Date:   Fri, 11 Feb 2022 15:49:03 -0500
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     Hugo Villeneuve <hugo@...ovil.com>
Cc:     hvilleneuve@...onoff.com, a.zummo@...ertech.it,
        alexandre.belloni@...tlin.com, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 00/14] rtc: pcf2127: add PCF2131 driver

On Fri, 11 Feb 2022 15:35:06 -0500
Hugo Villeneuve <hugo@...ovil.com> wrote:

> From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> 
> Hello,
> this patch series adds the driver for the PCF2131 real-time clock.

Hi,
sorry, I forgot to add the V2 prefix to all the patches in this serie. Please ignore them, I will resend them with the proper [PATCH v2...] prefix.

Hugo.


> This RTC is very similar in functionality to the PCF2127/29 with the
> following differences:
>   -supports two new control registers at offsets 4 and 5
>   -supports a new reset register
>   -supports 4 tamper detection functions instead of 1
>   -has no nvmem (like the PCF2129)
>   -has two output interrupt pins instead of one
>   -has 1/100th seconds capabilities (not supported in this driver)
>   -pcf2127 has watchdog clock sources: 1/60,   1, 64 and 4096Hz
>    pcf2131 has watchdog clock sources: 1/64, 1/4,  4 and   64Hz
>   -watchdog value register cannot be read after being set
> 
> Most of the register addresses are very different, although they still
> follow the same layout. For example, the time/date and tamper registers
> have a different base address, but the offsets are all the same.
> Consequently, the source code of the PCF2127 driver can be easily adapted
> to support this new device.
> 
> This patch series need the following patch to be applied first:
> [PATCH] rtc: pcf2127: fix bug when reading alarm registers
> Link: https://patchwork.ozlabs.org/project/rtc-linux/patch/20220208162908.3182581-1-hugo@hugovil.com/
> 
> Patches 1 to 6 modify the existing pcf2127 driver to make it more generic
> and able to support multiple variants, like the PCF2131. This is done
> mostly by using offsets instead of absolute hardcoded register addresses.
> 
> Patch 7 add actual support for the PCF2131.
> 
> Patch 8 configures all interrupt sources to go through the INT A pin.
> 
> Patch 9 changes the PWRMNG bits to be the same with the PCF2131 as they
>       are with the PCF2127/29 (different default values).
> 
> Patch 10 allow to confirm PCF2131 device presence by reading the reset
>       register fixed pattern.
> 
> Patch 11 adapt the time/date registers write sequence for PCF2131 (STOP and
>       CPR bits).
> 
> Patch 12 add support for generic watchdog timing configuration.
> 
> Patch 13 add a new flag to identify if device has read support for reading
>       watchdog register value.
>       Since the watchdog value register cannot be read on the PCF2131 after
>       being set, it seems that we cannot detect if watchdog timer was
>       started by bootloader. I am not sure what is the best way to handle
>       this situation, suggestions are welcomed.
> 
> Patch 14 add the dt-bindings for the PCF2131.
> 
> I have tested the driver using a PCF2131-ARD evaluation board connected to
> an NXP imx8mp evaluation board:
>   - Time get/set ok;
>   - Alarms get/set ok
>   - Timestamp 1 to 4 ok
>   - IRQ alarm ok
>   - Watchdog ok
>   - Also tested successfully with "RTC Driver Test Example" from
>     Documentation/rtc.txt
> 
> I have not tested the driver on PCF2127 or PCF2129 hardware as I do not
> have either one of these devices. However, I compared the registers
> read/write access addresses and values before and after modifying the
> driver by simulating I2C read and writes for some operations (probe, read
> time), and they are the same (apart from new read/writes for all variants).
> 
> Thank you.
> 
> Link: [v1] https://patchwork.ozlabs.org/project/rtc-linux/patch/20220125200009.900660-2-hugo@hugovil.com/
> 
> Changes for V2:
> - Add cover letter (in V1, was mailed only to my email address, and not
>   to RTC mailing list and maintainers)
> - In general, fix and improvements after I have tested on real hardware
> - Fix alarm interrupt A/B mask setting for PCF2131:
>   PCF2131_BIT_INT_AIE must be cleared, not set, to enable interrupt.
> - Remove low_reg validation: only check if TS interrupt flag is
>   defined, as low_reg is defined at address 0 for PCF2127/29.
> - Change PWRMNG value for PCF2131: default is different than PCF2127/29.
> - Adapt time/date registers write sequence for PCF2131 (STOP and CPR bits).
> - Map all interrupt sources to INT A pin
> - Read and validate PCF2131 device presence from RESET register
> - Adapt watchdog configuration for PCF2131
> 
> Hugo Villeneuve (14):
>   rtc: pcf2127: add variant-specific configuration structure
>   rtc: pcf2127: adapt for time/date registers at any offset
>   rtc: pcf2127: adapt for alarm registers at any offset
>   rtc: pcf2127: adapt for WD registers at any offset
>   rtc: pcf2127: adapt for CLKOUT register at any offset
>   rtc: pcf2127: add support for multiple TS functions
>   rtc: pcf2127: add support for PCF2131 RTC
>   rtc: pcf2127: add support for PCF2131 interrupts on output INT_A
>   rtc: pcf2127: set PWRMNG value for PCF2131
>   rtc: pcf2127: read and validate PCF2131 device signature
>   rtc: pcf2127: adapt time/date registers write sequence for PCF2131
>   rtc: pcf2127: support generic watchdog timing configuration
>   rtc: pcf2127: add flag for watchdog register value read support
>   dt-bindings: rtc: pcf2127: add PCF2131
> 
>  .../devicetree/bindings/rtc/nxp,pcf2127.yaml  |  19 +-
>  drivers/rtc/Kconfig                           |   4 +-
>  drivers/rtc/rtc-pcf2127.c                     | 940 ++++++++++++++----
>  3 files changed, 769 insertions(+), 194 deletions(-)
> 
> -- 
> 2.30.2
> 
> 


-- 
Hugo Villeneuve <hugo@...ovil.com>

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