netdev - Re: [PATCH net-next] net: dsa: lan9303: ensure chip reset and wait for READY status

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Message-ID: <aafbddb5-c9d4-46b4-a5f2-0f56c58fc5df@microchip.com>
Date: Tue, 1 Oct 2024 11:30:24 +0000
From: <Parthiban.Veerasooran@...rochip.com>
To: <alexander.sverdlin@...mens.com>, <netdev@...r.kernel.org>
CC: <agust@...x.de>, <andrew@...n.ch>, <f.fainelli@...il.com>,
	<olteanv@...il.com>
Subject: Re: [PATCH net-next] net: dsa: lan9303: ensure chip reset and wait
 for READY status

Hi,

I think the subject line should have "net" tag instead of "net-next" as 
it is an update on the existing driver in the netdev source tree.

https://www.kernel.org/doc/Documentation/networking/netdev-FAQ.txt

Best regards,
Parthiban V

On 01/10/24 2:31 pm, A. Sverdlin wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> From: Anatolij Gustschin <agust@...x.de>
> 
> Accessing device registers seems to be not reliable, the chip
> revision is sometimes detected wrongly (0 instead of expected 1).
> 
> Ensure that the chip reset is performed via reset GPIO and then
> wait for 'Device Ready' status in HW_CFG register before doing
> any register initializations.
> 
> Signed-off-by: Anatolij Gustschin <agust@...x.de>
> [alex: added msleep() + justification for tout]
> Signed-off-by: Alexander Sverdlin <alexander.sverdlin@...mens.com>
> ---
>   drivers/net/dsa/lan9303-core.c | 38 ++++++++++++++++++++++++++++++++++
>   1 file changed, 38 insertions(+)
> 
> diff --git a/drivers/net/dsa/lan9303-core.c b/drivers/net/dsa/lan9303-core.c
> index 268949939636a..5744e7ac436fb 100644
> --- a/drivers/net/dsa/lan9303-core.c
> +++ b/drivers/net/dsa/lan9303-core.c
> @@ -839,6 +839,8 @@ static void lan9303_handle_reset(struct lan9303 *chip)
>          if (!chip->reset_gpio)
>                  return;
> 
> +       gpiod_set_value_cansleep(chip->reset_gpio, 1);
> +
>          if (chip->reset_duration != 0)
>                  msleep(chip->reset_duration);
> 
> @@ -863,9 +865,45 @@ static int lan9303_disable_processing(struct lan9303 *chip)
> 
>   static int lan9303_check_device(struct lan9303 *chip)
>   {
> +       /*
> +        * Loading of the largest supported EEPROM is expected to take at least
> +        * 5.9s
> +        */
> +       int tout = 6000 / 30;
>          int ret;
>          u32 reg;
> 
> +       do {
> +               ret = lan9303_read(chip->regmap, LAN9303_HW_CFG, &reg);
> +               if (ret) {
> +                       dev_err(chip->dev, "failed to read HW_CFG reg: %d\n",
> +                               ret);
> +               }
> +               tout--;
> +
> +               dev_dbg(chip->dev, "%s: HW_CFG: 0x%08x\n", __func__, reg);
> +               if ((reg & LAN9303_HW_CFG_READY) || !tout)
> +                       break;
> +
> +               /*
> +                * In I2C-managed configurations this polling loop will clash
> +                * with switch's reading of EEPROM right after reset and this
> +                * behaviour is not configurable. While lan9303_read() already
> +                * has quite long retry timeout, seems not all cases are being
> +                * detected as arbitration error.
> +                *
> +                * According to datasheet, EEPROM loader has 30ms timeout
> +                * (in case of missing EEPROM).
> +                */
> +               msleep(30);
> +       } while (true);
> +
> +       if (!tout) {
> +               dev_err(chip->dev, "%s: HW_CFG not ready: 0x%08x\n",
> +                       __func__, reg);
> +               return -ENODEV;
> +       }
> +
>          ret = lan9303_read(chip->regmap, LAN9303_CHIP_REV, &reg);
>          if (ret) {
>                  dev_err(chip->dev, "failed to read chip revision register: %d\n",
> --
> 2.46.0
> 
>