From: Shawn Guo <shawnguo@kernel.org>
To: Lucas Stach <l.stach@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>,
Fabio Estevam <festevam@gmail.com>,
NXP Linux Team <linux-imx@nxp.com>,
linux-arm-kernel@lists.infradead.org,
patchwork-lst@pengutronix.de
Subject: Re: [PATCH] ARM: dts: imx6qdl: correct PU regulator ramp delay
Date: Sat, 11 Jun 2022 16:47:46 +0800 [thread overview]
Message-ID: <20220611084746.GE254723@dragon> (raw)
In-Reply-To: <20220511160823.1436562-1-l.stach@pengutronix.de>
On Wed, May 11, 2022 at 06:08:23PM +0200, Lucas Stach wrote:
> Contrary to what was believed at the time, the ramp delay of 150us is not
> plenty for the PU LDO with the default step time of 512 pulses of the 24MHz
> clock. Measurements have shown that after enabling the LDO the voltage on
> VDDPU_CAP jumps to ~750mV in the first step and after that the regulator
> executes the normal ramp up as defined by the step size control.
>
> This means it takes the regulator between 360us and 370us to ramp up to
> the nominal 1.15V voltage for this power domain. With the old setting of
> the ramp delay the power up of the PU GPC domain would happen in the middle
> of the regulator ramp with the voltage being at around 900mV. Apparently
> this was enough for most units to properly power up the peripherals in the
> domain and execute the reset. Some units however, fail to power up properly,
> especially when the chip is at a low temperature. In that case any access
> to the GPU registers would yield an incorrect result with no way to recover
> from this situation.
>
> Change the ramp delay to 380us to cover the measured ramp up time with a
> bit of additional slack.
>
> Fixes: 40130d327f72 ("ARM: dts: imx6qdl: Allow disabling the PU regulator,
> add a enable ramp delay")
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Applied, thanks!
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prev parent reply other threads:[~2022-06-11 8:49 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-11 16:08 [PATCH] ARM: dts: imx6qdl: correct PU regulator ramp delay Lucas Stach
2022-05-11 18:38 ` Francesco Dolcini
2022-06-11 8:47 ` Shawn Guo [this message]
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