linux-kernel - Re: [PATCH v2] serial: 8250

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Date:   Mon, 29 May 2017 19:27:38 +0930
From:   Joel Stanley <joel@....id.au>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-serial@...r.kernel.org,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] serial: 8250_of: Add reset support

On Mon, May 29, 2017 at 7:13 PM, Philipp Zabel <p.zabel@...gutronix.de> wrote:
> Hi Joel,
>
> On Fri, 2017-05-26 at 11:55 +1000, Joel Stanley wrote:
>> This adds the hooks for an optional reset controller in the 8250 device
>> tree node.
>>
>> Signed-off-by: Joel Stanley <joel@....id.au>
>>
>> ---
>> v2:
>>  Address Philipp's comments. Thanks for the review!
>>  - use _shared variant
>>  - remove unnecessary error handling
>>
>>  Documentation/devicetree/bindings/serial/8250.txt |  1 +
>>  drivers/tty/serial/8250/8250_of.c                 | 10 ++++++++++
>>  2 files changed, 11 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/serial/8250.txt b/Documentation/devicetree/bindings/serial/8250.txt
>> index 10276a46ecef..63e32393f82b 100644
>> --- a/Documentation/devicetree/bindings/serial/8250.txt
>> +++ b/Documentation/devicetree/bindings/serial/8250.txt
>> @@ -45,6 +45,7 @@ Optional properties:
>>    property.
>>  - tx-threshold: Specify the TX FIFO low water indication for parts with
>>    programmable TX FIFO thresholds.
>> +- resets : phandle + reset specifier pairs
>>
>>  Note:
>>  * fsl,ns16550:
>> diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
>> index 1cbadafc6889..e95cc9698c32 100644
>> --- a/drivers/tty/serial/8250/8250_of.c
>> +++ b/drivers/tty/serial/8250/8250_of.c
>> @@ -19,11 +19,13 @@
>>  #include <linux/of_irq.h>
>>  #include <linux/of_platform.h>
>>  #include <linux/clk.h>
>> +#include <linux/reset.h>
>>
>>  #include "8250.h"
>>
>>  struct of_serial_info {
>>       struct clk *clk;
>> +     struct reset_control *rst;
>>       int type;
>>       int line;
>>  };
>> @@ -132,6 +134,13 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
>>               }
>>       }
>>
>> +     info->rst = devm_reset_control_get_optional_shared(&ofdev->dev, NULL);
>> +     if (IS_ERR(info->rst))
>> +             goto out;
>> +     ret = reset_control_deassert(info->rst);
>> +     if (ret)
>> +             goto out;
>> +
>>       port->type = type;
>>       port->uartclk = clk;
>>       port->flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP
>> @@ -231,6 +240,7 @@ static int of_platform_serial_remove(struct platform_device *ofdev)
>>
>>       if (info->clk)
>>               clk_disable_unprepare(info->clk);
>> +     reset_control_assert(info->rst);
>
> The clock is enabled before the reset is deasserted in
> of_platform_serial_setup, I'd disable it after asserting the reset in
> of_platform_serial_remove. Other than that,
>
> Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>

Doh, I'll send a v3 with your reviewed-by attached.

Thanks!

Joel