| Message ID | 20220519125706.593532-1-joel@jms.id.au (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | powerpc/microwatt: Add mmu bits to device tree | expand |
| Context | Check | Description |
|---|---|---|
| snowpatch_ozlabs/github-powerpc_clang | success | Successfully ran 7 jobs. |
| snowpatch_ozlabs/github-powerpc_selftests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_ppctests | success | Successfully ran 10 jobs. |
| snowpatch_ozlabs/github-powerpc_kernel_qemu | success | Successfully ran 24 jobs. |
| snowpatch_ozlabs/github-powerpc_sparse | success | Successfully ran 4 jobs. |
Excerpts from Joel Stanley's message of May 19, 2022 10:57 pm: > In commit 5402e239d09f ("powerpc/64s: Get LPID bit width from device > tree") the kernel tried to determine the pid and lpid bits from the > device tree. If they are not found, there is a fallback, but Microwatt > wasn't covered as has the unusual configuration of being both !HV and bare > metal. > > Set the values in the device tree to avoid having to add a special case. > The lpid value is the only one required, but add both for completeness. > > Fixes: 5402e239d09f ("powerpc/64s: Get LPID bit width from device tree") > Signed-off-by: Joel Stanley <joel@jms.id.au> LGTM... does Microwatt actually need 12 lpid bits, or does it just need the LPID 0 partition table entry? I wonder if you set it to 1. That's a minor nit though. Acked-by: Nicholas Piggin <npiggin@gmail.com> > --- > arch/powerpc/boot/dts/microwatt.dts | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/powerpc/boot/dts/microwatt.dts b/arch/powerpc/boot/dts/microwatt.dts > index 65b270a90f94..b69db1d275cd 100644 > --- a/arch/powerpc/boot/dts/microwatt.dts > +++ b/arch/powerpc/boot/dts/microwatt.dts > @@ -90,6 +90,8 @@ PowerPC,Microwatt@0 { > 64-bit; > d-cache-size = <0x1000>; > ibm,chip-id = <0>; > + ibm,mmu-lpid-bits = <12>; > + ibm,mmu-pid-bits = <20>; > }; > }; > > -- > 2.35.1 > >
On Fri, 2022-05-20 at 10:06 +1000, Nicholas Piggin wrote: > Excerpts from Joel Stanley's message of May 19, 2022 10:57 pm: > > In commit 5402e239d09f ("powerpc/64s: Get LPID bit width from device > > tree") the kernel tried to determine the pid and lpid bits from the > > device tree. If they are not found, there is a fallback, but Microwatt > > wasn't covered as has the unusual configuration of being both !HV and bare > > metal. > > > > Set the values in the device tree to avoid having to add a special case. > > The lpid value is the only one required, but add both for completeness. > > > > Fixes: 5402e239d09f ("powerpc/64s: Get LPID bit width from device tree") > > Signed-off-by: Joel Stanley <joel@jms.id.au> > > LGTM... does Microwatt actually need 12 lpid bits, or does it just need > the LPID 0 partition table entry? Microwatt just assumes LPID=0 as it doesn't actually have an LPID SPR. It just uses the first entry in the partition table. There are some details here: https://github.com/antonblanchard/microwatt/commit/18120f153d138f733fa7e8a89c3456bb93683f96 > I wonder if you set it to 1. That's a minor nit though. .. or even set it to 0. Mikey
On Fri, 20 May 2022 at 00:06, Nicholas Piggin <npiggin@gmail.com> wrote: > > Excerpts from Joel Stanley's message of May 19, 2022 10:57 pm: > > In commit 5402e239d09f ("powerpc/64s: Get LPID bit width from device > > tree") the kernel tried to determine the pid and lpid bits from the > > device tree. If they are not found, there is a fallback, but Microwatt > > wasn't covered as has the unusual configuration of being both !HV and bare > > metal. > > > > Set the values in the device tree to avoid having to add a special case. > > The lpid value is the only one required, but add both for completeness. > > > > Fixes: 5402e239d09f ("powerpc/64s: Get LPID bit width from device tree") > > Signed-off-by: Joel Stanley <joel@jms.id.au> > > LGTM... does Microwatt actually need 12 lpid bits, or does it just need > the LPID 0 partition table entry? I wonder if you set it to 1. That's > a minor nit though. 0, 1, 4, 5, 6, 7 fails. 8, 9, 10, 11, 12 work. I'll let someone else explain why that is! Oh, it's because we use it like this: arch/powerpc/include/asm/book3s/64/mmu.h:#define PATB_SIZE_SHIFT (mmu_lpid_bits + 4) and then arch/powerpc/mm/book3s64/radix_pgtable.c: set_ptcr_when_no_uv(__pa(partition_tb) | arch/powerpc/mm/book3s64/radix_pgtable.c: (PATB_SIZE_SHIFT - 12)); so anything less than 8 will result in a negative value there. The ISA says (from Figure 22 in 3.1, or 21 in 3.0B): Partition Table Size=2**(12+PATS), PATS<= 24. From this it's clear that 12 >= mmu_lpid_bits >= 24. (except there's only 4 bits for PATS in the ISA, so really the maximum is 16?) What's not clear to me is why we define PATB_SIZE_SHIFT as mmu_lpid_bits + 4. Cheers, Joel > > Acked-by: Nicholas Piggin <npiggin@gmail.com> > > > --- > > arch/powerpc/boot/dts/microwatt.dts | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/arch/powerpc/boot/dts/microwatt.dts b/arch/powerpc/boot/dts/microwatt.dts > > index 65b270a90f94..b69db1d275cd 100644 > > --- a/arch/powerpc/boot/dts/microwatt.dts > > +++ b/arch/powerpc/boot/dts/microwatt.dts > > @@ -90,6 +90,8 @@ PowerPC,Microwatt@0 { > > 64-bit; > > d-cache-size = <0x1000>; > > ibm,chip-id = <0>; > > + ibm,mmu-lpid-bits = <12>; > > + ibm,mmu-pid-bits = <20>; > > }; > > }; > > > > -- > > 2.35.1 > > > >
On Thu, 19 May 2022 22:27:06 +0930, Joel Stanley wrote: > In commit 5402e239d09f ("powerpc/64s: Get LPID bit width from device > tree") the kernel tried to determine the pid and lpid bits from the > device tree. If they are not found, there is a fallback, but Microwatt > wasn't covered as has the unusual configuration of being both !HV and bare > metal. > > Set the values in the device tree to avoid having to add a special case. > The lpid value is the only one required, but add both for completeness. > > [...] Applied to powerpc/next. [1/1] powerpc/microwatt: Add mmu bits to device tree https://git.kernel.org/powerpc/c/0ef1ffc7189521e293b4c5532659385dfddf8939 cheers
diff --git a/arch/powerpc/boot/dts/microwatt.dts b/arch/powerpc/boot/dts/microwatt.dts index 65b270a90f94..b69db1d275cd 100644 --- a/arch/powerpc/boot/dts/microwatt.dts +++ b/arch/powerpc/boot/dts/microwatt.dts @@ -90,6 +90,8 @@ PowerPC,Microwatt@0 { 64-bit; d-cache-size = <0x1000>; ibm,chip-id = <0>; + ibm,mmu-lpid-bits = <12>; + ibm,mmu-pid-bits = <20>; }; };
In commit 5402e239d09f ("powerpc/64s: Get LPID bit width from device tree") the kernel tried to determine the pid and lpid bits from the device tree. If they are not found, there is a fallback, but Microwatt wasn't covered as has the unusual configuration of being both !HV and bare metal. Set the values in the device tree to avoid having to add a special case. The lpid value is the only one required, but add both for completeness. Fixes: 5402e239d09f ("powerpc/64s: Get LPID bit width from device tree") Signed-off-by: Joel Stanley <joel@jms.id.au> --- arch/powerpc/boot/dts/microwatt.dts | 2 ++ 1 file changed, 2 insertions(+)