On 1/27/24 00:35, André Draszik wrote:
> The peric0_top1_ipclk_0 and peric0_top1_pclk_0 are the clocks going to
> peric0/uart_usi, with pclk being the bus clock. Without pclk running,
> any bus access will hang.
> Unfortunately, in commit d97b6c902a40 ("arm64: dts: exynos: gs101:
> update USI UART to use peric0 clocks") the gs101 DT ended up specifying
> an incorrect pclkk in the respective node and instead the two clocks
> here were marked as critical.
>
> We have fixed the gs101 DT and can therefore drop this incorrect
> work-around here, the uart driver will claim these clocks as needed.
>
> Note that this commit has the side-effect of causing earlycon to stop
> to work sometime into the boot for two reasons:
> * peric0_top1_ipclk_0 requires its parent gout_cmu_peric0_ip to be
> running, but because earlycon doesn't deal with clocks that
> parent will be disabled when none of the other drivers that
> actually deal with clocks correctly require it to be running and
> the real serial driver (which does deal with clocks) hasn't taken
> over yet
> * hand-over between earlycon and serial driver appears to be
> fragile and clocks get enabled and disabled a few times, which
> also causes register access to hang while earlycon is still
> active
> Nonetheless we shouldn't keep these clocks running unconditionally just
> for earlycon. Clocks should be disabled where possible. If earlycon is
> required in the future, e.g. for debug, this commit can simply be
> reverted (locally!).
>
> Fixes: 893f133a040b ("clk: samsung: gs101: add support for cmu_peric0")
> Signed-off-by: André Draszik <andre.draszik@xxxxxxxxxx>
I find the logic fine:
Reviewed-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
> ---
> drivers/clk/samsung/clk-gs101.c | 6 ++----
> 1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/clk/samsung/clk-gs101.c b/drivers/clk/samsung/clk-gs101.c
> index 61bb0dcf84ee..5c338ac9231c 100644
> --- a/drivers/clk/samsung/clk-gs101.c
> +++ b/drivers/clk/samsung/clk-gs101.c
> @@ -2982,20 +2982,18 @@ static const struct samsung_gate_clock peric0_gate_clks[] __initconst = {
> "gout_peric0_peric0_top0_pclk_9", "mout_peric0_bus_user",
> CLK_CON_GAT_GOUT_BLK_PERIC0_UID_PERIC0_TOP0_IPCLKPORT_PCLK_9,
> 21, 0, 0),
> - /* Disabling this clock makes the system hang. Mark the clock as critical. */
> GATE(CLK_GOUT_PERIC0_PERIC0_TOP1_IPCLK_0,
> "gout_peric0_peric0_top1_ipclk_0", "dout_peric0_usi0_uart",
> CLK_CON_GAT_GOUT_BLK_PERIC0_UID_PERIC0_TOP1_IPCLKPORT_IPCLK_0,
> - 21, CLK_IS_CRITICAL, 0),
> + 21, 0, 0),
> GATE(CLK_GOUT_PERIC0_PERIC0_TOP1_IPCLK_2,
> "gout_peric0_peric0_top1_ipclk_2", "dout_peric0_usi14_usi",
> CLK_CON_GAT_GOUT_BLK_PERIC0_UID_PERIC0_TOP1_IPCLKPORT_IPCLK_2,
> 21, 0, 0),
> - /* Disabling this clock makes the system hang. Mark the clock as critical. */
> GATE(CLK_GOUT_PERIC0_PERIC0_TOP1_PCLK_0,
> "gout_peric0_peric0_top1_pclk_0", "mout_peric0_bus_user",
> CLK_CON_GAT_GOUT_BLK_PERIC0_UID_PERIC0_TOP1_IPCLKPORT_PCLK_0,
> - 21, CLK_IS_CRITICAL, 0),
> + 21, 0, 0),
> GATE(CLK_GOUT_PERIC0_PERIC0_TOP1_PCLK_2,
> "gout_peric0_peric0_top1_pclk_2", "mout_peric0_bus_user",
> CLK_CON_GAT_GOUT_BLK_PERIC0_UID_PERIC0_TOP1_IPCLKPORT_PCLK_2,
