[i2c-next,v3,2/3] i2c: aspeed: Add 'aspeed, timeout' DT property reading code

This commit adds reading code of the 'aspeed,timeout' DT property
to set 'timeout' value in adapter configuration. This value still
case be configured through an I2C_TIMEOUT ioctl on cdev too.

Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
---
 drivers/i2c/busses/i2c-aspeed.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

On Thu, 27 Sep 2018 at 01:58, Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com> wrote:
>
> This commit adds reading code of the 'aspeed,timeout' DT property
> to set 'timeout' value in adapter configuration. This value still
> case be configured through an I2C_TIMEOUT ioctl on cdev too.
>
> Signed-off-by: Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com>
> ---
>  drivers/i2c/busses/i2c-aspeed.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
> index 8dc9161ced38..0d934ce0c028 100644
> --- a/drivers/i2c/busses/i2c-aspeed.c
> +++ b/drivers/i2c/busses/i2c-aspeed.c
> @@ -115,6 +115,9 @@
>  /* 0x18 : I2CD Slave Device Address Register   */
>  #define ASPEED_I2CD_DEV_ADDR_MASK                      GENMASK(6, 0)
>
> +/* Timeout */
> +#define ASPEED_I2C_BUS_TIMEOUT_US_DEFAULT              (5 * 1000 * 1000)

The 5 seconds time out is way too long. On a system that doesn't have
functional i2c, this holds up boot for a long time as most i2c client
drivers try to initialise their device and fail. I realise you're not
changing the value, but we should pick a better default. 1 second?
Half a second?

> +
>  enum aspeed_i2c_master_state {
>         ASPEED_I2C_MASTER_INACTIVE,
>         ASPEED_I2C_MASTER_START,
> @@ -885,6 +888,7 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
>         struct clk *parent_clk;
>         struct resource *res;
>         int irq, ret;
> +       u32 timeout_us;
>
>         bus = devm_kzalloc(&pdev->dev, sizeof(*bus), GFP_KERNEL);
>         if (!bus)
> @@ -918,6 +922,11 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
>                 bus->bus_frequency = 100000;
>         }
>
> +       ret = of_property_read_u32(pdev->dev.of_node, "aspeed,timeout",
> +                                  &timeout_us);

Can we make this binding generic? It's not specific to aspeed's
hardware. Getting the value could even part of the i2c core.

I read the previous thread with Wolfram. I think this would still fit
with what Wolfram suggested, but please forgive my jetlagged brain if
I've missed something.

Cheers,

Joel
> +       if (ret)
> +               timeout_us = ASPEED_I2C_BUS_TIMEOUT_US_DEFAULT;
> +
>         match = of_match_node(aspeed_i2c_bus_of_table, pdev->dev.of_node);
>         if (!match)
>                 bus->get_clk_reg_val = aspeed_i2c_24xx_get_clk_reg_val;
> @@ -930,7 +939,7 @@ static int aspeed_i2c_probe_bus(struct platform_device *pdev)
>         init_completion(&bus->cmd_complete);
>         bus->adap.owner = THIS_MODULE;
>         bus->adap.retries = 0;
> -       bus->adap.timeout = 5 * HZ;
> +       bus->adap.timeout = usecs_to_jiffies(timeout_us);
>         bus->adap.algo = &aspeed_i2c_algo;
>         bus->adap.dev.parent = &pdev->dev;
>         bus->adap.dev.of_node = pdev->dev.of_node;
> --
> 2.19.0
>

Hi Joel,

On 9/26/2018 8:11 PM, Joel Stanley wrote:
> On Thu, 27 Sep 2018 at 01:58, Jae Hyun Yoo <jae.hyun.yoo@linux.intel.com> wrote:
>>
>> +/* Timeout */
>> +#define ASPEED_I2C_BUS_TIMEOUT_US_DEFAULT              (5 * 1000 * 1000)
> 
> The 5 seconds time out is way too long. On a system that doesn't have
> functional i2c, this holds up boot for a long time as most i2c client
> drivers try to initialise their device and fail. I realise you're not
> changing the value, but we should pick a better default. 1 second?
> Half a second?
> 

I agree with you. We could probably use 1 second as default which can
cover the most of general cases. If so, we don't need to make the
default setting in this driver because i2c-core-base will default
adap->timeout to 1 second if the value is 0 when a driver registers an
adapter. Will fix this code.

>>
>> +       ret = of_property_read_u32(pdev->dev.of_node, "aspeed,timeout",
>> +                                  &timeout_us);
> 
> Can we make this binding generic? It's not specific to aspeed's
> hardware. Getting the value could even part of the i2c core.
> 
> I read the previous thread with Wolfram. I think this would still fit
> with what Wolfram suggested, but please forgive my jetlagged brain if
> I've missed something.
> 

It followed the way of the existing i2c-mpc driver uses 'fsl,timeout'
for the same purpose. Though, I also want to make it as a generic as you
suggested like 'timeout' in milliseconds unit, not in microseconds unit.
If making it a generic property is acceptable, I'll fix it too.

Wolfram, can you please share your thought on it?

Thanks,
Jae