Re: [PATCH] drivers: net: fec_imx: Fix system halt after FEC reinit

[Sascha Hauer <sha@pengutronix.de>]

On Tue, Jul 05, 2022 at 10:55:34AM +0200, Anže Lešnik wrote:
> Fix problem with system hang when trying to re-init ethernet interface
> on i.MX devices. The problem is that RX and TX buffer descriptor address
> registers are only being set in fec_probe(). When fec_halt() is called
> when bringing down the interface, this resets the FEC and values are
> lost. As per documentation, these registers should be reconfigured
> before re-enabling the FEC. Additionally, move fec_init() call from
> probe to open, since the FEC needs to re-initialized after every reset.
> 
> Signed-off-by: Anže Lešnik <anze.lesnik@norik.com>
> Link: https://lore.barebox.org/barebox/c51b2c94-61b7-df44-5d4c-025d18c4b24f@norik.com
> ---
>  drivers/net/fec_imx.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)

This patch fixes the hang problem and is otherwise correct, so:

Applied, thanks

It is not the whole story though. The driver will work with a 100M link,
but not with other link speeds. This is because fec_update_linkspeed()
is not called again when fec_open() is called for the second time.

A possible hotfix is to call fec_update_linkspeed() manually from the
driver. Note it has to be called after FEC_ECNTRL is initialized with a
fixed value in fec_open().

Other drivers will have similar problems and this should be fixed at
framework level, so I hesitate to include the hotfix in barebox. Linux
has phy_start() and phy_stop() to be called by the drivers on
open/close. We should probably do the same.

Sascha

-----------------------8<----------------------------

diff --git a/drivers/net/fec_imx.c b/drivers/net/fec_imx.c
index 673555a48a..f2ee211992 100644
--- a/drivers/net/fec_imx.c
+++ b/drivers/net/fec_imx.c
@@ -385,6 +385,9 @@ static int fec_open(struct eth_device *edev)
 		ecr |= 0x100;
 
 	writel(ecr, fec->regs + FEC_ECNTRL);
+
+	fec_update_linkspeed(edev);
+
 	/*
 	 * Enable SmartDMA receive task
 	 */

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