linux-kernel - Re: [PATCH v2 17/22] rtc: pm8xxx: add support for nvmem offset

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Date:   Mon, 6 Feb 2023 19:16:54 -0800
From:   David Collins <quic_collinsd@...cinc.com>
To:     Johan Hovold <johan+linaro@...nel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Bjorn Andersson <andersson@...nel.org>
CC:     Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Maximilian Luz <luzmaximilian@...il.com>,
        <linux-arm-msm@...r.kernel.org>, <linux-rtc@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 17/22] rtc: pm8xxx: add support for nvmem offset

On 2/2/23 07:54, Johan Hovold wrote:
> On many Qualcomm platforms the PMIC RTC control and time registers are
> read-only so that the RTC time can not be updated. Instead an offset

s/can not/cannot/

> needs be stored in some machine-specific non-volatile memory, which the
> driver can take into account.
> 
> Add support for storing a 32-bit offset from the Epoch in an nvmem cell
> so that the RTC time can be set on such platforms.
> 
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  drivers/rtc/rtc-pm8xxx.c | 141 +++++++++++++++++++++++++++++++++++----
>  1 file changed, 129 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-pm8xxx.c b/drivers/rtc/rtc-pm8xxx.c
> index eff2782beeed..372494e82f40 100644
> --- a/drivers/rtc/rtc-pm8xxx.c
> +++ b/drivers/rtc/rtc-pm8xxx.c
> @@ -1,8 +1,13 @@
>  // SPDX-License-Identifier: GPL-2.0-only
> -/* Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
> +/*
> + * pm8xxx RTC driver
> + *
> + * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
> + * Copyright (c) 2023, Linaro Limited
>   */
>  #include <linux/of.h>
>  #include <linux/module.h>
> +#include <linux/nvmem-consumer.h>
>  #include <linux/init.h>
>  #include <linux/rtc.h>
>  #include <linux/platform_device.h>
> @@ -49,6 +54,8 @@ struct pm8xxx_rtc_regs {
>   * @alarm_irq:		alarm irq number
>   * @regs:		register description
>   * @dev:		device structure
> + * @nvmem_cell:		nvmem cell for offset
> + * @offset:		offset from epoch in seconds
>   */
>  struct pm8xxx_rtc {
>  	struct rtc_device *rtc;
> @@ -57,8 +64,60 @@ struct pm8xxx_rtc {
>  	int alarm_irq;
>  	const struct pm8xxx_rtc_regs *regs;
>  	struct device *dev;
> +	struct nvmem_cell *nvmem_cell;
> +	u32 offset;
>  };
>  
> +static int pm8xxx_rtc_read_nvmem_offset(struct pm8xxx_rtc *rtc_dd)
> +{
> +	size_t len;
> +	void *buf;
> +	int rc;
> +
> +	buf = nvmem_cell_read(rtc_dd->nvmem_cell, &len);
> +	if (IS_ERR(buf)) {
> +		rc = PTR_ERR(buf);
> +		dev_dbg(rtc_dd->dev, "failed to read nvmem offset: %d\n", rc);

Why is dev_dbg() used instead of dev_err() for newly added error
messages?  Also, why do these conditions warrant error logging when some
of the previous patches in this series removed older error logging?

Thanks,
David