net: stmmac: Add platform level debug register dump feature

dwmac-qcom-ethqos currently exposes a mechanism to dump rgmii registers
after the 'stmmac_dvr_probe()' returns. However with commit
5ec55823 ("net: stmmac: add clocks management for gmac driver"),
we now let 'pm_runtime_put()' disable the clocks before returning from
'stmmac_dvr_probe()'.

This causes a crash when 'rgmii_dump()' register dumps are enabled,
as the clocks are already off.

Since other dwmac drivers (possible future users as well) might
require a similar register dump feature, introduce a platform level
callback to allow the same.

This fixes the crash noticed while enabling rgmii_dump() dumps in
dwmac-qcom-ethqos driver as well. It also allows future changes
to keep a invoking the register dump callback from the correct
place inside 'stmmac_dvr_probe()'.

Fixes: 5ec55823 ("net: stmmac: add clocks management for gmac driver")
Cc: Joakim Zhang <qiangqing.zhang@nxp.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/dwmac-qcom-ethqos.c

@@ -113,8 +113,10 @@ static void rgmii_updatel(struct qcom_ethqos *ethqos,
 	rgmii_writel(ethqos, temp, offset);
 }
 
-static void rgmii_dump(struct qcom_ethqos *ethqos)
+static void rgmii_dump(void *priv)
 {
+	struct qcom_ethqos *ethqos = priv;
+
 	dev_dbg(&ethqos->pdev->dev, "Rgmii register dump\n");
 	dev_dbg(&ethqos->pdev->dev, "RGMII_IO_MACRO_CONFIG: %x\n",
 		rgmii_readl(ethqos, RGMII_IO_MACRO_CONFIG));
@@ -519,6 +521,7 @@ static int qcom_ethqos_probe(struct platform_device *pdev)
 
 	plat_dat->bsp_priv = ethqos;
 	plat_dat->fix_mac_speed = ethqos_fix_mac_speed;
+	plat_dat->dump_debug_regs = rgmii_dump;
 	plat_dat->has_gmac4 = 1;
 	plat_dat->pmt = 1;
 	plat_dat->tso_en = of_property_read_bool(np, "snps,tso");
@@ -527,8 +530,6 @@ static int qcom_ethqos_probe(struct platform_device *pdev)
 	if (ret)
 		goto err_clk;
 
-	rgmii_dump(ethqos);
-
 	return ret;
 
 err_clk:

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -7211,6 +7211,9 @@ int stmmac_dvr_probe(struct device *device,
 	stmmac_init_fs(ndev);
 #endif
 
+	if (priv->plat->dump_debug_regs)
+		priv->plat->dump_debug_regs(priv->plat->bsp_priv);
+
 	/* Let pm_runtime_put() disable the clocks.
 	 * If CONFIG_PM is not enabled, the clocks will stay powered.
 	 */

include/linux/stmmac.h

@@ -233,6 +233,7 @@ struct plat_stmmacenet_data {
 	int (*clks_config)(void *priv, bool enabled);
 	int (*crosststamp)(ktime_t *device, struct system_counterval_t *system,
 			   void *ctx);
+	void (*dump_debug_regs)(void *priv);
 	void *bsp_priv;
 	struct clk *stmmac_clk;
 	struct clk *pclk;