LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Wolfram Sang <wsa@the-dreams.de>
To: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
Cc: Brendan Higgins <brendanhiggins@google.com>,
	Rob Herring <robh+dt@kernel.org>, Joel Stanley <joel@jms.id.au>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Andrew Jeffery <andrew@aj.id.au>,
	linux-i2c@vger.kernel.org, openbmc@lists.ozlabs.org,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-aspeed@lists.ozlabs.org, linux-kernel@vger.kernel.org,
	Jarkko Nikula <jarkko.nikula@linux.intel.com>,
	James Feist <james.feist@linux.intel.com>,
	Vernon Mauery <vernon.mauery@linux.intel.com>
Subject: Re: [PATCH i2c-next v9 5/5] i2c: aspeed: Add bus idle waiting logic for multi-master use cases
Date: Wed, 28 Nov 2018 22:54:40 +0100	[thread overview]
Message-ID: <20181128215434.GA1666@kunai> (raw)
In-Reply-To: <20181030210917.32711-6-jae.hyun.yoo@linux.intel.com>

On Tue, Oct 30, 2018 at 02:09:16PM -0700, Jae Hyun Yoo wrote:
> In multi-master environment, this driver's master cannot know
> exactly when a peer master sends data to this driver's slave so a
> case can be happened that this master tries to send data through
> the master_xfer function but slave data from peer master is still
> being processed by this driver.

So, that I get this correct: your IP core cannot detect a bus busy state
when its own slave address is acessed? Well, I know HW can have bugs,
but I still wonder because a bus is busy as soon as another START has
been detected, independent of which device is going to be accessed.

Even if so, why can't you use a mutex to prevent any master_xfer while
slave_xfer is ongoing?

Shouldn't that be enough according to the above description? Why do you
need the delay? I might be missing something...

> To prevent any state corruption in the case, this patch adds
> checking code if any slave operation is ongoing and it waits up to
> the bus timeout duration before starting a master_xfer operation.
> 
> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
> ---
>  drivers/i2c/busses/i2c-aspeed.c | 55 ++++++++++++++++++++++++---------
>  1 file changed, 40 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index 833b6b6a4c7e..30c3ab3a4844 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -12,6 +12,7 @@
>  
>  #include <linux/clk.h>
>  #include <linux/completion.h>
> +#include <linux/delay.h>
>  #include <linux/err.h>
>  #include <linux/errno.h>
>  #include <linux/i2c.h>
> @@ -115,6 +116,9 @@
>  /* 0x18 : I2CD Slave Device Address Register   */
>  #define ASPEED_I2CD_DEV_ADDR_MASK			GENMASK(6, 0)
>  
> +/* Busy checking */
> +#define ASPEED_I2C_BUS_BUSY_CHECK_INTERVAL_US		(10 * 1000)
> +
>  enum aspeed_i2c_master_state {
>  	ASPEED_I2C_MASTER_INACTIVE,
>  	ASPEED_I2C_MASTER_START,
> @@ -156,6 +160,8 @@ struct aspeed_i2c_bus {
>  	int				cmd_err;
>  	/* Protected only by i2c_lock_bus */
>  	int				master_xfer_result;
> +	/* Multi-master */
> +	bool				multi_master;
>  #if IS_ENABLED(CONFIG_I2C_SLAVE)
>  	struct i2c_client		*slave;
>  	enum aspeed_i2c_slave_state	slave_state;
> @@ -596,27 +602,44 @@ static irqreturn_t aspeed_i2c_bus_irq(int irq, void *dev_id)
>  	return irq_remaining ? IRQ_NONE : IRQ_HANDLED;
>  }
>  
> +static int aspeed_i2c_check_bus_busy(struct aspeed_i2c_bus *bus)
> +{
> +	unsigned long timeout;
> +
> +	if (bus->multi_master) {
> +		might_sleep();
> +		/* Initialize it only when multi_master is set */
> +		timeout = jiffies + bus->adap.timeout;
> +	}
> +
> +	for (;;) {
> +		if (!(readl(bus->base + ASPEED_I2C_CMD_REG) &
> +		      ASPEED_I2CD_BUS_BUSY_STS))
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +			if (bus->slave_state == ASPEED_I2C_SLAVE_STOP)
> +#endif
> +				return 0;
> +		if (!bus->multi_master)
> +			break;
> +		if (time_after(jiffies, timeout))
> +			break;
> +		usleep_range((ASPEED_I2C_BUS_BUSY_CHECK_INTERVAL_US >> 2) + 1,
> +			     ASPEED_I2C_BUS_BUSY_CHECK_INTERVAL_US);
> +	}
> +
> +	return aspeed_i2c_recover_bus(bus);
> +}
> +
>  static int aspeed_i2c_master_xfer(struct i2c_adapter *adap,
>  				  struct i2c_msg *msgs, int num)
>  {
>  	struct aspeed_i2c_bus *bus = i2c_get_adapdata(adap);
>  	unsigned long time_left, flags;
> -	int ret = 0;
>  
> -	spin_lock_irqsave(&bus->lock, flags);
> -	bus->cmd_err = 0;
> -
> -	/* If bus is busy, attempt recovery. We assume a single master
> -	 * environment.
> -	 */
> -	if (readl(bus->base + ASPEED_I2C_CMD_REG) & ASPEED_I2CD_BUS_BUSY_STS) {
> -		spin_unlock_irqrestore(&bus->lock, flags);
> -		ret = aspeed_i2c_recover_bus(bus);
> -		if (ret)
> -			return ret;
> -		spin_lock_irqsave(&bus->lock, flags);
> -	}
> +	if (aspeed_i2c_check_bus_busy(bus))
> +		return -EAGAIN;
>  
> +	spin_lock_irqsave(&bus->lock, flags);
>  	bus->cmd_err = 0;
>  	bus->msgs = msgs;
>  	bus->msgs_index = 0;
> @@ -827,7 +850,9 @@ static int aspeed_i2c_init(struct aspeed_i2c_bus *bus,
>  	if (ret < 0)
>  		return ret;
>  
> -	if (!of_property_read_bool(pdev->dev.of_node, "multi-master"))
> +	if (of_property_read_bool(pdev->dev.of_node, "multi-master"))
> +		bus->multi_master = true;
> +	else
>  		fun_ctrl_reg |= ASPEED_I2CD_MULTI_MASTER_DIS;
>  
>  	/* Enable Master Mode */
> -- 
> 2.19.1
> 

  parent reply	other threads:[~2018-11-28 21:54 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-30 21:09 [PATCH i2c-next v9 0/5] " Jae Hyun Yoo
2018-10-30 21:09 ` [PATCH i2c-next v9 1/5] dt-bindings: i2c: Add 'bus-timeout-ms' and '#retries' properties as common optional Jae Hyun Yoo
2018-11-28 21:54   ` Wolfram Sang
2018-11-28 22:36     ` Jae Hyun Yoo
2018-10-30 21:09 ` [PATCH i2c-next v9 2/5] i2c: core: Add support reading of 'bus-timeout-ms' and '#retries' properties Jae Hyun Yoo
2018-10-30 21:09 ` [PATCH i2c-next v9 3/5] dt-bindings: i2c: aspeed: Add 'bus-timeout-ms' property as an optional property Jae Hyun Yoo
2018-10-30 21:09 ` [PATCH i2c-next v9 4/5] i2c: aspeed: Remove hard-coded bus timeout value setting Jae Hyun Yoo
2018-10-30 21:09 ` [PATCH i2c-next v9 5/5] i2c: aspeed: Add bus idle waiting logic for multi-master use cases Jae Hyun Yoo
     [not found]   ` <201810310601.Odxb7qSY%fengguang.wu@intel.com>
2018-10-30 23:04     ` Jae Hyun Yoo
2018-11-01 17:44   ` kbuild test robot
2018-11-01 18:09     ` Jae Hyun Yoo
2018-11-28 21:54   ` Wolfram Sang [this message]
2018-11-28 22:30     ` Jae Hyun Yoo
2019-01-15 22:47 ` [PATCH i2c-next v9 0/5] " Wolfram Sang
2019-01-15 23:32   ` Jae Hyun Yoo

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181128215434.GA1666@kunai \
    --to=wsa@the-dreams.de \
    --cc=andrew@aj.id.au \
    --cc=benh@kernel.crashing.org \
    --cc=brendanhiggins@google.com \
    --cc=devicetree@vger.kernel.org \
    --cc=jae.hyun.yoo@linux.intel.com \
    --cc=james.feist@linux.intel.com \
    --cc=jarkko.nikula@linux.intel.com \
    --cc=joel@jms.id.au \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-aspeed@lists.ozlabs.org \
    --cc=linux-i2c@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=openbmc@lists.ozlabs.org \
    --cc=robh+dt@kernel.org \
    --cc=vernon.mauery@linux.intel.com \
    --subject='Re: [PATCH i2c-next v9 5/5] i2c: aspeed: Add bus idle waiting logic for multi-master use cases' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).