| Message ID | 20230209232302.25658-1-palmer@rivosinc.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | clocksource/drivers/riscv: Refuse to probe on T-Head | expand |
| Context | Check | Description |
|---|---|---|
| conchuod/cover_letter | success | Single patches do not need cover letters |
| conchuod/tree_selection | success | Guessed tree name to be for-next |
| conchuod/fixes_present | success | Fixes tag not required for -next series |
| conchuod/maintainers_pattern | success | MAINTAINERS pattern errors before the patch: 13 and now 13 |
| conchuod/verify_signedoff | success | Signed-off-by tag matches author and committer |
| conchuod/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| conchuod/build_rv64_clang_allmodconfig | success | Errors and warnings before: 0 this patch: 0 |
| conchuod/module_param | success | Was 0 now: 0 |
| conchuod/build_rv64_gcc_allmodconfig | success | Errors and warnings before: 0 this patch: 0 |
| conchuod/alphanumeric_selects | success | Out of order selects before the patch: 59 and now 59 |
| conchuod/build_rv32_defconfig | success | Build OK |
| conchuod/dtb_warn_rv64 | success | Errors and warnings before: 2 this patch: 2 |
| conchuod/header_inline | success | No static functions without inline keyword in header files |
| conchuod/checkpatch | warning | WARNING: 'interrups' may be misspelled - perhaps 'interrupts'? |
| conchuod/source_inline | success | Was 0 now: 0 |
| conchuod/build_rv64_nommu_k210_defconfig | success | Build OK |
| conchuod/verify_fixes | success | No Fixes tag |
| conchuod/build_rv64_nommu_virt_defconfig | success | Build OK |
Hi Palmer, On 2/9/23 17:23, Palmer Dabbelt wrote: > From: Palmer Dabbelt <palmer@rivosinc.com> > > As of d9f15a9de44a ("Revert "clocksource/drivers/riscv: Events are > stopped during CPU suspend"") this driver no longer functions correctly > for the T-Head firmware. That shouldn't impact any users, as we've got The current situation is that the C9xx CLINT binding was just accepted, so the CLINT is not yet described in any devicetree. So at least with upstream OpenSBI, which needs the CLINT DT node, the SBI timer extension never worked at all. > a functioning driver that's higher priority, but let's just be safe and > ban it from probing at all. > > Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> > --- > This feel super ugly to me, but I'm not sure how to do this more > cleanly. I'm not even sure if it's necessary, but I just ran back into > the driver reviewing some other patches so I figured I'd say something. This is not necessary as long as we add the riscv,timer node with the riscv,timer-cannot-wake-cpu property before we add the CLINT node. So it should not be a problem for any C9xx platform going forward. Regards, Samuel > --- > drivers/clocksource/timer-riscv.c | 16 ++++++++++++++++ > 1 file changed, 16 insertions(+) > > diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c > index a0d66fabf073..d2d0236d1ae6 100644 > --- a/drivers/clocksource/timer-riscv.c > +++ b/drivers/clocksource/timer-riscv.c > @@ -139,6 +139,22 @@ static int __init riscv_timer_init_dt(struct device_node *n) > if (cpuid != smp_processor_id()) > return 0; > > + /* > + * The T-Head firmware does not route timer interrups to the core > + * during non-retentive suspend. This is allowed by the specifications > + * (no interrupts are required to wake up the core during non-retentive > + * suspend), but most systems don't behave that way and Linux just > + * assumes that interrupts work. > + * > + * There's another timer for the T-Head sytems that behave this way > + * that is already probed by default, but just to be sure skip > + * initializing the SBI driver as it'll just break things later. > + */ > + if (sbi_get_mvendorid() == THEAD_VENDOR_ID) { > + pr_debug_once("Skipping SBI timer on T-Head due to missed wakeups"); > + return 0; > + } > + > domain = NULL; > child = of_get_compatible_child(n, "riscv,cpu-intc"); > if (!child) {
On Thu, 09 Feb 2023 15:35:53 PST (-0800), samuel@sholland.org wrote: > Hi Palmer, > > On 2/9/23 17:23, Palmer Dabbelt wrote: >> From: Palmer Dabbelt <palmer@rivosinc.com> >> >> As of d9f15a9de44a ("Revert "clocksource/drivers/riscv: Events are >> stopped during CPU suspend"") this driver no longer functions correctly >> for the T-Head firmware. That shouldn't impact any users, as we've got > > The current situation is that the C9xx CLINT binding was just accepted, > so the CLINT is not yet described in any devicetree. So at least with > upstream OpenSBI, which needs the CLINT DT node, the SBI timer extension > never worked at all. > >> a functioning driver that's higher priority, but let's just be safe and >> ban it from probing at all. >> >> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> >> --- >> This feel super ugly to me, but I'm not sure how to do this more >> cleanly. I'm not even sure if it's necessary, but I just ran back into >> the driver reviewing some other patches so I figured I'd say something. > > This is not necessary as long as we add the riscv,timer node with the > riscv,timer-cannot-wake-cpu property before we add the CLINT node. So it > should not be a problem for any C9xx platform going forward. Awesome, that sounds way better. > > Regards, > Samuel > >> --- >> drivers/clocksource/timer-riscv.c | 16 ++++++++++++++++ >> 1 file changed, 16 insertions(+) >> >> diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c >> index a0d66fabf073..d2d0236d1ae6 100644 >> --- a/drivers/clocksource/timer-riscv.c >> +++ b/drivers/clocksource/timer-riscv.c >> @@ -139,6 +139,22 @@ static int __init riscv_timer_init_dt(struct device_node *n) >> if (cpuid != smp_processor_id()) >> return 0; >> >> + /* >> + * The T-Head firmware does not route timer interrups to the core >> + * during non-retentive suspend. This is allowed by the specifications >> + * (no interrupts are required to wake up the core during non-retentive >> + * suspend), but most systems don't behave that way and Linux just >> + * assumes that interrupts work. >> + * >> + * There's another timer for the T-Head sytems that behave this way >> + * that is already probed by default, but just to be sure skip >> + * initializing the SBI driver as it'll just break things later. >> + */ >> + if (sbi_get_mvendorid() == THEAD_VENDOR_ID) { >> + pr_debug_once("Skipping SBI timer on T-Head due to missed wakeups"); >> + return 0; >> + } >> + >> domain = NULL; >> child = of_get_compatible_child(n, "riscv,cpu-intc"); >> if (!child) {
Hey Palmer, On Thu, Feb 09, 2023 at 03:23:02PM -0800, Palmer Dabbelt wrote: > From: Palmer Dabbelt <palmer@rivosinc.com> > > As of d9f15a9de44a ("Revert "clocksource/drivers/riscv: Events are > stopped during CPU suspend"") this driver no longer functions correctly > for the T-Head firmware. That shouldn't impact any users, as we've got > a functioning driver that's higher priority, but let's just be safe and > ban it from probing at all. > > Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> > --- > This feel super ugly to me, but I'm not sure how to do this more > cleanly. I'm not even sure if it's necessary, but I just ran back into > the driver reviewing some other patches so I figured I'd say something. I'm not super sure what you're trying to fix here. That revert went through to restore behaviour for the SiFive stuff that do deliver events in suspend. Subsequently, we added a DT property (probably the wrong one tbh, but that's all said and done now) that communicates that a timer is incapable of waking the cpus. See commit 98ce3981716c ("dt-bindings: timer: Add bindings for the RISC-V timer device") & the full patchset is at: https://lore.kernel.org/linux-riscv/20230103141102.772228-1-apatel@ventanamicro.com/ AFAIU, the binding for the T-HEAD clint was only accepted in the last week & there's nothing actually using this timer. IIRC, when I wanted to test the timer, Samuel cooked me up a WIP openSBI etc to enable it. So ye, I don't think this is needed fortunately! Cheers, Conor.
On Thu, 09 Feb 2023 15:40:45 PST (-0800), Conor Dooley wrote: > Hey Palmer, > > On Thu, Feb 09, 2023 at 03:23:02PM -0800, Palmer Dabbelt wrote: >> From: Palmer Dabbelt <palmer@rivosinc.com> >> >> As of d9f15a9de44a ("Revert "clocksource/drivers/riscv: Events are >> stopped during CPU suspend"") this driver no longer functions correctly >> for the T-Head firmware. That shouldn't impact any users, as we've got >> a functioning driver that's higher priority, but let's just be safe and >> ban it from probing at all. >> >> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> >> --- >> This feel super ugly to me, but I'm not sure how to do this more >> cleanly. I'm not even sure if it's necessary, but I just ran back into >> the driver reviewing some other patches so I figured I'd say something. > > I'm not super sure what you're trying to fix here. That revert went > through to restore behaviour for the SiFive stuff that do deliver events > in suspend. My worry was that we'd end up probing the SBI driver on T-Head systems, where it doesn't work (as the combination of SBI timer and SBI suspend depends on unspecified behavior). So we'd be better off just failing early and obviously in the case, rather than letting users think they could get away with only the SBI drivers. > Subsequently, we added a DT property (probably the wrong one tbh, but > that's all said and done now) that communicates that a timer is > incapable of waking the cpus. See commit 98ce3981716c ("dt-bindings: > timer: Add bindings for the RISC-V timer device") & the full patchset is > at: > https://lore.kernel.org/linux-riscv/20230103141102.772228-1-apatel@ventanamicro.com/ > > AFAIU, the binding for the T-HEAD clint was only accepted in the last > week & there's nothing actually using this timer. IIRC, when I wanted to > test the timer, Samuel cooked me up a WIP openSBI etc to enable it. That makes sense. I'd assumed these DTs just had the SBI timer in there (as a bunch of other stuff requires it), but from Samuel's reply it sounds like I was just wrong here. I guess we're sort of in a grey area for DTs that aren't in the kernel source tree, but this code is ugly enough I'm OK just ignoring those. > So ye, I don't think this is needed fortunately! Ya, I think so too. > > Cheers, > Conor.
diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c index a0d66fabf073..d2d0236d1ae6 100644 --- a/drivers/clocksource/timer-riscv.c +++ b/drivers/clocksource/timer-riscv.c @@ -139,6 +139,22 @@ static int __init riscv_timer_init_dt(struct device_node *n) if (cpuid != smp_processor_id()) return 0; + /* + * The T-Head firmware does not route timer interrups to the core + * during non-retentive suspend. This is allowed by the specifications + * (no interrupts are required to wake up the core during non-retentive + * suspend), but most systems don't behave that way and Linux just + * assumes that interrupts work. + * + * There's another timer for the T-Head sytems that behave this way + * that is already probed by default, but just to be sure skip + * initializing the SBI driver as it'll just break things later. + */ + if (sbi_get_mvendorid() == THEAD_VENDOR_ID) { + pr_debug_once("Skipping SBI timer on T-Head due to missed wakeups"); + return 0; + } + domain = NULL; child = of_get_compatible_child(n, "riscv,cpu-intc"); if (!child) {