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mfd: macsmc: give atomic writes time for the SMC to answer #918

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Merged
RyanTheTide merged 1 commit into from
Nov 5, 2026
Merged

mfd: macsmc: give atomic writes time for the SMC to answer #918

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24 changes: 21 additions & 3 deletions drivers/mfd/macsmc.c
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/iopoll.h>
#include <linux/ktime.h>
#include <linux/math.h>
#include <linux/mfd/core.h>
#include <linux/mfd/macsmc.h>
Expand Down Expand Up @@ -46,6 +47,8 @@
#define SMC_RESULT SMC_MSG

#define SMC_TIMEOUT_MS 500
/* Restart and power-off go through atomic writes; give the SMC time. */
#define SMC_ATOMIC_TIMEOUT_MS 5000

static const struct mfd_cell apple_smc_devs[] = {
MFD_CELL_NAME("macsmc-input"),
Expand Down Expand Up @@ -283,6 +286,8 @@ int apple_smc_write_atomic(struct apple_smc *smc, smc_key key, const void *buf,
u8 result;
int ret, poll_ret;
u64 msg;
ktime_t t0;
s64 us;

if (size > SMC_MAX_SIZE || size == 0)
return -EINVAL;
Expand All @@ -296,9 +301,17 @@ int apple_smc_write_atomic(struct apple_smc *smc, smc_key key, const void *buf,
* release its SRAM. Its late reply does: take it if it has arrived.
*/
if (smc->atomic_pending) {
ret = apple_rtkit_poll(smc->rtk);
if (ret < 0 || smc->atomic_pending)
/* Wait for the earlier command's late reply instead of giving up. */
ret = read_poll_timeout_atomic(apple_rtkit_poll, poll_ret,
poll_ret < 0 || !smc->atomic_pending,
100, SMC_ATOMIC_TIMEOUT_MS * USEC_PER_MSEC,
false, smc->rtk);
if (poll_ret < 0 || smc->atomic_pending) {
dev_err(smc->dev, "atomic: earlier command still pending (%d/%d)\n",
ret, poll_ret);
return -EBUSY;
}
dev_warn(smc->dev, "atomic: earlier command's reply arrived late\n");
}

memcpy_toio(smc->shmem.iomem, buf, size);
Expand All @@ -317,10 +330,15 @@ int apple_smc_write_atomic(struct apple_smc *smc, smc_key key, const void *buf,
return ret;
}

t0 = ktime_get();
ret = read_poll_timeout_atomic(apple_rtkit_poll, poll_ret,
poll_ret < 0 || !smc->atomic_pending,
100, SMC_TIMEOUT_MS * USEC_PER_MSEC,
100, SMC_ATOMIC_TIMEOUT_MS * USEC_PER_MSEC,
false, smc->rtk);
us = ktime_us_delta(ktime_get(), t0);
if (us > 100 * USEC_PER_MSEC || ret < 0 || smc->atomic_pending)
dev_warn(smc->dev, "atomic: key %p4ch reply after %lld us (ret %d)\n",
&key, us, ret);
if (poll_ret < 0) {
dev_err(smc->dev, "RTKit poll failed (%llx)", msg);
return poll_ret;
Expand Down