linux-kernel - Re: [PATCH 1/2] i2c: exynos5: add support for HSI2C on Exynos5260 SoC

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Date:	Fri, 22 Nov 2013 13:02:22 +0530
From:	Naveen Krishna Ch <naveenkrishna.ch@...il.com>
To:	Yuvaraj Cd <yuvaraj.lkml@...il.com>
Cc:	Naveen Krishna Chatradhi <ch.naveen@...sung.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	hs@...x.de, khali@...ux-fr.org, Ben Dooks <ben-linux@...ff.org>
Subject: Re: [PATCH 1/2] i2c: exynos5: add support for HSI2C on Exynos5260 SoC

Hello Yuvaraj,

On 22 November 2013 12:16, Yuvaraj Cd <yuvaraj.lkml@...il.com> wrote:
> On Fri, Nov 22, 2013 at 11:42 AM, Naveen Krishna Chatradhi
> <ch.naveen@...sung.com> wrote:
>> This patch adds new compatible to support HSI2C module on Exynos5260
>> HSI2C module on Exynos5260 needs to be reset during during initialization.
>>
>> Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@...sung.com>
>> ---
>>  .../devicetree/bindings/i2c/i2c-exynos5.txt        |    6 +++-
>>  drivers/i2c/busses/i2c-exynos5.c                   |   31 ++++++++++++++++++--
>>  2 files changed, 34 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/i2c/i2c-exynos5.txt b/Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
>> index 056732c..704ab92 100644
>> --- a/Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
>> +++ b/Documentation/devicetree/bindings/i2c/i2c-exynos5.txt
>> @@ -5,7 +5,11 @@ at various speeds ranging from 100khz to 3.4Mhz.
>>
>>  Required properties:
>>    - compatible: value should be.
>> -      -> "samsung,exynos5-hsi2c", for i2c compatible with exynos5 hsi2c.
>> +       -> "samsung,exynos5-hsi2c", for i2c compatible with HSI2C available on
>> +                               Exynos5250/5420 SoCs.
>> +       -> "samsung,exynos5260-hsi2c", for i2c compatible with HSI2C available
>> +                               on Exynos5260 SoCs.
>> +
>>    - reg: physical base address of the controller and length of memory mapped
>>      region.
>>    - interrupts: interrupt number to the cpu.
>> diff --git a/drivers/i2c/busses/i2c-exynos5.c b/drivers/i2c/busses/i2c-exynos5.c
>> index aca3991..cbb49e2 100644
>> --- a/drivers/i2c/busses/i2c-exynos5.c
>> +++ b/drivers/i2c/busses/i2c-exynos5.c
>> @@ -184,14 +184,35 @@ struct exynos5_i2c {
>>          * 2. Fast speed upto 1Mbps
>>          */
>>         int                     speed_mode;
>> +
>> +       /* Version of HS-I2C Hardware */
>> +       unsigned int            version;
>> +};
>> +
>> +enum hsi2c_version {
>> +       EXYNOS_5,
>> +       EXYNOS_5260
>>  };
>>
>>  static const struct of_device_id exynos5_i2c_match[] = {
>> -       { .compatible = "samsung,exynos5-hsi2c" },
>> +       {
>> +               .compatible = "samsung,exynos5-hsi2c",
>> +               .data = (void *)EXYNOS_5 },
>> +       {
>> +               .compatible = "samsung,exynos5260-hsi2c",
>> +               .data = (void *)EXYNOS_5260 },
>>         {},
>>  };
>>  MODULE_DEVICE_TABLE(of, exynos5_i2c_match);
>>
>> +static inline unsigned int exynos5_i2c_get_version(struct platform_device *pdev)
>> +{
>> +       const struct of_device_id *match;
>> +
>> +       match = of_match_node(exynos5_i2c_match, pdev->dev.of_node);
>> +       return (unsigned int)match->data;
>> +}
>> +
>>  static void exynos5_i2c_clr_pend_irq(struct exynos5_i2c *i2c)
>>  {
>>         writel(readl(i2c->regs + HSI2C_INT_STATUS),
>> @@ -692,7 +713,13 @@ static int exynos5_i2c_probe(struct platform_device *pdev)
>>         if (ret)
>>                 goto err_clk;
>>
>> -       exynos5_i2c_init(i2c);
>> +       i2c->version = exynos5_i2c_get_version(pdev);
>> +
>> +       /* The HS-I2C core on Exynos5260 needs a reset to start with */
>> +       if (i2c->version == EXYNOS_5260)
>
> Is there is any change in the HSI2C IP for EXYNOS5260?
> Can you let me know whats the change w.r.t IP and
> why it needs reset to start,which was not needed in earlier SOC?

Problem:
While working on HSI2C on uboot for Exynos5260 i faced a problem.
To operate on bus "0" which was default bus
If i try i2c md/mw on channel 0 without selecting the bus using "i2c dev 0"
the transaction was failing. But, the subsequent transactions were passing.

Software Work around:
After looking at the code i found out, resetting the bus for the first
time made it work.

Hardware engg suggestion:
Meanwhile inputs from Hardware engineers are, "HSI2C on Exynos5260 needs a reset
during init."  I've not gone personally into the internals of HSI2C module.

>From user manual for Exynos5260, FIFO depth supported is 16bytes
instead of 64bytes.
>
>> +               exynos5_i2c_reset(i2c);
>> +       else
>> +               exynos5_i2c_init(i2c);
>>
>>         ret = i2c_add_adapter(&i2c->adap);
>>         if (ret < 0) {
>> --
>> 1.7.10.4
>>
>> --
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