[PATCH 1/3] net: dsa: ksz9477: always toggle reset gpio if available

[Ahmad Fatoum]

On 02.05.24 17:17, Ahmad Fatoum wrote:
> The barebox driver currently only ensures that the switch is out of
> reset, but doesn't actually trigger a reset pulse.
> 
> The Linux driver, on the other hand, holds reset active for 10ms and
> then waits a whopping 100ms after reset deassertion.
> 
> This seems excessive by a thousandfold for at least KSZ9893R[1], whose
> datasheet states:
> 
>   After the de-assertion of reset, it is recommended to wait a minimum of
>   100µs before starting to program the device through any interface.
> 
> Therefore, let's pulse the reset like Linux does and give the switch 100
> microseconds before continuing with the driver probe.
> 
> [1]: DS00002420E-page 176
> 
> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>

I forgot to include the patch prefix, but IMO all three patches are
master material.

Cheers,
Ahmad

> ---
>  drivers/net/ksz9477.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ksz9477.c b/drivers/net/ksz9477.c
> index 1abea9d04017..5c5f4ec8d995 100644
> --- a/drivers/net/ksz9477.c
> +++ b/drivers/net/ksz9477.c
> @@ -433,8 +433,10 @@ static int microchip_switch_probe(struct device *dev)
>  	if (IS_ERR(gpio)) {
>  		dev_warn(dev, "Failed to get 'reset' GPIO (ignored)\n");
>  	} else if (gpio) {
> -		mdelay(1);
> +		gpiod_set_value(gpio, true);
> +		mdelay(10);
>  		gpiod_set_value(gpio, false);
> +		udelay(100);
>  	}
>  
>  	ksz_reset_switch(dev->priv);

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