Re: [PATCH v3 1/2] serial: zynqmp: Fetch baudrate from dtb and update

Hi Venkatesh,

On Tue, 25 Apr 2023 at 06:05, Venkatesh Yadav Abbarapu venkatesh.abbarapu@amd.com wrote:

From: Algapally Santosh Sagar santoshsagar.algapally@amd.com

The baudrate configured in .config is taken by default by serial. If change of baudrate is required then the .config needs to changed and u-boot recompilation is required or the u-boot environment needs to be updated.

To avoid this, support is added to fetch the baudrate directly from the device tree file and update. The serial, prints the log with the configured baudrate in the dtb. The commit c4df0f6f315c ("arm: mvebu: Espressobin: Set default value for $fdtfile env variable") is taken as reference for changing the default environment variable.

The default environment stores the default baudrate value, When default baudrate and dtb baudrate are not same glitches are seen on the serial. So, the environment also needs to be updated with the dtb baudrate to avoid the glitches on the serial.

Signed-off-by: Algapally Santosh Sagar santoshsagar.algapally@amd.com Signed-off-by: Venkatesh Yadav Abbarapu venkatesh.abbarapu@amd.com

---

drivers/serial/serial-uclass.c | 32 +++++++++++++++++++++++++++ include/env_default.h | 7 ++++-- include/env_internal.h | 2 +- include/fdtdec.h | 8 +++++++ include/serial.h | 1 + lib/fdtdec.c | 40 ++++++++++++++++++++++++++++++++++ 6 files changed, 87 insertions(+), 3 deletions(-)

Can you please add something to doc/ for this feature?

diff --git a/drivers/serial/serial-uclass.c b/drivers/serial/serial-uclass.c index 067fae2614..d77d3bda36 100644 --- a/drivers/serial/serial-uclass.c +++ b/drivers/serial/serial-uclass.c @@ -154,12 +154,44 @@ static void serial_find_console_or_panic(void) } #endif /* CONFIG_SERIAL_PRESENT */

+#ifdef CONFIG_SERIAL_DT_BAUD

Please drop this #ifdef

+int serial_get_valid_baudrate(int baud) +{

•   int i;
  

•   for (i = 0; i < ARRAY_SIZE(baudrate_table); ++i) {
  

•           if (baud == baudrate_table[i])
  

•                   return 0;
  

•   }
  

•   return -EINVAL;
  

+} +#endif

/* Called prior to relocation */ int serial_init(void) { #if CONFIG_IS_ENABLED(SERIAL_PRESENT) serial_find_console_or_panic(); gd->flags |= GD_FLG_SERIAL_READY; +#ifdef CONFIG_SERIAL_DT_BAUD

if (IS_ENABLED(CONFIG_SERIAL_DT_BAUD)

You also should add a Kconfig option. I suggest naming it OF_SERIAL_BOARD since we typically put an OF_ prefix on such options.

•   int ret = 0;
  

•   char *ptr = &default_environment[0];
  

•   /*
  

•    * Fetch the baudrate from the dtb and update the value in the
  

•    * default environment.
  

•    */
  

•   ret = fdtdec_get_baud_from_dtb(gd->fdt_blob);
  

•   if (ret != -EINVAL && ret != -EFAULT) {
  

•           gd->baudrate = ret;
  

•           while (*ptr != '\0' && *(ptr + 1) != '\0')
  

•                   ptr++;
  

•           ptr += 2;
  

•           sprintf(ptr, "baudrate=%d", gd->baudrate);
  

•   }
  

+#endif serial_setbrg(); #endif

diff --git a/include/env_default.h b/include/env_default.h index c0df39d62f..4f286ffc9e 100644 --- a/include/env_default.h +++ b/include/env_default.h @@ -23,7 +23,7 @@ env_t embedded_environment __UBOOT_ENV_SECTION__(environment) = { { #elif defined(DEFAULT_ENV_INSTANCE_STATIC) static char default_environment[] = { -#elif defined(DEFAULT_ENV_IS_RW) +#elif defined(CONFIG_DEFAULT_ENV_IS_RW) char default_environment[] = { #else const char default_environment[] = { @@ -44,7 +44,7 @@ const char default_environment[] = { #if defined(CONFIG_BOOTDELAY) "bootdelay=" __stringify(CONFIG_BOOTDELAY) "\0" #endif -#if defined(CONFIG_BAUDRATE) && (CONFIG_BAUDRATE >= 0) +#if !defined(CONFIG_SERIAL_DT_BAUD) && defined(CONFIG_BAUDRATE) && (CONFIG_BAUDRATE >= 0) "baudrate=" __stringify(CONFIG_BAUDRATE) "\0" #endif #ifdef CONFIG_LOADS_ECHO @@ -120,6 +120,9 @@ const char default_environment[] = { #endif #ifdef CFG_EXTRA_ENV_SETTINGS CFG_EXTRA_ENV_SETTINGS +#endif +#ifdef CONFIG_SERIAL_DT_BAUD

•   "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
  

What is this for?

#endif "\0" #else /* CONFIG_USE_DEFAULT_ENV_FILE */ diff --git a/include/env_internal.h b/include/env_internal.h index 6a69494646..fcb464263f 100644 --- a/include/env_internal.h +++ b/include/env_internal.h @@ -89,7 +89,7 @@ typedef struct environment_s { extern env_t embedded_environment; #endif /* ENV_IS_EMBEDDED */

-#ifdef DEFAULT_ENV_IS_RW +#ifdef CONFIG_DEFAULT_ENV_IS_RW

What is this change for?

extern char default_environment[]; #else extern const char default_environment[]; diff --git a/include/fdtdec.h b/include/fdtdec.h index aa61a0fca1..48937a7a46 100644 --- a/include/fdtdec.h +++ b/include/fdtdec.h @@ -657,6 +657,14 @@ int fdtdec_get_alias_seq(const void *blob, const char *base, int node, */ int fdtdec_get_alias_highest_id(const void *blob, const char *base);

Could you make this an ofnode_...() function instead? Then you can call ofnode_read_chosen_string() from your function.

We are trying to drop the fdtdec API.

+/**

• • Get baudrate from the dtb
• • @param blob Device tree blob (if NULL, then error is returned)
• • @return Baud rate value, or -ve error .

Return: Baud ...

(we changed to that syntax to work with Sphinx)

But this should become ofnode_read_baud(void)

Exported functions should be documented in the header file, not the C file

• */

+int fdtdec_get_baud_from_dtb(const void *blob);

/**

• Get a property from the /chosen node

diff --git a/include/serial.h b/include/serial.h index 42bdf3759c..48834b517c 100644 --- a/include/serial.h +++ b/include/serial.h @@ -337,6 +337,7 @@ int serial_setconfig(struct udevice *dev, uint config); */ int serial_getinfo(struct udevice *dev, struct serial_device_info *info);

+int serial_get_valid_baudrate(int baud);

check_valid_baudrate() would be better since it is checking the provided rate, not returning a valid rate (as I understand it).

This needs function docs

void atmel_serial_initialize(void); void mcf_serial_initialize(void); void mpc85xx_serial_initialize(void); diff --git a/lib/fdtdec.c b/lib/fdtdec.c index 0827e16859..2fcc12148e 100644 --- a/lib/fdtdec.c +++ b/lib/fdtdec.c @@ -570,6 +570,46 @@ int fdtdec_get_alias_highest_id(const void *blob, const char *base) return max; }

+#ifdef CONFIG_SERIAL_DT_BAUD +int fdtdec_get_baud_from_dtb(const void *blob) +{

•   const char *str, *p, *baud_start;
  

•   u32 baud;
  

•   if (!blob)
  

•           return -EFAULT;
  

•   str = fdtdec_get_chosen_prop(blob, "stdout-path");
  

•   if (!str)
  

•           return -EINVAL;
  

•   p = strchr(str, ':');
  

•   if (!p)
  

•           return -EINVAL;
  

•   baud = 0;
  

•   baud_start = p + 1;
  

It would help to have a comment about the format you are parsing, e.g. an example string.

I thought it was something like: "serial0:115200n8" in which case I think you could do:

p = strchr(str, ':') if (p) { uint baud = dectoul(p + 1, NULL);

...

}

•   while (*baud_start != '\0') {
  

•           /*
  

•            * Uart binding is <baud>{<parity>{<bits>{...}}}
  

•            * So the baudrate either is the whole string, or
  

•            * ends in the parity characters.
  

•            */
  

•           if (*baud_start == 'n' || *baud_start == 'o' ||
  

•               *baud_start == 'e')
  

•                   break;
  

•           baud = baud * 10 + (*baud_start - '0');
  

•           baud_start++;
  

•   }
  

•   if (serial_get_valid_baudrate(baud) == -EINVAL)
  

•           return -EINVAL;
  

ret = func ... if (ret) return ret

(i.e. don't change the error number, and catch all errors that it might return)

•   return baud;
  

+} +#endif

const char *fdtdec_get_chosen_prop(const void *blob, const char *name) { int chosen_node; -- 2.17.1

Regards, Simon