| Message ID | 20220930123239.15515-3-jim.shu@sifive.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Enhance maximum priority support of PLIC | expand |
Hi Jim, On Fri, Sep 30, 2022 at 2:32 PM Jim Shu <jim.shu@sifive.com> wrote: > > PLIC spec [1] requires interrupt source priority registers are WARL > field and the number of supported priority is power-of-2 to simplify SW > discovery. > > Existing QEMU RISC-V machine (e.g. shakti_c) don't strictly follow PLIC > spec, whose number of supported priority is not power-of-2. Just change > each bit of interrupt priority register to WARL field when the number of > supported priority is power-of-2. > > [1] https://github.com/riscv/riscv-plic-spec/blob/master/riscv-plic.adoc#interrupt-priorities > > Signed-off-by: Jim Shu <jim.shu@sifive.com> > --- > hw/intc/sifive_plic.c | 21 +++++++++++++++++++-- > 1 file changed, 19 insertions(+), 2 deletions(-) > > diff --git a/hw/intc/sifive_plic.c b/hw/intc/sifive_plic.c > index f864efa761..218ccff8bd 100644 > --- a/hw/intc/sifive_plic.c > +++ b/hw/intc/sifive_plic.c > @@ -180,7 +180,15 @@ static void sifive_plic_write(void *opaque, hwaddr addr, uint64_t value, > if (addr_between(addr, plic->priority_base, plic->num_sources << 2)) { > uint32_t irq = ((addr - plic->priority_base) >> 2) + 1; > > - if (value <= plic->num_priorities) { > + if ((plic->num_priorities + 1) & (plic->num_priorities)) { That's the opposite. If n is a power of 2, n & (n-1) == 0 (eg 8 & 7 == 0, 9 & 8 == 8). Note that n must be positive too. But I'm not sure it matters here. I'll let you decide. > + /* > + * if "num_priorities + 1" is power-of-2, make each register bit of > + * interrupt priority WARL (Write-Any-Read-Legal). Just filter > + * out the access to unsupported priority bits. > + */ > + plic->source_priority[irq] = value % (plic->num_priorities + 1); > + sifive_plic_update(plic); > + } else if (value <= plic->num_priorities) { > plic->source_priority[irq] = value; > sifive_plic_update(plic); > } > @@ -207,7 +215,16 @@ static void sifive_plic_write(void *opaque, hwaddr addr, uint64_t value, > uint32_t contextid = (addr & (plic->context_stride - 1)); > > if (contextid == 0) { > - if (value <= plic->num_priorities) { > + if ((plic->num_priorities + 1) & (plic->num_priorities)) { Same. > + /* > + * if "num_priorities + 1" is power-of-2, each register bit of > + * interrupt priority is WARL (Write-Any-Read-Legal). Just > + * filter out the access to unsupported priority bits. > + */ > + plic->target_priority[addrid] = value % > + (plic->num_priorities + 1); > + sifive_plic_update(plic); > + } else if (value <= plic->num_priorities) { > plic->target_priority[addrid] = value; > sifive_plic_update(plic); > } > -- > 2.17.1 Clément
hi Clément, Thank you very much. I'll fix it in the next version patch. Thanks, Jim Shu On Fri, Sep 30, 2022 at 8:58 PM Clément Chigot <chigot@adacore.com> wrote: > > Hi Jim, > > On Fri, Sep 30, 2022 at 2:32 PM Jim Shu <jim.shu@sifive.com> wrote: > > > > PLIC spec [1] requires interrupt source priority registers are WARL > > field and the number of supported priority is power-of-2 to simplify SW > > discovery. > > > > Existing QEMU RISC-V machine (e.g. shakti_c) don't strictly follow PLIC > > spec, whose number of supported priority is not power-of-2. Just change > > each bit of interrupt priority register to WARL field when the number of > > supported priority is power-of-2. > > > > [1] https://github.com/riscv/riscv-plic-spec/blob/master/riscv-plic.adoc#interrupt-priorities > > > > Signed-off-by: Jim Shu <jim.shu@sifive.com> > > --- > > hw/intc/sifive_plic.c | 21 +++++++++++++++++++-- > > 1 file changed, 19 insertions(+), 2 deletions(-) > > > > diff --git a/hw/intc/sifive_plic.c b/hw/intc/sifive_plic.c > > index f864efa761..218ccff8bd 100644 > > --- a/hw/intc/sifive_plic.c > > +++ b/hw/intc/sifive_plic.c > > @@ -180,7 +180,15 @@ static void sifive_plic_write(void *opaque, hwaddr addr, uint64_t value, > > if (addr_between(addr, plic->priority_base, plic->num_sources << 2)) { > > uint32_t irq = ((addr - plic->priority_base) >> 2) + 1; > > > > - if (value <= plic->num_priorities) { > > + if ((plic->num_priorities + 1) & (plic->num_priorities)) { > > That's the opposite. If n is a power of 2, n & (n-1) == 0 (eg 8 & 7 == > 0, 9 & 8 == 8). > Note that n must be positive too. But I'm not sure it matters here. > I'll let you decide. > > > + /* > > + * if "num_priorities + 1" is power-of-2, make each register bit of > > + * interrupt priority WARL (Write-Any-Read-Legal). Just filter > > + * out the access to unsupported priority bits. > > + */ > > + plic->source_priority[irq] = value % (plic->num_priorities + 1); > > + sifive_plic_update(plic); > > + } else if (value <= plic->num_priorities) { > > plic->source_priority[irq] = value; > > sifive_plic_update(plic); > > } > > @@ -207,7 +215,16 @@ static void sifive_plic_write(void *opaque, hwaddr addr, uint64_t value, > > uint32_t contextid = (addr & (plic->context_stride - 1)); > > > > if (contextid == 0) { > > - if (value <= plic->num_priorities) { > > + if ((plic->num_priorities + 1) & (plic->num_priorities)) { > > Same. > > > + /* > > + * if "num_priorities + 1" is power-of-2, each register bit of > > + * interrupt priority is WARL (Write-Any-Read-Legal). Just > > + * filter out the access to unsupported priority bits. > > + */ > > + plic->target_priority[addrid] = value % > > + (plic->num_priorities + 1); > > + sifive_plic_update(plic); > > + } else if (value <= plic->num_priorities) { > > plic->target_priority[addrid] = value; > > sifive_plic_update(plic); > > } > > -- > > 2.17.1 > > Clément
Hi Clément, > > > @@ -180,7 +180,15 @@ static void sifive_plic_write(void *opaque, hwaddr addr, uint64_t value, > > > if (addr_between(addr, plic->priority_base, plic->num_sources << 2)) { > > > uint32_t irq = ((addr - plic->priority_base) >> 2) + 1; > > > > > > - if (value <= plic->num_priorities) { > > > + if ((plic->num_priorities + 1) & (plic->num_priorities)) { > > > > That's the opposite. If n is a power of 2, n & (n-1) == 0 (eg 8 & 7 == > > 0, 9 & 8 == 8). > > Note that n must be positive too. But I'm not sure it matters here. > > I'll let you decide. > > num_priorities is a uint32_t variable so that n is always positive.
diff --git a/hw/intc/sifive_plic.c b/hw/intc/sifive_plic.c index f864efa761..218ccff8bd 100644 --- a/hw/intc/sifive_plic.c +++ b/hw/intc/sifive_plic.c @@ -180,7 +180,15 @@ static void sifive_plic_write(void *opaque, hwaddr addr, uint64_t value, if (addr_between(addr, plic->priority_base, plic->num_sources << 2)) { uint32_t irq = ((addr - plic->priority_base) >> 2) + 1; - if (value <= plic->num_priorities) { + if ((plic->num_priorities + 1) & (plic->num_priorities)) { + /* + * if "num_priorities + 1" is power-of-2, make each register bit of + * interrupt priority WARL (Write-Any-Read-Legal). Just filter + * out the access to unsupported priority bits. + */ + plic->source_priority[irq] = value % (plic->num_priorities + 1); + sifive_plic_update(plic); + } else if (value <= plic->num_priorities) { plic->source_priority[irq] = value; sifive_plic_update(plic); } @@ -207,7 +215,16 @@ static void sifive_plic_write(void *opaque, hwaddr addr, uint64_t value, uint32_t contextid = (addr & (plic->context_stride - 1)); if (contextid == 0) { - if (value <= plic->num_priorities) { + if ((plic->num_priorities + 1) & (plic->num_priorities)) { + /* + * if "num_priorities + 1" is power-of-2, each register bit of + * interrupt priority is WARL (Write-Any-Read-Legal). Just + * filter out the access to unsupported priority bits. + */ + plic->target_priority[addrid] = value % + (plic->num_priorities + 1); + sifive_plic_update(plic); + } else if (value <= plic->num_priorities) { plic->target_priority[addrid] = value; sifive_plic_update(plic); }
PLIC spec [1] requires interrupt source priority registers are WARL field and the number of supported priority is power-of-2 to simplify SW discovery. Existing QEMU RISC-V machine (e.g. shakti_c) don't strictly follow PLIC spec, whose number of supported priority is not power-of-2. Just change each bit of interrupt priority register to WARL field when the number of supported priority is power-of-2. [1] https://github.com/riscv/riscv-plic-spec/blob/master/riscv-plic.adoc#interrupt-priorities Signed-off-by: Jim Shu <jim.shu@sifive.com> --- hw/intc/sifive_plic.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)