[PATCH] i2c: aspeed: Fix i2c bus hang in slave read

[PATCH] i2c: aspeed: Fix i2c bus hang in slave read

[Jian Zhang]

When the `CONFIG_I2C_SLAVE` option is enabled and the device operates
as a slave, a situation arises where the master sends a START signal
without the accompanying STOP signal. This action results in a
persistent I2C bus timeout. The core issue stems from the fact that
the i2c controller remains in a slave read state without a timeout
mechanism. As a consequence, the bus perpetually experiences timeouts.

This proposed patch addresses this problem by introducing a status
check during i2c transmit timeouts. In the event that the controller
is in a slave read state, the i2c controller will be reset to restore
proper functionality and allow the I2C bus to resume normal operation.

Signed-off-by: Jian Zhang <zhangjian.3032@bytedance.com>
---
 drivers/i2c/busses/i2c-aspeed.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index e76befe3f60f..1a95205fc946 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -113,6 +113,7 @@
 		 ASPEED_I2CD_M_RX_CMD |					       \
 		 ASPEED_I2CD_M_TX_CMD |					       \
 		 ASPEED_I2CD_M_START_CMD)
+#define ASPEED_I2CD_SLAVE_CMDS_MASK			GENMASK(31, 29)
 
 /* 0x18 : I2CD Slave Device Address Register   */
 #define ASPEED_I2CD_DEV_ADDR_MASK			GENMASK(6, 0)
@@ -706,6 +707,22 @@ static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
 		     ASPEED_I2CD_BUS_BUSY_STS))
 			aspeed_i2c_recover_bus(bus);
 
+#if IS_ENABLED(CONFIG_I2C_SLAVE)
+		/*
+		 * If master timed out and bus is in slave mode.
+		 * reset the slave mode.
+		 */
+		if (readl(bus->base + ASPEED_I2C_CMD_REG) & ASPEED_I2CD_SLAVE_CMDS_MASK) {
+			spin_lock_irqsave(&bus->lock, flags);
+			u32 func_ctrl_reg_val = readl(bus->base + ASPEED_I2C_FUN_CTRL_REG);
+
+			writel(0, bus->base + ASPEED_I2C_FUN_CTRL_REG);
+			writel(func_ctrl_reg_val, bus->base + ASPEED_I2C_FUN_CTRL_REG);
+			bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
+			spin_unlock_irqrestore(&bus->lock, flags);
+		}
+#endif
+
 		/*
 		 * If timed out and the state is still pending, drop the pending
 		 * master command.
-- 
2.30.2

Re: [PATCH] i2c: aspeed: Fix i2c bus hang in slave read

[Joel Stanley]

On Thu, 10 Aug 2023 at 07:22, Jian Zhang <zhangjian.3032@bytedance.com> wrote:
>
> When the `CONFIG_I2C_SLAVE` option is enabled and the device operates
> as a slave, a situation arises where the master sends a START signal
> without the accompanying STOP signal. This action results in a
> persistent I2C bus timeout. The core issue stems from the fact that
> the i2c controller remains in a slave read state without a timeout
> mechanism. As a consequence, the bus perpetually experiences timeouts.
>
> This proposed patch addresses this problem by introducing a status
> check during i2c transmit timeouts. In the event that the controller
> is in a slave read state, the i2c controller will be reset to restore
> proper functionality and allow the I2C bus to resume normal operation.
>
> Signed-off-by: Jian Zhang <zhangjian.3032@bytedance.com>

Tommy has submitted a similar fix:

 https://lore.kernel.org/linux-i2c/20230906004910.4157305-1-tommy_huang@aspeedtech.com/

His change is very heavy handed; it reinitialises the bus including
re-parsing the device tree (!).

Should we have merged this fix instead? If not, are you able to
confirm that his change fixes your issue?

Cheers,

Joel

> ---
>  drivers/i2c/busses/i2c-aspeed.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index e76befe3f60f..1a95205fc946 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -113,6 +113,7 @@
>                  ASPEED_I2CD_M_RX_CMD |                                        \
>                  ASPEED_I2CD_M_TX_CMD |                                        \
>                  ASPEED_I2CD_M_START_CMD)
> +#define ASPEED_I2CD_SLAVE_CMDS_MASK                    GENMASK(31, 29)
>
>  /* 0x18 : I2CD Slave Device Address Register   */
>  #define ASPEED_I2CD_DEV_ADDR_MASK                      GENMASK(6, 0)
> @@ -706,6 +707,22 @@ static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
>                      ASPEED_I2CD_BUS_BUSY_STS))
>                         aspeed_i2c_recover_bus(bus);
>
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +               /*
> +                * If master timed out and bus is in slave mode.
> +                * reset the slave mode.
> +                */
> +               if (readl(bus->base + ASPEED_I2C_CMD_REG) & ASPEED_I2CD_SLAVE_CMDS_MASK) {
> +                       spin_lock_irqsave(&bus->lock, flags);
> +                       u32 func_ctrl_reg_val = readl(bus->base + ASPEED_I2C_FUN_CTRL_REG);
> +
> +                       writel(0, bus->base + ASPEED_I2C_FUN_CTRL_REG);
> +                       writel(func_ctrl_reg_val, bus->base + ASPEED_I2C_FUN_CTRL_REG);
> +                       bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
> +                       spin_unlock_irqrestore(&bus->lock, flags);
> +               }
> +#endif
> +
>                 /*
>                  * If timed out and the state is still pending, drop the pending
>                  * master command.
> --
> 2.30.2
>

Re: [External] Re: [PATCH] i2c: aspeed: Fix i2c bus hang in slave read

[Jian Zhang]

> From: "Joel Stanley"<joel@jms.id.au>
> Date:  Fri, Sep 22, 2023, 14:48
> Subject:  [External] Re: [PATCH] i2c: aspeed: Fix i2c bus hang in slave read
> To: "Jian Zhang"<zhangjian.3032@bytedance.com>, "Tommy Huang"<tommy_huang@aspeedtech.com>
> Cc: <brendan.higgins@linux.dev>, <benh@kernel.crashing.org>, <andrew@aj.id.au>, <zhangjian3032@gmail.com>, <yulei.sh@bytedance.com>, <xiexinnan@bytedance.com>, "open list:ARM/ASPEED I2C DRIVER"<linux-i2c@vger.kernel.org>, "moderated list:ARM/ASPEED I2C DRIVER"<openbmc@lists.ozlabs.org>, "moderated list:ARM/ASPEED MACHINE SUPPORT"<linux-arm-kernel@lists.infradead.org>, "moderated list:ARM/ASPEED MACHINE SUPPORT"<linux-aspeed@lists.ozlabs.org>, "open list"<linux-kernel@vger.kernel.org>
> On Thu, 10 Aug 2023 at 07:22, Jian Zhang <zhangjian.3032@bytedance.com> wrote:
> >
> > When the `CONFIG_I2C_SLAVE` option is enabled and the device operates
> > as a slave, a situation arises where the master sends a START signal
> > without the accompanying STOP signal. This action results in a
> > persistent I2C bus timeout. The core issue stems from the fact that
> > the i2c controller remains in a slave read state without a timeout
> > mechanism. As a consequence, the bus perpetually experiences timeouts.
> >
> > This proposed patch addresses this problem by introducing a status
> > check during i2c transmit timeouts. In the event that the controller
> > is in a slave read state, the i2c controller will be reset to restore
> > proper functionality and allow the I2C bus to resume normal operation.
> >
> > Signed-off-by: Jian Zhang <zhangjian.3032@bytedance.com>
>
> Tommy has submitted a similar fix:
>
>  https://lore.kernel.org/linux-i2c/20230906004910.4157305-1-tommy_huang@aspeedtech.com/
>
> His change is very heavy handed; it reinitialises the bus including
> re-parsing the device tree (!).
>
> Should we have merged this fix instead? If not, are you able to
> confirm that his change fixes your issue?

I feel it's for solving the same issue, but I think this patch is
missing the action
`bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;`,
 which means it can't resolve my problem. @Tommy, can you help confirm this?

Thanks,

Jian

>
> Cheers,
>
> Joel
>
> > ---
> >  drivers/i2c/busses/i2c-aspeed.c | 17 +++++++++++++++++
> >  1 file changed, 17 insertions(+)
> >
> > diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> > index e76befe3f60f..1a95205fc946 100644
> > --- a/drivers/i2c/busses/i2c-aspeed.c
> > +++ b/drivers/i2c/busses/i2c-aspeed.c
> > @@ -113,6 +113,7 @@
> >                  ASPEED_I2CD_M_RX_CMD |                                        \
> >                  ASPEED_I2CD_M_TX_CMD |                                        \
> >                  ASPEED_I2CD_M_START_CMD)
> > +#define ASPEED_I2CD_SLAVE_CMDS_MASK                    GENMASK(31, 29)
> >
> >  /* 0x18 : I2CD Slave Device Address Register   */
> >  #define ASPEED_I2CD_DEV_ADDR_MASK                      GENMASK(6, 0)
> > @@ -706,6 +707,22 @@ static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
> >                      ASPEED_I2CD_BUS_BUSY_STS))
> >                         aspeed_i2c_recover_bus(bus);
> >
> > +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> > +               /*
> > +                * If master timed out and bus is in slave mode.
> > +                * reset the slave mode.
> > +                */
> > +               if (readl(bus->base + ASPEED_I2C_CMD_REG) & ASPEED_I2CD_SLAVE_CMDS_MASK) {
> > +                       spin_lock_irqsave(&bus->lock, flags);
> > +                       u32 func_ctrl_reg_val = readl(bus->base + ASPEED_I2C_FUN_CTRL_REG);
> > +
> > +                       writel(0, bus->base + ASPEED_I2C_FUN_CTRL_REG);
> > +                       writel(func_ctrl_reg_val, bus->base + ASPEED_I2C_FUN_CTRL_REG);
> > +                       bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
> > +                       spin_unlock_irqrestore(&bus->lock, flags);
> > +               }
> > +#endif
> > +
> >                 /*
> >                  * If timed out and the state is still pending, drop the pending
> >                  * master command.
> > --
> > 2.30.2
> >

Re: [External] Re: [PATCH] i2c: aspeed: Fix i2c bus hang in slave read

[Joel Stanley]

On Fri, 22 Sept 2023 at 14:39, Jian Zhang <zhangjian.3032@bytedance.com> wrote:
> >
> > Tommy has submitted a similar fix:
> >
> >  https://lore.kernel.org/linux-i2c/20230906004910.4157305-1-tommy_huang@aspeedtech.com/
> >
> > His change is very heavy handed; it reinitialises the bus including
> > re-parsing the device tree (!).
> >
> > Should we have merged this fix instead? If not, are you able to
> > confirm that his change fixes your issue?
>
> I feel it's for solving the same issue, but I think this patch is
> missing the action
> `bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;`,
>  which means it can't resolve my problem. @Tommy, can you help confirm this?

You're right, it doesn't change the slave_state at all.

Unfortunately, despite no acks from the maintainers, this patch has
now been merged and backported to stable. We should complete the fix,
or revert it asap.

RE: [External] Re: [PATCH] i2c: aspeed: Fix i2c bus hang in slave read

[Tommy Huang]

Hi Joel / Jian,

	Sorry ~ I didn't observe the last mail from Jian.
	
	My last patch was used to avoid the situation like below link.
	https://lists.ozlabs.org/pipermail/openbmc/2023-August/033756.html

	Because I have applied controller reset in my patch.
	Therefore, I think you just need to reset the slave state by "bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE" in your case.

	BR,

	by Tommy

> -----Original Message-----
> From: Joel Stanley <joel@jms.id.au>
> Sent: Wednesday, September 27, 2023 10:43 AM
> To: Jian Zhang <zhangjian.3032@bytedance.com>
> Cc: Tommy Huang <tommy_huang@aspeedtech.com>;
> brendan.higgins@linux.dev; benh@kernel.crashing.org; andrew@aj.id.au;
> zhangjian3032@gmail.com; yulei.sh@bytedance.com;
> xiexinnan@bytedance.com; open list:ARM/ASPEED I2C DRIVER
> <linux-i2c@vger.kernel.org>; moderated list:ARM/ASPEED I2C DRIVER
> <openbmc@lists.ozlabs.org>; moderated list:ARM/ASPEED MACHINE SUPPORT
> <linux-arm-kernel@lists.infradead.org>; moderated list:ARM/ASPEED
> MACHINE SUPPORT <linux-aspeed@lists.ozlabs.org>; open list
> <linux-kernel@vger.kernel.org>
> Subject: Re: [External] Re: [PATCH] i2c: aspeed: Fix i2c bus hang in slave read
> 
> On Fri, 22 Sept 2023 at 14:39, Jian Zhang <zhangjian.3032@bytedance.com>
> wrote:
> > >
> > > Tommy has submitted a similar fix:
> > >
> > >
> > > https://lore.kernel.org/linux-i2c/20230906004910.4157305-1-tommy_hua
> > > ng@aspeedtech.com/
> > >
> > > His change is very heavy handed; it reinitialises the bus including
> > > re-parsing the device tree (!).
> > >
> > > Should we have merged this fix instead? If not, are you able to
> > > confirm that his change fixes your issue?
> >
> > I feel it's for solving the same issue, but I think this patch is
> > missing the action `bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;`,
> > which means it can't resolve my problem. @Tommy, can you help confirm
> this?
> 
> You're right, it doesn't change the slave_state at all.
> 
> Unfortunately, despite no acks from the maintainers, this patch has now been
> merged and backported to stable. We should complete the fix, or revert it
> asap.

Re: [External] Re: [PATCH] i2c: aspeed: Fix i2c bus hang in slave read

[Wolfram Sang]

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Hi Joel!

> Unfortunately, despite no acks from the maintainers, this patch has
> now been merged and backported to stable.

To explain my reasoning: given the list of unreviewed patches for
aspeed[1], I thought that the driver maintainers were busy or similar.
This happens all the time, so it would be no surprise. Andi is the
driver-comaintainer meanwhile, so an ack from him counts for me as well.

[1] http://patchwork.ozlabs.org/project/linux-i2c/list/?series=&submitter=&state=&q=aspeed&archive=&delegate=

> We should complete the fix, or revert it asap.

Agreed. We can always revert if you guys need more time fixing the issue
properly.

Thanks,

   Wolfram


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