[U-Boot] s3c44b0 serial driver questions

Andrea Scian
2010-06-22T17:11:18Z

Dear Brian,

yes it can be. IIRC I worked only with 75MHz version of S3C44B0, I've
never used a 66MHz one.
Unfortunately I do not have such a board here, neither the time ;-), to
check your bug report..
Did you already check the 66MHz BRD formula?
If it's correct in you testbed to me you can send the patch for commiting

Best Regards,

--

Andrea Scian

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On 21/06/2010 14.45, Brian Cavagnolo wrote:
> Hello,
>
> I'm hoping to use the s3c44b0 serial driver for a CPU with very similar serial
> hardware. One change that I must make is to calculate the baud rate divisor
> with a macro because this operation is board-specific. I propose to clean up
> the large switch statement in the existing code with a macro that calculates
> the BRD using the formula in the datasheet ("S3C44B0X RISC MICROPROCESSOR"
> pg. 10-7; See proposed patch below.) However, the BRD values in the current
> code for the 66MHz case do not match the formula in the data sheet. They are
> all skewed high. Is this a bug?
>
> Ciao,
> Brian
>
> diff --git a/arch/arm/include/asm/arch-s3c44b0/hardware.h
> b/arch/arm/include/asm/arch-s3c44b0/hardware.h
> index 146e265..38ff32c 100644
> --- a/arch/arm/include/asm/arch-s3c44b0/hardware.h
> +++ b/arch/arm/include/asm/arch-s3c44b0/hardware.h
> @@ -11,7 +11,8 @@
> #define REGL(addr) (*(volatile unsigned int *)(REGBASE+addr))
> #define REGW(addr) (*(volatile unsigned short *)(REGBASE+addr))
> #define REGB(addr) (*(volatile unsigned char *)(REGBASE+addr))
> -
> +#define BRD(bps) (DIV_ROUND(CONFIG_S3C44B0_CLOCK_SPEED * 1000000, \
> + (bps)*16) - 1)
>
> /*****************************/
> /* CPU Wrapper Registers */
> diff --git a/drivers/serial/serial_s3c44b0.c b/drivers/serial/serial_s3c44b0.c
> index 95d0266..e6c535c 100644
> --- a/drivers/serial/serial_s3c44b0.c
> +++ b/drivers/serial/serial_s3c44b0.c
> @@ -70,68 +70,7 @@ static int serial_flush_output(void)
>
> void serial_setbrg (void)
> {
> - u32 divisor = 0;
> -
> - /* get correct divisor */
> - switch(gd->baudrate) {
> -
> - case 1200:
> -#if CONFIG_S3C44B0_CLOCK_SPEED==66
> - divisor = 3124;
> -#elif CONFIG_S3C44B0_CLOCK_SPEED==75
> - divisor = 3905;
> -#else
> -# error CONFIG_S3C44B0_CLOCK_SPEED undefined
> -#endif
> - break;
> -
> - case 9600:
> -#if CONFIG_S3C44B0_CLOCK_SPEED==66
> - divisor = 390;
> -#elif CONFIG_S3C44B0_CLOCK_SPEED==75
> - divisor = 487;
> -#else
> -# error CONFIG_S3C44B0_CLOCK_SPEED undefined
> -#endif
> - break;
> -
> - case 19200:
> -#if CONFIG_S3C44B0_CLOCK_SPEED==66
> - divisor = 194;
> -#elif CONFIG_S3C44B0_CLOCK_SPEED==75
> - divisor = 243;
> -#else
> -# error CONFIG_S3C44B0_CLOCK_SPEED undefined
> -#endif
> - break;
> -
> - case 38400:
> -#if CONFIG_S3C44B0_CLOCK_SPEED==66
> - divisor = 97;
> -#elif CONFIG_S3C44B0_CLOCK_SPEED==75
> - divisor = 121;
> -#else
> -# error CONFIG_S3C44B0_CLOCK_SPEED undefined
> -#endif /* break; */
> -
> - case 57600:
> -#if CONFIG_S3C44B0_CLOCK_SPEED==66
> - divisor = 64;
> -#elif CONFIG_S3C44B0_CLOCK_SPEED==75
> - divisor = 80;
> -#else
> -# error CONFIG_S3C44B0_CLOCK_SPEED undefined
> -#endif /* break; */
> -
> - case 115200:
> -#if CONFIG_S3C44B0_CLOCK_SPEED==66
> - divisor = 32;
> -#elif CONFIG_S3C44B0_CLOCK_SPEED==75
> - divisor = 40;
> -#else
> -# error CONFIG_S3C44B0_CLOCK_SPEED undefined
> -#endif /* break; */
> - }
> + u32 divisor = BRD(gd->baudrate);
>
> serial_flush_output();
> serial_flush_input();
>
>