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Message-ID: <a46eec81-aa2c-74c0-210d-4d28ba46e815@gmail.com>
Date:   Fri, 10 Jun 2022 15:43:15 +0200
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Subject: Re: [PATCH 2/3] tty: serial: atmel: improve clock management
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To:     Claudiu.Beznea@microchip.com, gregkh@linuxfoundation.org,
        jirislaby@kernel.org, Nicolas.Ferre@microchip.com,
        alexandre.belloni@bootlin.com, patrice.chotard@foss.st.com
Cc:     linux-serial@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org
References: <20220525133733.1051714-1-claudiu.beznea@microchip.com>
 <20220525133733.1051714-3-claudiu.beznea@microchip.com>
 <5dae58ca-487a-cbd8-00f8-9951a425f70e@gmail.com>
 <4a189186-9871-09ab-d7e1-9346f7af0bfe@microchip.com>
From:   Richard Genoud <richard.genoud@gmail.com>
In-Reply-To: <4a189186-9871-09ab-d7e1-9346f7af0bfe@microchip.com>
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Hi,
Le 08/06/2022 à 10:18, Claudiu.Beznea@microchip.com a écrit :
> Hi,
> 
> On 02.06.2022 12:29, Richard Genoud wrote:
>>
>> Hi,
>>
>> Le 25/05/2022 à 15:37, Claudiu Beznea a écrit :
>>> atmel_port->clk was requested in atmel_init_port() (which is called only
>>> on probe path) only if atmel_port->clk was NULL. But atmel_port->clk is
>>> NULL on probing path. Thus don't check this. Along with this the clock is
>>> now requested with devm_clk_get() and the clock request has been moved in
>>> atmel_serial_probe() function to avoid disabling/re-enabling it on probe
>>> path for multiple times. All the checks of atmel_port->clk were removed
>>> along with clk_put() and atmel_port->clk = NULL. Now, on probing time the
>>> clock is enabled at the beginning and disabled at the end of probe. As
>>> atmel_console_setup() is called in the middle of probe and clock is
>>> already enabled at that time the clk_prepare_enable() in
>>> atmel_console_setup() has also been removed.
>> Could you split this patch into smaller steps ?
>> I think it will be easier to read and review.
> 
> I kept it as a single patch as it is all related to clock management.
> 
> Having the clock enabled only at the beginning of probe and disabled at the
> end of probe lead to removing the code in atmel_init_port(), also removing
> the code under CONFIG_SERIAL_ATMEL_CONSOLE in probe. Same for the rest of
> the removed code.
> 
> With this, would you still want to split it in multiple patches?

I think that, at least, the switch from clk_get() to devm_clk_get() can 
be in a separate patch.
But in general, I prefer when patches are self-explaining rather than a 
bigger patch with a longer explanation of what it does in the commit 
message.

Regards,
Richard

> 
> Thank you,
> Claudiu Beznea
>>>
>>> Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
>>> ---
>>>    drivers/tty/serial/atmel_serial.c | 65 +++++++------------------------
>>>    1 file changed, 15 insertions(+), 50 deletions(-)
>>>
>>> diff --git a/drivers/tty/serial/atmel_serial.c
>>> b/drivers/tty/serial/atmel_serial.c
>>> index 5c793a23dc54..2955b1012014 100644
>>> --- a/drivers/tty/serial/atmel_serial.c
>>> +++ b/drivers/tty/serial/atmel_serial.c
>>> @@ -2501,24 +2501,7 @@ static int atmel_init_port(struct atmel_uart_port
>>> *atmel_port,
>>>        if (ret)
>>>                return ret;
>>>
>>> -     /* for console, the clock could already be configured */
>>> -     if (!atmel_port->clk) {
>>> -             atmel_port->clk = clk_get(&mpdev->dev, "usart");
>>> -             if (IS_ERR(atmel_port->clk)) {
>>> -                     ret = PTR_ERR(atmel_port->clk);
>>> -                     atmel_port->clk = NULL;
>>> -                     return ret;
>>> -             }
>>> -             ret = clk_prepare_enable(atmel_port->clk);
>>> -             if (ret) {
>>> -                     clk_put(atmel_port->clk);
>>> -                     atmel_port->clk = NULL;
>>> -                     return ret;
>>> -             }
>>> -             port->uartclk = clk_get_rate(atmel_port->clk);
>>> -             clk_disable_unprepare(atmel_port->clk);
>>> -             /* only enable clock when USART is in use */
>>> -     }
>>> +     port->uartclk = clk_get_rate(atmel_port->clk);
>>>
>>>        /*
>>>         * Use TXEMPTY for interrupt when rs485 or ISO7816 else TXRDY or
>>> @@ -2640,10 +2623,6 @@ static int __init atmel_console_setup(struct
>>> console *co, char *options)
>>>                return -ENODEV;
>>>        }
>>>
>>> -     ret = clk_prepare_enable(atmel_ports[co->index].clk);
>>> -     if (ret)
>>> -             return ret;
>>> -
>> Now, "int ret;" is unused, you can remove it.
>>
>>>        atmel_uart_writel(port, ATMEL_US_IDR, -1);
>>>        atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA |
>>> ATMEL_US_RSTRX);
>>>        atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN);
>>> @@ -2889,14 +2868,23 @@ static int atmel_serial_probe(struct
>>> platform_device *pdev)
>>>        atomic_set(&atmel_port->tasklet_shutdown, 0);
>>>        spin_lock_init(&atmel_port->lock_suspended);
>>>
>>> +     atmel_port->clk = devm_clk_get(&pdev->dev, "usart");
>>> +     if (IS_ERR(atmel_port->clk)) {
>>> +             ret = PTR_ERR(atmel_port->clk);
>>> +             goto err;
>>> +     }
>>> +     ret = clk_prepare_enable(atmel_port->clk);
>>> +     if (ret)
>>> +             goto err;
>>> +
>>>        ret = atmel_init_port(atmel_port, pdev);
>>>        if (ret)
>>> -             goto err_clear_bit;
>>> +             goto err_clk_disable_unprepare;
>>>
>>>        atmel_port->gpios = mctrl_gpio_init(&atmel_port->uart, 0);
>>>        if (IS_ERR(atmel_port->gpios)) {
>>>                ret = PTR_ERR(atmel_port->gpios);
>>> -             goto err_clear_bit;
>>> +             goto err_clk_disable_unprepare;
>>>        }
>>>
>>>        if (!atmel_use_pdc_rx(&atmel_port->uart)) {
>>> @@ -2905,7 +2893,7 @@ static int atmel_serial_probe(struct
>>> platform_device *pdev)
>>>                                     sizeof(struct atmel_uart_char),
>>>                                     GFP_KERNEL);
>>>                if (!data)
>>> -                     goto err_alloc_ring;
>>> +                     goto err_clk_disable_unprepare;
>>>                atmel_port->rx_ring.buf = data;
>>>        }
>>>
>>> @@ -2915,26 +2903,9 @@ static int atmel_serial_probe(struct
>>> platform_device *pdev)
>>>        if (ret)
>>>                goto err_add_port;
>>>
>>> -#ifdef CONFIG_SERIAL_ATMEL_CONSOLE
>>> -     if (uart_console(&atmel_port->uart)
>>> -                     && ATMEL_CONSOLE_DEVICE->flags & CON_ENABLED) {
>>> -             /*
>>> -              * The serial core enabled the clock for us, so undo
>>> -              * the clk_prepare_enable() in atmel_console_setup()
>>> -              */
>>> -             clk_disable_unprepare(atmel_port->clk);
>>> -     }
>>> -#endif
>>> -
>>>        device_init_wakeup(&pdev->dev, 1);
>>>        platform_set_drvdata(pdev, atmel_port);
>>>
>>> -     /*
>>> -      * The peripheral clock has been disabled by atmel_init_port():
>>> -      * enable it before accessing I/O registers
>>> -      */
>>> -     clk_prepare_enable(atmel_port->clk);
>>> -
>>>        if (rs485_enabled) {
>>>                atmel_uart_writel(&atmel_port->uart, ATMEL_US_MR,
>>>                                  ATMEL_US_USMODE_NORMAL);
>>> @@ -2958,12 +2929,8 @@ static int atmel_serial_probe(struct
>>> platform_device *pdev)
>>>    err_add_port:
>>>        kfree(atmel_port->rx_ring.buf);
>>>        atmel_port->rx_ring.buf = NULL;
>>> -err_alloc_ring:
>>> -     if (!uart_console(&atmel_port->uart)) {
>>> -             clk_put(atmel_port->clk);
>>> -             atmel_port->clk = NULL;
>>> -     }
>>> -err_clear_bit:
>>> +err_clk_disable_unprepare:
>>> +     clk_disable_unprepare(atmel_port->clk);
>>>        clear_bit(atmel_port->uart.line, atmel_ports_in_use);
>>>    err:
>>>        return ret;
>>> @@ -2997,8 +2964,6 @@ static int atmel_serial_remove(struct
>>> platform_device *pdev)
>>>
>>>        clear_bit(port->line, atmel_ports_in_use);
>>>
>>> -     clk_put(atmel_port->clk);
>>> -     atmel_port->clk = NULL;
>>>        pdev->dev.of_node = NULL;
>>>
>>>        return ret;
>> Thanks !
>>
>> Regards,
>> Richard
>