From: Javier Martinez Canillas <javier@osg.samsung.com>
To: Krzysztof Kozlowski <k.kozlowski@samsung.com>,
Sangbeom Kim <sbkim73@samsung.com>,
Liam Girdwood <lgirdwood@gmail.com>,
Mark Brown <broonie@kernel.org>, Lee Jones <lee.jones@linaro.org>,
linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH v2] regulator: s2mps11: Set default ramp delay for S2MPS11 LDOs
Date: Mon, 18 Apr 2016 13:03:22 -0400 [thread overview]
Message-ID: <5715135A.4010402@osg.samsung.com> (raw)
In-Reply-To: <1460986390-9674-1-git-send-email-k.kozlowski@samsung.com>
Hello Krzysztof,
On 04/18/2016 09:33 AM, Krzysztof Kozlowski wrote:
> Driver did not provide default value for ramp delay for LDOs which lead
> to warning in dmesg, e.g. on Odroid XU4:
>
> [ 1.486076] vdd_ldo9: ramp_delay not set
> [ 1.506875] vddq_mmc2: ramp_delay not set
> [ 1.523766] vdd_ldo15: ramp_delay not set
> [ 1.544702] vdd_sd: ramp_delay not set
>
> The datasheet for all the S2MPS1x family is inconsistent here and does
> not specify unambiguously the value of ramp delay for LDO. It mentions
> 30 mV/us in one timing diagram but then omits it completely in LDO
> regulator characteristics table (it is specified for bucks).
>
> However the vendor kernels for Galaxy S5 and Odroid XU3 use values of 12
> mV/us or 24 mV/us.
>
> Without the ramp delay value the consumers do not wait for voltage
> settle after changing it. Although the proper value of ramp delay for
> LDOs is unknown, it seems safer to use at least some value from
> reference kernel than to leave it unset.
>
> Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Best regards,
--
Javier Martinez Canillas
Open Source Group
Samsung Research America
next prev parent reply other threads:[~2016-04-18 17:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-18 13:33 [PATCH v2] regulator: s2mps11: Set default ramp delay for S2MPS11 LDOs Krzysztof Kozlowski
2016-04-18 17:03 ` Javier Martinez Canillas [this message]
2016-04-18 19:04 ` Applied "regulator: s2mps11: Set default ramp delay for S2MPS11 LDOs" to the regulator tree Mark Brown
2016-04-18 19:04 ` Mark Brown
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