[PATCH v4 06/14] net: dwc_eth_qos: Set DMA_MODE SWR bit to reset the MAC

[Marek Vasut <marex@denx.de>]

The driver currently only waits for DMA_MODE SWR bit to clear itself.
This is insufficient e.g. on i.MX8M Plus, where the MAC must be reset
before IOMUX GPR[1] content is latched into the MAC and used. Without
the proper reset, the i.MX8M Plus MAC variant does not take the value
in IOMUX GPR[1] into account, which makes it impossible e.g. to switch
interface mode from RGMII to any other.

Since proper reset is desired in general to put the block into defined
state, always assert the DMA_MODE SWR bit before waiting for the bit
to clear itself.

Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
Signed-off-by: Marek Vasut <marex@denx.de>
---
Cc: "Ariel D'Alessandro" <ariel.dalessandro@collabora.com>
Cc: "NXP i.MX U-Boot Team" <uboot-imx@nxp.com>
Cc: Andrey Zhizhikin <andrey.zhizhikin@leica-geosystems.com>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: Joe Hershberger <joe.hershberger@ni.com>
Cc: Lukasz Majewski <lukma@denx.de>
Cc: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Michael Trimarchi <michael@amarulasolutions.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Ramon Fried <rfried.dev@gmail.com>
Cc: Sean Anderson <seanga2@gmail.com>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Tim Harvey <tharvey@gateworks.com>
Cc: Tommaso Merciai <tommaso.merciai@amarulasolutions.com>
Cc: u-boot@lists.denx.de
---
V2: Add RB from Ramon
V3: No change
V4: No change
---
 drivers/net/dwc_eth_qos.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/dwc_eth_qos.c b/drivers/net/dwc_eth_qos.c
index 9a5575e7b83..ec58697b311 100644
--- a/drivers/net/dwc_eth_qos.c
+++ b/drivers/net/dwc_eth_qos.c
@@ -761,6 +761,12 @@ static int eqos_start(struct udevice *dev)
 
 	eqos->reg_access_ok = true;
 
+	/*
+	 * Assert the SWR first, the actually reset the MAC and to latch in
+	 * e.g. i.MX8M Plus GPR[1] content, which selects interface mode.
+	 */
+	setbits_le32(&eqos->dma_regs->mode, EQOS_DMA_MODE_SWR);
+
 	ret = wait_for_bit_le32(&eqos->dma_regs->mode,
 				EQOS_DMA_MODE_SWR, false,
 				eqos->config->swr_wait, false);
-- 
2.39.2