Re: [PATCH] ARM: davinci: da850 evm: update clock rate for UART 1/2 DT nodes

[Sekhar Nori <nsekhar-l0cyMroinI0@public.gmane.org>]

On 3/15/2013 6:56 PM, Manjunathappa, Prakash wrote:
> Hi Sekhar,
> 
> On Thu, Feb 28, 2013 at 16:09:47, Nori, Sekhar wrote:
>> Prakash,
>>
>> On 2/19/2013 2:02 PM, Manjunathappa, Prakash wrote:
>>> DT kernel with latest of denx SPL U-boot boots with garbled UART
>>> logs. This is because in U-boot UART2 gets sourced by PLL0_SYSCLK2
>>> configured for 150MHz. But later in kernel UART2 gets mapped to
>>> PLL1_SYSCLK2 and is configured for 132MHz not for 150MHz.
>>>
>>> PLL1 is configured for 264MHz to support mDDR on the EVM. That is
>>> memory controller driving mDDR can be configured for 150MHz and
>>> mDDR it self can operate at 132MHz.
>>>
>>> So override UART1 and UART2 DT node clock-frequency property with
>>> rate available on da850 EVM.
>>>
>>> Signed-off-by: Manjunathappa, Prakash <prakash.pm-l0cyMroinI0@public.gmane.org>
>>
>> How about dropping the clock-frequency attribute altogether? of_serial.c
>> seems to be falling back on clk apis if frequency is not passed and that
>> should make the kernel work with all versions of U-Boot.
>>
> 
> Yes it can be dropped by having duplicate clock node for UART having only

You meant an additional clk_lookup entry? That's different from a new
'struct clk' node.

> dev_id. This is required because DT kernel does the clk_get with only dev_id
> and non-DT kernel only with con_id. In DT kernel clk_get is done from generic
> code of_platform_serial_setup:of_serial.c and in non-DT kernel is done from
> platform code, davinci_serial_setup_clk:arch/arm/mach-davinci/serial.c
> 
> Please let me know your opinion on this.

When only one clock is present, con_id of NULL is more appropriate. How
about fixing arch/arm/mach-davinci/serial.c and existing clk_lookup
entries to use this?

Thanks,
Sekhar