Re: [PATCH 1/2] net: designware: eqos: reset phy

On Mon, Jun 07, 2021 at 05:59:02PM +0200, Ahmad Fatoum wrote:

Hello Sascha,

On 07.06.21 16:10, Sascha Hauer wrote:

quoted

The designware eqos DT binding has support for specifying reset GPIOs.
Add support for them.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/net/designware_eqos.c | 33 +++++++++++++++++++++++++++++++++
 drivers/of/of_gpio.c          |  7 +++++++
 2 files changed, 40 insertions(+)

diff --git a/drivers/net/designware_eqos.c b/drivers/net/designware_eqos.c
index d2baaeaf63..0321024169 100644
--- a/drivers/net/designware_eqos.c
+++ b/drivers/net/designware_eqos.c

@@ -8,9 +8,11 @@
 
 #include <common.h>
 #include <init.h>
+#include <gpio.h>
 #include <dma.h>
 #include <net.h>
 #include <of_net.h>
+#include <of_gpio.h>
 #include <linux/iopoll.h>
 #include <linux/time.h>
 #include <linux/sizes.h>

@@ -189,6 +191,33 @@ struct eqos_desc {
 
 #define MII_BUSY		(1 << 0)
 
+static int eqos_phy_reset(struct device_d *dev, struct eqos *eqos)
+{
+	int phy_reset;
+	int ret;
+	u32 delays[3] = { 0, 0, 0 };
+
+	phy_reset = of_get_named_gpio(dev->device_node, "snps,reset-gpio", 0);
+
+        if (!gpio_is_valid(phy_reset))
+		return 0;

Whitespace is wrong.

quoted

+
+	ret = gpio_request(phy_reset, "phy-reset");
+	if (ret)
+		return ret;

Can you use gpiod_get instead? This would reduce the boilerplate here.

Sure. I didn't realize I don't honour the active high/low flags the way
I did it.

quoted

+
+	of_property_read_u32_array(dev->device_node,
+				   "snps,reset-delays-us",
+				   delays, ARRAY_SIZE(delays));
+

Looks strange to read out a delay and not act on it. I'd prefer
waiting delays[0] here.

Yes, it looks strange, but that's because the binding doesn't make much
sense. Why should I insert a delay before doing anything?
I can a delay here, it wouldn't make much difference as all users except
one specify zero delay here anyway. For the one exception I would bet
someone has inserted the first delay without a good reason, they are all
10000.

quoted

+	gpio_direction_active(phy_reset, 0);

This always sets logical zero, because gpio_request above doesn't
accept a flag telling it otherwise. You'll need of_get_named_gpio_flags
here, at which point, you'll have basically open-coded gpiod_get(), so
you could use that.

Right.

quoted

+	udelay(delays[1]);

Linux rounds up to 1 msec granularity here. We should do likewise.

I don't see a good reason for that. The Linux driver used udelay()
initially, that was changed to msleep as the times were too long for
busy waiting. I have no clue why the author didn't use usleep_range
instead.

quoted

+	gpio_set_active(phy_reset, 1);

Nitpick: true/false.

Ok.

Sascha

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