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Tue, 30 Dec 2025 14:12:33 -0600 Received: from localhost (uda0133052.dhcp.ti.com [128.247.81.232]) by lelvem-mr06.itg.ti.com (8.18.1/8.18.1) with ESMTP id 5BUKCXQr1206900; Tue, 30 Dec 2025 14:12:33 -0600 Date: Tue, 30 Dec 2025 14:12:33 -0600 From: Nishanth Menon To: Michael Walle CC: Frank Binns , Matt Coster , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Rob Herring , "Krzysztof Kozlowski" , Conor Dooley , "Vignesh Raghavendra" , Tero Kristo , Andrew Davis , Santosh Shilimkar , Michael Turquette , Stephen Boyd , Kevin Hilman , Randolph Sapp , , , , , Subject: Re: [PATCH v2 2/4] clk: keystone: don't cache clock rate Message-ID: <20251230201233.n36d5fiensqyb6fc@splice> References: <20251223124729.2482877-1-mwalle@kernel.org> <20251223124729.2482877-3-mwalle@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20251223124729.2482877-3-mwalle@kernel.org> X-C2ProcessedOrg: 333ef613-75bf-4e12-a4b1-8e3623f5dcea X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: BN2PEPF000044A8:EE_|IA1PR10MB7285:EE_ X-MS-Office365-Filtering-Correlation-Id: d20f1127-0f02-41bf-76bd-08de47dfc9ef X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|82310400026|36860700013|7416014|376014; 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X-OriginatorOrg: ti.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 30 Dec 2025 20:12:42.3304 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: d20f1127-0f02-41bf-76bd-08de47dfc9ef X-MS-Exchange-CrossTenant-Id: e5b49634-450b-4709-8abb-1e2b19b982b7 X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=e5b49634-450b-4709-8abb-1e2b19b982b7;Ip=[198.47.21.194];Helo=[flwvzet200.ext.ti.com] X-MS-Exchange-CrossTenant-AuthSource: BN2PEPF000044A8.namprd04.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA1PR10MB7285 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251230_121251_569436_729D3932 X-CRM114-Status: GOOD ( 22.49 ) 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 13:47-20251223, Michael Walle wrote: > The TISCI firmware will return 0 if the clock or consumer is not > enabled although there is a stored value in the firmware. IOW a call to > set rate will work but at get rate will always return 0 if the clock is > disabled. > The clk framework will try to cache the clock rate when it's requested > by a consumer. If the clock or consumer is not enabled at that point, > the cached value is 0, which is wrong. Thus, disable the cache > altogether. > > Signed-off-by: Michael Walle > Reviewed-by: Kevin Hilman > Reviewed-by: Randolph Sapp > --- > drivers/clk/keystone/sci-clk.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/clk/keystone/sci-clk.c b/drivers/clk/keystone/sci-clk.c > index 9d5071223f4c..0a1565fdbb3b 100644 > --- a/drivers/clk/keystone/sci-clk.c > +++ b/drivers/clk/keystone/sci-clk.c > @@ -333,6 +333,14 @@ static int _sci_clk_build(struct sci_clk_provider *provider, > > init.ops = &sci_clk_ops; > init.num_parents = sci_clk->num_parents; > + > + /* > + * A clock rate query to the SCI firmware will return 0 if either the > + * clock itself is disabled or the attached device/consumer is disabled. > + * This makes it inherently unsuitable for the caching of the clk > + * framework. > + */ > + init.flags = CLK_GET_RATE_NOCACHE; > sci_clk->hw.init = &init; > > ret = devm_clk_hw_register(provider->dev, &sci_clk->hw); > -- > 2.47.3 > Reviewed-by: Nishanth Menon I wish there was a better scheme, but inherently, just like SCMI and other systems where power management co-processor controls clocks, there is no real feasible caching scheme I can think of. I wonder if Stephen or others have a thought on this? That said, I wonder if we need fixes tag to this? I am sure there are other clocks susceptible to this as well. I wonder if commit 3c13933c6033 ("clk: keystone: sci-clk: add support for dynamically probing clocks") is the appropriate tag? -- Regards, Nishanth Menon Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3 1A34 DDB5 849D 1736 249D https://ti.com/opensource