Re: [PATCH v2 1/1] i2c: designware: Fix wrong setting for {ss,fs,hs}_{h,l}cnt registers

[Jarkko Nikula <jarkko.nikula@linux.intel.com>]

On 8/2/24 4:01 PM, Adrian Huang wrote:
> From: Adrian Huang <ahuang12@lenovo.com>
> 
> When disabling CONFIG_X86_AMD_PLATFORM_DEVICE option, the driver
> 'drivers/acpi/acpi_apd.c' won't be compiled. This leads to a situation
> where BMC (Baseboard Management Controller) cannot retrieve the memory
> temperature via the i2c interface after i2c DW driver is loaded. Note
> that BMC can retrieve the memory temperature before booting into OS.
> 
> [Debugging Detail]
>    1. dev->pclk and dev->clk are NULL when calling devm_clk_get_optional()
>       in dw_i2c_plat_probe().
> 
>    2. The callings of i2c_dw_scl_hcnt() in i2c_dw_set_timings_master()
>       return 65528 (-8 in integer format) or 65533 (-3 in integer format).
>       The following log shows SS's HCNT/LCNT:
> 
>         i2c_designware AMDI0010:01: Standard Mode HCNT:LCNT = 65533:65535
> 
>    3. The callings of i2c_dw_scl_lcnt() in i2c_dw_set_timings_master()
>       return 65535 (-1 in integer format). The following log shows SS's
>       HCNT/LCNT:
> 
>         i2c_designware AMDI0010:01: Fast Mode HCNT:LCNT = 65533:65535
> 
>    4. i2c_dw_init_master() configures the register IC_SS_SCL_HCNT with
>       the value 65533. However, the DW i2c databook mentioned the value
>       cannot be higher than 65525. Quote from the DW i2c databook:
> 
>         NOTE: This register must not be programmed to a value higher than
>               65525, because DW_apb_i2c uses a 16-bit counter to flag an
>               I2C bus idle condition when this counter reaches a value of
>               IC_SS_SCL_HCNT + 10.
> 
>    5. Since ss_hcnt, ss_lcnt, fs_hcnt, and fs_lcnt are the invalid
>       values, we should not write the corresponding registers.
> 
> Fix the issue by reading dev->{ss,fs,hs}_hcnt and dev->{ss,fs,hs}_lcnt
> from HW registers if ic_clk is not set.
> 
> Link: https://lore.kernel.org/linux-i2c/8295cbe1-a7c5-4a35-a189-5d0bff51ede6@linux.intel.com/
> Suggested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
> Signed-off-by: Adrian Huang <ahuang12@lenovo.com>
> Reported-by: Dong Wang <wangdong28@lenovo.com>
> Tested-by: Dong Wang <wangdong28@lenovo.com>
> 
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>