Messages in this thread Patch in this message | | | From | Cristian Marussi <> | Subject | [RFC PATCH v2 8/8] firmware: arm_scmi: Make smc transport atomic | Date | Mon, 5 Jul 2021 18:10:22 +0100 |
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Substitute mutex usages with busy-waiting and declare smc transport as .atomic_capable.
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com> --- drivers/firmware/arm_scmi/smc.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-)
diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c index cab1d0d50d8e..e33985a02068 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 +15,7 @@ #include <linux/of.h> #include <linux/of_address.h> #include <linux/of_irq.h> +#include <linux/processor.h> #include <linux/slab.h> #include "common.h" @@ -23,14 +25,15 @@ * * @cinfo: SCMI channel info * @shmem: Transmit/Receive shared memory area - * @shmem_lock: Lock to protect access to Tx/Rx shared memory area + * @inflight: Atomic flag to protect access to Tx/Rx shared memory area * @func_id: smc/hvc call function id */ struct scmi_smc { struct scmi_chan_info *cinfo; struct scmi_shared_mem __iomem *shmem; - struct mutex shmem_lock; +#define INFLIGHT_NONE MSG_TOKEN_MAX + atomic_t inflight; u32 func_id; }; @@ -114,7 +117,7 @@ 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); + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); cinfo->transport_info = scmi_info; return 0; @@ -133,6 +136,15 @@ static int smc_chan_free(int id, void *p, void *data) return 0; } +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; +} + static int smc_send_message(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer) { @@ -140,16 +152,17 @@ 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); + spin_until_cond(smc_xfer_inflight(xfer, &scmi_info->inflight)); + shmem_tx_prepare(scmi_info->shmem, xfer); arm_smccc_1_1_invoke(scmi_info->func_id, 0, 0, 0, 0, 0, 0, 0, &res); /* Only SMCCC_RET_NOT_SUPPORTED is valid error code */ if (res.a0) { - mutex_unlock(&scmi_info->shmem_lock); + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); return -EOPNOTSUPP; } @@ -168,7 +181,7 @@ 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); + atomic_set(&scmi_info->inflight, INFLIGHT_NONE); } static bool @@ -194,4 +207,5 @@ const struct scmi_desc scmi_smc_desc = { .max_rx_timeout_ms = 30, .max_msg = 20, .max_msg_size = 128, + .atomic_capable = true, }; -- 2.17.1
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