linux-kernel - Re: [PATCH v2] spi: cadence-quadspi: Parse DT for flashes with the rest of the DT parsing

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Message-ID: <20251204200027.p4osjcj67bcmsvck@skipper>
Date: Thu, 4 Dec 2025 14:00:27 -0600
From: Nishanth Menon <nm@...com>
To: Mark Brown <broonie@...nel.org>
CC: Francesco Dolcini <francesco@...cini.it>, Siddharth Vadapalli
	<s-vadapalli@...com>, Anurag Dutta <a-dutta@...com>,
	<linux-spi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<stable@...r.kernel.org>
Subject: Re: [PATCH v2] spi: cadence-quadspi: Parse DT for flashes with the
 rest of the DT parsing

On 19:13-20251204, Mark Brown wrote:
> The recent refactoring of where runtime PM is enabled done in commit
> f1eb4e792bb1 ("spi: spi-cadence-quadspi: Enable pm runtime earlier to
> avoid imbalance") made the fact that when we do a pm_runtime_disable()
> in the error paths of probe() we can trigger a runtime disable which in
> turn results in duplicate clock disables.  This is particularly likely
> to happen when there is missing or broken DT description for the flashes
> attached to the controller.
> 
> Early on in the probe function we do a pm_runtime_get_noresume() since
> the probe function leaves the device in a powered up state but in the
> error path we can't assume that PM is enabled so we also manually
> disable everything, including clocks. This means that when runtime PM is
> active both it and the probe function release the same reference to the
> main clock for the IP, triggering warnings from the clock subsystem:
> 
> [    8.693719] clk:75:7 already disabled
> [    8.693791] WARNING: CPU: 1 PID: 185 at /usr/src/kernel/drivers/clk/clk.c:1188 clk_core_disable+0xa0/0xb
> ...
> [    8.694261]  clk_core_disable+0xa0/0xb4 (P)
> [    8.694272]  clk_disable+0x38/0x60
> [    8.694283]  cqspi_probe+0x7c8/0xc5c [spi_cadence_quadspi]
> [    8.694309]  platform_probe+0x5c/0xa4
> 
> Dealing with this issue properly is complicated by the fact that we
> don't know if runtime PM is active so can't tell if it will disable the
> clocks or not.  We can, however, sidestep the issue for the flash
> descriptions by moving their parsing to when we parse the controller
> properties which also save us doing a bunch of setup which can never be
> used so let's do that.
> 
> Reported-by: Francesco Dolcini <francesco@...cini.it>
> Closes: https://lore.kernel.org/r/20251201072844.GA6785@francesco-nb
> Signed-off-by: Mark Brown <broonie@...nel.org>
> Cc: stable@...r.kernel.org

https://gist.github.com/nmenon/5ca89b617113e9dbb31d4630586af945#file-gistfile1-txt-L1004
next-20251204 + this patch -> The issue still exists at least on my
platform.

-- 
Regards,
Nishanth Menon
Key (0xDDB5849D1736249D) / Fingerprint: F8A2 8693 54EB 8232 17A3  1A34 DDB5 849D 1736 249D
https://ti.com/opensource