hki4kEslABEB AAHNMEZsb3JpYW4gRmFpbmVsbGkgPGZsb3JpYW4uZmFpbmVsbGlAYnJvYWRjb20uY29tPsLB IQQQAQgAywUCZWl41AUJI+Jo+hcKAAG/SMv+fS3xUQWa0NryPuoRGjsA3SAUAAAAAAAWAAFr ZXktdXNhZ2UtbWFza0BwZ3AuY29tjDAUgAAAAAAgAAdwcmVmZXJyZWQtZW1haWwtZW5jb2Rp bmdAcGdwLmNvbXBncG1pbWUICwkIBwMCAQoFF4AAAAAZGGxkYXA6Ly9rZXlzLmJyb2FkY29t Lm5ldAUbAwAAAAMWAgEFHgEAAAAEFQgJChYhBNXZKpfnkVze1+R8aIExtcQpvGagAAoJEIEx tcQpvGagWPEH/2l0DNr9QkTwJUxOoP9wgHfmVhqc0ZlDsBFv91I3BbhGKI5UATbipKNqG13Z TsBrJHcrnCqnTRS+8n9/myOF0ng2A4YT0EJnayzHugXm+hrkO5O9UEPJ8a+0553VqyoFhHqA zjxj8fUu1px5cbb4R9G4UAySqyeLLeqnYLCKb4+GklGSBGsLMYvLmIDNYlkhMdnnzsSUAS61 WJYW6jjnzMwuKJ0ZHv7xZvSHyhIsFRiYiEs44kiYjbUUMcXor/uLEuTIazGrE3MahuGdjpT2 IOjoMiTsbMc0yfhHp6G/2E769oDXMVxCCbMVpA+LUtVIQEA+8Zr6mX0Yk4nDS7OiBlvOwE0E U8AbwQEIAKxr71oqe+0+MYCc7WafWEcpQHFUwvYLcdBoOnmJPxDwDRpvU5LhqSPvk/yJdh9k 4xUDQu3rm1qIW2I9Puk5n/Jz/lZsqGw8T13DKyu8eMcvaA/irm9lX9El27DPHy/0qsxmxVmU pu9y9S+BmaMb2CM9IuyxMWEl9ruWFS2jAWh/R8CrdnL6+zLk60R7XGzmSJqF09vYNlJ6Bdbs MWDXkYWWP5Ub1ZJGNJQ4qT7g8IN0qXxzLQsmz6tbgLMEHYBGx80bBF8AkdThd6SLhreCN7Uh IR/5NXGqotAZao2xlDpJLuOMQtoH9WVNuuxQQZHVd8if+yp6yRJ5DAmIUt5CCPcAEQEAAcLB gQQYAQIBKwUCU8AbwgUbDAAAAMBdIAQZAQgABgUCU8AbwQAKCRCTYAaomC8PVQ0VCACWk3n+ obFABEp5Rg6Qvspi9kWXcwCcfZV41OIYWhXMoc57ssjCand5noZi8bKg0bxw4qsg+9cNgZ3P N/DFWcNKcAT3Z2/4fTnJqdJS//YcEhlr8uGs+ZWFcqAPbteFCM4dGDRruo69IrHfyyQGx16s CcFlrN8vD066RKevFepb/ml7eYEdN5SRALyEdQMKeCSf3mectdoECEqdF/MWpfWIYQ1hEfdm C2Kztm+h3Nkt9ZQLqc3wsPJZmbD9T0c9Rphfypgw/SfTf2/CHoYVkKqwUIzI59itl5Lze+R5 wDByhWHx2Ud2R7SudmT9XK1e0x7W7a5z11Q6vrzuED5nQvkhAAoJEIExtcQpvGagugcIAJd5 EYe6KM6Y6RvI6TvHp+QgbU5dxvjqSiSvam0Ms3QrLidCtantcGT2Wz/2PlbZqkoJxMQc40rb fXa4xQSvJYj0GWpadrDJUvUu3LEsunDCxdWrmbmwGRKqZraV2oG7YEddmDqOe0Xm/NxeSobc MIlnaE6V0U8f5zNHB7Y46yJjjYT/Ds1TJo3pvwevDWPvv6rdBeV07D9s43frUS6xYd1uFxHC 7dZYWJjZmyUf5evr1W1gCgwLXG0PEi9n3qmz1lelQ8lSocmvxBKtMbX/OKhAfuP/iIwnTsww 95A2SaPiQZA51NywV8OFgsN0ITl2PlZ4Tp9hHERDe6nQCsNI/Us= In-Reply-To: <4af63689-e08c-406e-9ec3-f56dcbfb6f91@igalia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-DetectorID-Processed: b00c1d49-9d2e-4205-b15f-d015386d3d5e X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260621_131405_202916_5D6FD1B7 X-CRM114-Status: GOOD ( 18.93 ) X-BeenThere: linux-arm-kernel@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-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 6/19/2026 2:57 PM, Maíra Canal wrote: > Hi, > > On 31/05/26 09:18, Maíra Canal wrote: >> Hi Stefan, >> >> On 31/05/26 07:41, Stefan Wahren wrote: >>> Hi Maíra, >>> >>> Am 30.05.26 um 22:46 schrieb Maíra Canal: >>>> Commit 18605b1b936b ("pmdomain: bcm: bcm2835-power: Increase ASB >>>> control >>>> timeout") raised the ASB handshake polling budget from 1us to 5us. >>>> Surveying the pmdomain subsystem, 5us is still one of the smallest >>>> polling >>>> budgets by a wide margin. Comparable handshakes in other drivers use: >>>> >>>>    - 100us : starfive jh71xx-pmu, apple pmgr-pwrstate >>>>    - 1ms   : renesas rcar-sysc, rmobile-sysc (power-on) >>>>    - 10ms  : renesas rcar-gen4-sysc, sunxi sun55i-pck600 >>>>    - 1s    : mediatek mtk-pm-domains, mtk-scpsys >>>> >>>> Raise the BCM2835 timeout to 100us, matching analogous drivers. >>>> 100us is >>>> still negligible relative to a power-domain transition and gives the >>>> V3D >>>> master ASB substantially more headroom to drain under heavy workloads, >>>> assuring us that the timeout is enough for any scenario. >>> tbh I'm not convinced by this explanation. Starting with a timeout >>> comparison across different pmdomain driver looks strange to me. >>> >>> My expectation that the reason for such a patch is that there is some >>> kind of scenario to trigger unexpected timeouts. >>> If this is the case, please provide more information about the >>> scenario (specific platform, scenario, link to the bug report). >> >> The context: I was debugging this issue [1] and initially I had the >> intuition that it could be related to a timeout in the ASB polling loop. >> As I don't have access to the BCM2835 SoC datasheet (the public one >> doesn't have PM information), I started to check other driver's >> handshake timeout to see if ours was comparable to similar drivers. As >> you can see, our timeout is much smaller. >> >> In the end, issue [1] wasn't related to the pmdomain driver, so I don't >> have a specific scenario to trigger this issue. Even though, I sent this >> patch considering the comparison to other drivers with the goal to be >> conservative and use a larger timeout that could accommodate an extreme >> scenario. However, if you believe it's unreasonable, I'm okay dropping >> this patch. >> >> Ideally, it would be great to have information from Broadcom on what's >> the largest possible time required to perform a power transition. Maybe >> Florian could help us with that? >> > > Gentle ping, any ideas about this? I think it's reasonable in the sense that if there is a lot of traffic posted on the AXI asynchronous bridge it will take longer for the acknowledgement to come, I asked the designers whether 100us is reasonable or not and will get back to you as soon as I get an answer. -- Florian