| Message ID | 20240127003607.501086-6-andre.draszik@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/5] clk: samsung: gs101: gpio_peric0_pclk needs to be kept on | expand |
On Mon, 2024-01-29 at 13:16 -0600, Sam Protsenko wrote: > That sounds reasonable. But I wonder if that bit (about making this > clock CLK_IS_CRITICAL to make earlycon functional) can be documented > somewhere. Perhaps in the serial driver (earlycon function), or > somewhere in device tree bindings? Because otherwise it might remain > an arcane knowledge and people won't be able to use earlycon later. > Anyways, for this patch: > > Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org> > > and if you think it makes sense to document the bit above, please do. Will do on top of https://lore.kernel.org/all/20240119104526.1221243-6-tudor.ambarus@linaro.org/ once that is in. Cheers, Andre'
On 1/30/24 09:31, André Draszik wrote: > On Mon, 2024-01-29 at 13:16 -0600, Sam Protsenko wrote: >> That sounds reasonable. But I wonder if that bit (about making this >> clock CLK_IS_CRITICAL to make earlycon functional) can be documented >> somewhere. Perhaps in the serial driver (earlycon function), or >> somewhere in device tree bindings? Because otherwise it might remain >> an arcane knowledge and people won't be able to use earlycon later. >> Anyways, for this patch: >> >> Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org> >> >> and if you think it makes sense to document the bit above, please do. > > Will do on top of > https://lore.kernel.org/all/20240119104526.1221243-6-tudor.ambarus@linaro.org/ > once that is in. > It was applied, it's in linux-next. I like the dt bindings idea, it's the first thing I check when dealing with new hardware. No idea though how to add comments just for a specific compatible. Shall be a description somewhere...
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,
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@linaro.org> --- drivers/clk/samsung/clk-gs101.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)