netdev - Re: [PATCH net-next v1 1/4] net: phy: mxl-gpy: add MDINT workaround

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Date:   Fri, 02 Dec 2022 23:53:06 +0100
From:   Michael Walle <michael@...le.cc>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Xu Liang <lxu@...linear.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S . Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v1 1/4] net: phy: mxl-gpy: add MDINT workaround

Am 2022-12-02 19:23, schrieb Andrew Lunn:
> On Fri, Dec 02, 2022 at 04:12:01PM +0100, Michael Walle wrote:
>> At least the GPY215B and GPY215C has a bug where it is still driving 
>> the
>> interrupt line (MDINT) even after the interrupt status register is 
>> read
>> and its bits are cleared. This will cause an interrupt storm.
>> 
>> Although the MDINT is multiplexed with a GPIO pin and theoretically we
>> could switch the pinmux to GPIO input mode, this isn't possible 
>> because
>> the access to this register will stall exactly as long as the 
>> interrupt
>> line is asserted. We exploit this very fact and just read a random
>> internal register in our interrupt handler. This way, it will be 
>> delayed
>> until the external interrupt line is released and an interrupt storm 
>> is
>> avoided.
>> 
>> The internal register access via the mailbox was deduced by looking at
>> the downstream PHY API because the datasheet doesn't mention any of
>> this.
>> 
>> Signed-off-by: Michael Walle <michael@...le.cc>
>> ---
>>  drivers/net/phy/mxl-gpy.c | 83 
>> +++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 83 insertions(+)
>> 
>> diff --git a/drivers/net/phy/mxl-gpy.c b/drivers/net/phy/mxl-gpy.c
>> index 0ff7ef076072..20e610dda891 100644
>> --- a/drivers/net/phy/mxl-gpy.c
>> +++ b/drivers/net/phy/mxl-gpy.c
>> @@ -9,6 +9,7 @@
>>  #include <linux/module.h>
>>  #include <linux/bitfield.h>
>>  #include <linux/hwmon.h>
>> +#include <linux/mutex.h>
>>  #include <linux/phy.h>
>>  #include <linux/polynomial.h>
>>  #include <linux/netdevice.h>
>> @@ -81,6 +82,14 @@
>>  #define VSPEC1_TEMP_STA	0x0E
>>  #define VSPEC1_TEMP_STA_DATA	GENMASK(9, 0)
>> 
>> +/* Mailbox */
>> +#define VSPEC1_MBOX_DATA	0x5
>> +#define VSPEC1_MBOX_ADDRLO	0x6
>> +#define VSPEC1_MBOX_CMD		0x7
>> +#define VSPEC1_MBOX_CMD_ADDRHI	GENMASK(7, 0)
>> +#define VSPEC1_MBOX_CMD_RD	(0 << 8)
>> +#define VSPEC1_MBOX_CMD_READY	BIT(15)
>> +
>>  /* WoL */
>>  #define VPSPEC2_WOL_CTL		0x0E06
>>  #define VPSPEC2_WOL_AD01	0x0E08
>> @@ -88,7 +97,15 @@
>>  #define VPSPEC2_WOL_AD45	0x0E0A
>>  #define WOL_EN			BIT(0)
>> 
>> +/* Internal registers, access via mbox */
>> +#define REG_GPIO0_OUT		0xd3ce00
>> +
>>  struct gpy_priv {
>> +	struct phy_device *phydev;
>> +
>> +	/* serialize mailbox acesses */
>> +	struct mutex mbox_lock;
>> +
> 
>>  static int gpy_probe(struct phy_device *phydev)
>>  {
>>  	struct device *dev = &phydev->mdio.dev;
>> @@ -228,7 +286,9 @@ static int gpy_probe(struct phy_device *phydev)
>>  	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>>  	if (!priv)
>>  		return -ENOMEM;
>> +	priv->phydev = phydev;
> 
> I don't think you use this anywhere. Maybe in one of the following
> patches?

Arg. Yes, it's an leftover from when I was using a workqueue to
reenable the interrupts again.

Any opinion whether this patch should be net or net-next?

-michael