On 2021/12/31 7:13, Martin Blumenstingl wrote:

[ EXTERNAL EMAIL ]

On Thu, Dec 30, 2021 at 11:21 AM Yu Tu [off-list ref] wrote:
[...]

quoted

@@ -270,14 +284,11 @@ static void meson_uart_reset(struct uart_port *port)
  static int meson_uart_startup(struct uart_port *port)
  {
         u32 val;
-       int ret = 0;
+       int ret;

-       val = readl(port->membase + AML_UART_CONTROL);
-       val |= AML_UART_CLEAR_ERR;
-       writel(val, port->membase + AML_UART_CONTROL);
-       val &= ~AML_UART_CLEAR_ERR;
-       writel(val, port->membase + AML_UART_CONTROL);
+       meson_uart_reset(port);

I suggest splitting this into a separate patch. In general I think
it's a good idea to re-use meson_uart_reset here if possible.
However, if during testing it turns out that this doesn't work then we
can revert this single patch which updates meson_uart_startup() only -
instead of reverting the whole transition to the common clock
framework.

I approve of your suggestion. I will make the next patch.

[...]

quoted

  static int meson_uart_request_port(struct uart_port *port)
  {
+       struct meson_uart_data *private_data = port->private_data;
+       int ret;
+
+       ret = clk_prepare_enable(private_data->pclk);
+       if (ret)
+               return ret;
+
+       ret = clk_prepare_enable(private_data->baud_clk);
+       if (ret) {
+               clk_disable_unprepare(private_data->pclk);
+               return ret;
+       }

This code is from my original suggestion - and I had a doubt there
which I forgot to add as a comment originally:
Can you confirm that accessing the UART controller registers works
even when "pclk" is turned off?
I am asking this because the common clock framework can access the
clocks at any time.
And I have seen SoCs which would hang when trying to access a module's
registers while the module's pclk is turned off.

On all meson platforms, the default pclk for all UART is turned on 
during the u-boot phase. When registering uart pclk in the kernel phase, 
the CLK_IGNORE_UNUSED flag is added. So the real shutdown is when the 
standby goes down, the parent clk shuts down.
.

[...]

quoted

         port->fifosize = 64;

commit 27d44e05d7b85d ("tty: serial: meson: retrieve port FIFO size
from DT") [0] from May 2021 has changed this line to:
   port->fifosize = fifosize;
So your patch currently does not apply to linux-next (or even Linus'
mainline tree).

So do I need to wait for [0] patch merged before I can continue to make 
changes ?
What can I do before?

[...]

quoted

  static const struct of_device_id meson_uart_dt_match[] = {
-       { .compatible = "amlogic,meson6-uart" },
-       { .compatible = "amlogic,meson8-uart" },
-       { .compatible = "amlogic,meson8b-uart" },
-       { .compatible = "amlogic,meson-gx-uart" },
+       {
+               .compatible = "amlogic,meson6-uart",
+               .data = (void *)false,
+       },
+       {
+               .compatible = "amlogic,meson8-uart",
+               .data = (void *)false,
+       },
+       {
+               .compatible = "amlogic,meson8b-uart",
+               .data = (void *)false,
+       },
+       {
+               .compatible = "amlogic,meson-gxbb-uart",
+               .data = (void *)false,
+       },
+       {
+               .compatible = "amlogic,meson-gxl-uart",
+               .data = (void *)true,
+       },
+       {
+               .compatible = "amlogic,meson-g12a-uart",
+               .data = (void *)true,
+       },
+       {
+               .compatible = "amlogic,meson-s4-uart",
+               .data = (void *)true,
+       },
+       /*
+        * deprecated, don't use anymore because it doesn't differentiate
+        * between GXBB and GXL which have different revisions of the UART IP.
+        */
+       {
+               .compatible = "amlogic,meson-gx-uart",
+               .data = (void *)false,
+       },

For this change I think it's also best to split it into separate
changes, similar to the dt-bindings:
1) deprecate and replace "amlogic,meson-gx-uart"
2) another one to add the S4 compatible string
3) and a third one with the big common clock framework change (adding
the .data attributes)

This is about the "Separate each logical change into a separate patch"
rule from the Linux kernel patch submission guide [1]
Also I hope that it will make it (at least a bit) easier for others to
also review this patch.

I quite agree with your suggestion. I'll do as you suggest.

Best regards,
Martin


[0] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/drivers/tty/serial/meson_uart.c?id=27d44e05d7b85d9d4cfe0a3c0663ea49752ece93
[1] https://www.kernel.org/doc/html/v4.17/process/submitting-patches.html#separate-your-changes

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