Messages in this thread |  | | Date | Wed, 9 Apr 2025 23:59:09 +0000 | | From | Yixun Lan <> | | Subject | Re: [PATCH v2 2/2] serial: 8250_of: add support for an optional bus clock |
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Hi Alex,
On 17:47 Wed 09 Apr , Alex Elder wrote: > On 4/9/25 4:43 PM, Yixun Lan wrote: > > Hi Alex, > > > > On 14:22 Wed 09 Apr , Alex Elder wrote: > >> The SpacemiT UART requires a bus clock to be enabled, in addition to > >> it's "normal" core clock. Look up the optional bus clock by name, > >> and if that's found, look up the core clock using the name "core". > >> > >> Supplying a bus clock is optional. If no bus clock is needed, the > >> the first/only clock is used for the core clock. > >> > >> Signed-off-by: Alex Elder <elder@riscstar.com> > >> --- > >> v2: Update logic to more check for the optional bus clock first > >> > >> drivers/tty/serial/8250/8250_of.c | 11 ++++++++++- > >> 1 file changed, 10 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c > >> index 11c860ea80f60..a90a5462aa72a 100644 > >> --- a/drivers/tty/serial/8250/8250_of.c > >> +++ b/drivers/tty/serial/8250/8250_of.c > >> @@ -123,7 +123,16 @@ static int of_platform_serial_setup(struct platform_device *ofdev, > >> > >> /* Get clk rate through clk driver if present */ > >> if (!port->uartclk) { > >> - info->clk = devm_clk_get_enabled(dev, NULL); > >> + struct clk *bus_clk; > > we also need to handle clk in suspend/resume procedure, so > > I think you need to put bus_clk inside struct of_serial_info.. > > OK, I didn't do anything for that in previous versions of the > series. > > I think that means we'd call clk_disable_unprepare() on > the bus clock after doing so for the function clock. And > clk_prepare_enable() on the bus clock before doing that for > the function clock in of_serial_resume(). That's easy. > right, pretty much similar to info->clk
> Is there anything further you think is required? There is > no clock rate associated with the bus clock that I know of, > so even if the function clock rate changes, the bus clock > can remain as-is. > no further info I know of, my best guess, the rate doesn't really matter, a wide clk range should just work fine.
> > > >> + > >> + bus_clk = devm_clk_get_optional_enabled(dev, "bus"); > > for the 'optional', we can interpret it's optional for other vendor > > UART, but a must required clk for SpacemiT's k1 UART controller > > > > would it better to guard this inside a compatible test or even introduce > > a flag in compatible data? > > I don't personally think so. We could, but the DT binding is going > out of its way to define when the bus clock is required. This is > simpler, and generic. > I would personally choose the way of introducing a flag of compatible data, but it's a lot change of the code (may not worth the effort)..
anyway, I'm fine with your current version, and yes, it's generic thanks for doing this..
-- Yixun Lan (dlan) Gentoo Linux Developer GPG Key ID AABEFD55
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