| Message ID | 20211129191156.29322-13-cristian.marussi@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Introduce atomic support for SCMI transports | expand |
On Mon, Nov 29, 2021 at 07:11:52PM +0000, Cristian Marussi wrote: > Add a Kernel configuration option to enable SCMI SMC transport atomic > mode operation for selected SCMI transactions and leave it as default > disabled. > > Substitute mutex usages with busy-waiting and declare smc transport as > .atomic_enabled if such Kernel configuration option is enabled. > > Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> > --- > v5 --> v6 > - remove usage of atomic_capable > - removed needless union > - reviewed Kconfig help > v4 --> v5 > - removed RFC tag > - add CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE option > - add .atomic_enable support > - make atomic_capable dependent on > CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > - make also usage of mutexes vs busy-waiting dependent on > CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > --- > drivers/firmware/arm_scmi/Kconfig | 14 +++++++ > drivers/firmware/arm_scmi/smc.c | 66 ++++++++++++++++++++++++++++--- > 2 files changed, 74 insertions(+), 6 deletions(-) > > diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig > index 638ecec89ff1..d429326433d1 100644 > --- a/drivers/firmware/arm_scmi/Kconfig > +++ b/drivers/firmware/arm_scmi/Kconfig > @@ -78,6 +78,20 @@ config ARM_SCMI_TRANSPORT_SMC > If you want the ARM SCMI PROTOCOL stack to include support for a > transport based on SMC, answer Y. > > +config ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > + bool "Enable atomic mode support for SCMI SMC transport" > + depends on ARM_SCMI_TRANSPORT_SMC > + help > + Enable support of atomic operation for SCMI SMC based transport. > + > + If you want the SCMI SMC based transport to operate in atomic > + mode, avoiding any kind of sleeping behaviour for selected > + transactions on the TX path, answer Y. > + Enabling atomic mode operations allows any SCMI driver using this > + transport to optionally ask for atomic SCMI transactions and operate > + in atomic context too, at the price of using a number of busy-waiting > + primitives all over instead. If unsure say N. > + > config ARM_SCMI_TRANSPORT_VIRTIO > bool "SCMI transport based on VirtIO" > depends on VIRTIO=y || VIRTIO=ARM_SCMI_PROTOCOL > diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c > index b2f31d3feb10..0fc49cb49185 100644 > --- a/drivers/firmware/arm_scmi/smc.c > +++ b/drivers/firmware/arm_scmi/smc.c > @@ -7,6 +7,7 @@ > */ > > #include <linux/arm-smccc.h> > +#include <linux/atomic.h> > #include <linux/device.h> > #include <linux/err.h> > #include <linux/interrupt.h> > @@ -14,6 +15,9 @@ > #include <linux/of.h> > #include <linux/of_address.h> > #include <linux/of_irq.h> > +#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > +#include <linux/processor.h> > +#endif > #include <linux/slab.h> > > #include "common.h" > @@ -23,14 +27,23 @@ > * > * @cinfo: SCMI channel info > * @shmem: Transmit/Receive shared memory area > - * @shmem_lock: Lock to protect access to Tx/Rx shared memory area > + * @shmem_lock: Lock to protect access to Tx/Rx shared memory area. > + * Used when NOT operating in atomic mode. > + * @inflight: Atomic flag to protect access to Tx/Rx shared memory area. > + * Used when operating in atomic mode. > * @func_id: smc/hvc call function id > */ > > struct scmi_smc { > struct scmi_chan_info *cinfo; > struct scmi_shared_mem __iomem *shmem; > +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > + /* Protect access to shmem area */ > struct mutex shmem_lock; Ditto here, do we really need to do this saving ? I would wait until someone really complains about space. It unnecessarily makes it hard to read. > +#else > +#define INFLIGHT_NONE MSG_TOKEN_MAX > + atomic_t inflight; > +#endif > u32 func_id; > }; > > @@ -54,6 +67,46 @@ static bool smc_chan_available(struct device *dev, int idx) > return true; > } > > +static inline void smc_channel_lock_init(struct scmi_smc *scmi_info) > +{ > +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > + mutex_init(&scmi_info->shmem_lock); > +#else > + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); You can do both if you remove conditional definition of struct. > +#endif > +} > + > +#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > +static bool smc_xfer_inflight(struct scmi_xfer *xfer, atomic_t *inflight) > +{ > + int ret; > + > + ret = atomic_cmpxchg(inflight, INFLIGHT_NONE, xfer->hdr.seq); > + > + return ret == INFLIGHT_NONE; > +} > +#endif > + > +static inline void > +smc_channel_lock_acquire(struct scmi_smc *scmi_info, > + struct scmi_xfer *xfer __maybe_unused) > +{ > +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE If possible make it based some local variable or you can always do if (IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE))
On Mon, Dec 13, 2021 at 11:42:33AM +0000, Sudeep Holla wrote: > On Mon, Nov 29, 2021 at 07:11:52PM +0000, Cristian Marussi wrote: > > Add a Kernel configuration option to enable SCMI SMC transport atomic > > mode operation for selected SCMI transactions and leave it as default > > disabled. > > > > Substitute mutex usages with busy-waiting and declare smc transport as > > .atomic_enabled if such Kernel configuration option is enabled. > > > > Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> > > --- > > v5 --> v6 > > - remove usage of atomic_capable > > - removed needless union > > - reviewed Kconfig help > > v4 --> v5 > > - removed RFC tag > > - add CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE option > > - add .atomic_enable support > > - make atomic_capable dependent on > > CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > > - make also usage of mutexes vs busy-waiting dependent on > > CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > > --- > > drivers/firmware/arm_scmi/Kconfig | 14 +++++++ > > drivers/firmware/arm_scmi/smc.c | 66 ++++++++++++++++++++++++++++--- > > 2 files changed, 74 insertions(+), 6 deletions(-) > > > > diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig > > index 638ecec89ff1..d429326433d1 100644 > > --- a/drivers/firmware/arm_scmi/Kconfig > > +++ b/drivers/firmware/arm_scmi/Kconfig > > @@ -78,6 +78,20 @@ config ARM_SCMI_TRANSPORT_SMC > > If you want the ARM SCMI PROTOCOL stack to include support for a > > transport based on SMC, answer Y. > > > > +config ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > > + bool "Enable atomic mode support for SCMI SMC transport" > > + depends on ARM_SCMI_TRANSPORT_SMC > > + help > > + Enable support of atomic operation for SCMI SMC based transport. > > + > > + If you want the SCMI SMC based transport to operate in atomic > > + mode, avoiding any kind of sleeping behaviour for selected > > + transactions on the TX path, answer Y. > > + Enabling atomic mode operations allows any SCMI driver using this > > + transport to optionally ask for atomic SCMI transactions and operate > > + in atomic context too, at the price of using a number of busy-waiting > > + primitives all over instead. If unsure say N. > > + > > config ARM_SCMI_TRANSPORT_VIRTIO > > bool "SCMI transport based on VirtIO" > > depends on VIRTIO=y || VIRTIO=ARM_SCMI_PROTOCOL > > diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c > > index b2f31d3feb10..0fc49cb49185 100644 > > --- a/drivers/firmware/arm_scmi/smc.c > > +++ b/drivers/firmware/arm_scmi/smc.c > > @@ -7,6 +7,7 @@ > > */ > > > > #include <linux/arm-smccc.h> > > +#include <linux/atomic.h> > > #include <linux/device.h> > > #include <linux/err.h> > > #include <linux/interrupt.h> > > @@ -14,6 +15,9 @@ > > #include <linux/of.h> > > #include <linux/of_address.h> > > #include <linux/of_irq.h> > > +#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > > +#include <linux/processor.h> > > +#endif > > #include <linux/slab.h> > > > > #include "common.h" > > @@ -23,14 +27,23 @@ > > * > > * @cinfo: SCMI channel info > > * @shmem: Transmit/Receive shared memory area > > - * @shmem_lock: Lock to protect access to Tx/Rx shared memory area > > + * @shmem_lock: Lock to protect access to Tx/Rx shared memory area. > > + * Used when NOT operating in atomic mode. > > + * @inflight: Atomic flag to protect access to Tx/Rx shared memory area. > > + * Used when operating in atomic mode. > > * @func_id: smc/hvc call function id > > */ > > > > struct scmi_smc { > > struct scmi_chan_info *cinfo; > > struct scmi_shared_mem __iomem *shmem; > > +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > > + /* Protect access to shmem area */ > > struct mutex shmem_lock; > > Ditto here, do we really need to do this saving ? I would wait until someone > really complains about space. It unnecessarily makes it hard to read. > Yes, indeed I can remove ifdeffery and go with runtime checks. I'll do. > > +#else > > +#define INFLIGHT_NONE MSG_TOKEN_MAX > > + atomic_t inflight; > > +#endif > > u32 func_id; > > }; > > > > @@ -54,6 +67,46 @@ static bool smc_chan_available(struct device *dev, int idx) > > return true; > > } > > > > +static inline void smc_channel_lock_init(struct scmi_smc *scmi_info) > > +{ > > +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > > + mutex_init(&scmi_info->shmem_lock); > > +#else > > + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); > > You can do both if you remove conditional definition of struct. > Yes. > > +#endif > > +} > > + > > +#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > > +static bool smc_xfer_inflight(struct scmi_xfer *xfer, atomic_t *inflight) > > +{ > > + int ret; > > + > > + ret = atomic_cmpxchg(inflight, INFLIGHT_NONE, xfer->hdr.seq); > > + > > + return ret == INFLIGHT_NONE; > > +} > > +#endif > > + > > +static inline void > > +smc_channel_lock_acquire(struct scmi_smc *scmi_info, > > + struct scmi_xfer *xfer __maybe_unused) > > +{ > > +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE > > If possible make it based some local variable or you can always do > > if (IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE)) > I'll do. Thanks, Cristian
diff --git a/drivers/firmware/arm_scmi/Kconfig b/drivers/firmware/arm_scmi/Kconfig index 638ecec89ff1..d429326433d1 100644 --- a/drivers/firmware/arm_scmi/Kconfig +++ b/drivers/firmware/arm_scmi/Kconfig @@ -78,6 +78,20 @@ config ARM_SCMI_TRANSPORT_SMC If you want the ARM SCMI PROTOCOL stack to include support for a transport based on SMC, answer Y. +config ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + bool "Enable atomic mode support for SCMI SMC transport" + depends on ARM_SCMI_TRANSPORT_SMC + help + Enable support of atomic operation for SCMI SMC based transport. + + If you want the SCMI SMC based transport to operate in atomic + mode, avoiding any kind of sleeping behaviour for selected + transactions on the TX path, answer Y. + Enabling atomic mode operations allows any SCMI driver using this + transport to optionally ask for atomic SCMI transactions and operate + in atomic context too, at the price of using a number of busy-waiting + primitives all over instead. If unsure say N. + config ARM_SCMI_TRANSPORT_VIRTIO bool "SCMI transport based on VirtIO" depends on VIRTIO=y || VIRTIO=ARM_SCMI_PROTOCOL diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c index b2f31d3feb10..0fc49cb49185 100644 --- a/drivers/firmware/arm_scmi/smc.c +++ b/drivers/firmware/arm_scmi/smc.c @@ -7,6 +7,7 @@ */ #include <linux/arm-smccc.h> +#include <linux/atomic.h> #include <linux/device.h> #include <linux/err.h> #include <linux/interrupt.h> @@ -14,6 +15,9 @@ #include <linux/of.h> #include <linux/of_address.h> #include <linux/of_irq.h> +#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE +#include <linux/processor.h> +#endif #include <linux/slab.h> #include "common.h" @@ -23,14 +27,23 @@ * * @cinfo: SCMI channel info * @shmem: Transmit/Receive shared memory area - * @shmem_lock: Lock to protect access to Tx/Rx shared memory area + * @shmem_lock: Lock to protect access to Tx/Rx shared memory area. + * Used when NOT operating in atomic mode. + * @inflight: Atomic flag to protect access to Tx/Rx shared memory area. + * Used when operating in atomic mode. * @func_id: smc/hvc call function id */ struct scmi_smc { struct scmi_chan_info *cinfo; struct scmi_shared_mem __iomem *shmem; +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + /* Protect access to shmem area */ struct mutex shmem_lock; +#else +#define INFLIGHT_NONE MSG_TOKEN_MAX + atomic_t inflight; +#endif u32 func_id; }; @@ -54,6 +67,46 @@ static bool smc_chan_available(struct device *dev, int idx) return true; } +static inline void smc_channel_lock_init(struct scmi_smc *scmi_info) +{ +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + mutex_init(&scmi_info->shmem_lock); +#else + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); +#endif +} + +#ifdef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE +static bool smc_xfer_inflight(struct scmi_xfer *xfer, atomic_t *inflight) +{ + int ret; + + ret = atomic_cmpxchg(inflight, INFLIGHT_NONE, xfer->hdr.seq); + + return ret == INFLIGHT_NONE; +} +#endif + +static inline void +smc_channel_lock_acquire(struct scmi_smc *scmi_info, + struct scmi_xfer *xfer __maybe_unused) +{ +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + mutex_lock(&scmi_info->shmem_lock); +#else + spin_until_cond(smc_xfer_inflight(xfer, &scmi_info->inflight)); +#endif +} + +static inline void smc_channel_lock_release(struct scmi_smc *scmi_info) +{ +#ifndef CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE + mutex_unlock(&scmi_info->shmem_lock); +#else + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); +#endif +} + static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev, bool tx) { @@ -114,7 +167,7 @@ static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev, scmi_info->func_id = func_id; scmi_info->cinfo = cinfo; - mutex_init(&scmi_info->shmem_lock); + smc_channel_lock_init(scmi_info); cinfo->transport_info = scmi_info; return 0; @@ -140,10 +193,10 @@ static int smc_send_message(struct scmi_chan_info *cinfo, struct arm_smccc_res res; /* - * Channel lock will be released only once response has been + * Channel will be released only once response has been * surely fully retrieved, so after .mark_txdone() */ - mutex_lock(&scmi_info->shmem_lock); + smc_channel_lock_acquire(scmi_info, xfer); shmem_tx_prepare(scmi_info->shmem, xfer); @@ -151,7 +204,7 @@ static int smc_send_message(struct scmi_chan_info *cinfo, /* Only SMCCC_RET_NOT_SUPPORTED is valid error code */ if (res.a0) { - mutex_unlock(&scmi_info->shmem_lock); + smc_channel_lock_release(scmi_info); return -EOPNOTSUPP; } @@ -170,7 +223,7 @@ static void smc_mark_txdone(struct scmi_chan_info *cinfo, int ret) { struct scmi_smc *scmi_info = cinfo->transport_info; - mutex_unlock(&scmi_info->shmem_lock); + smc_channel_lock_release(scmi_info); } static const struct scmi_transport_ops scmi_smc_ops = { @@ -196,4 +249,5 @@ const struct scmi_desc scmi_smc_desc = { * from the shared memory area. */ .sync_cmds_atomic_replies = true, + .atomic_enabled = IS_ENABLED(CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE), };
Add a Kernel configuration option to enable SCMI SMC transport atomic mode operation for selected SCMI transactions and leave it as default disabled. Substitute mutex usages with busy-waiting and declare smc transport as .atomic_enabled if such Kernel configuration option is enabled. Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> --- v5 --> v6 - remove usage of atomic_capable - removed needless union - reviewed Kconfig help v4 --> v5 - removed RFC tag - add CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE option - add .atomic_enable support - make atomic_capable dependent on CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE - make also usage of mutexes vs busy-waiting dependent on CONFIG_ARM_SCMI_TRANSPORT_SMC_ATOMIC_ENABLE --- drivers/firmware/arm_scmi/Kconfig | 14 +++++++ drivers/firmware/arm_scmi/smc.c | 66 ++++++++++++++++++++++++++++--- 2 files changed, 74 insertions(+), 6 deletions(-)