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Fri, 12 Jun 2026 15:33:54 -0400 (EDT) Date: Fri, 12 Jun 2026 21:33:53 +0200 From: Janne Grunau To: Sasha Finkelstein Cc: Sven Peter , Neal Gompa , Sebastian Reichel , asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] power: supply: macsmc: Support macOS 27 SMC firmware Message-ID: <20260612193353.GA7993@robin.jannau.net> References: <20260612-gate-power-v2-1-de76cb9bb7ef@chaosmail.tech> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260612-gate-power-v2-1-de76cb9bb7ef@chaosmail.tech> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260612_123359_836337_A2C9D56A X-CRM114-Status: GOOD ( 28.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Jun 12, 2026 at 08:36:03PM +0200, Sasha Finkelstein wrote: > The SMC firmware included in macOS 27 changed the size of BCF0 key from > 4 to 1 bytes. This key is used for indicating that battery state is > critically low. > > Reviewed-by: Sven Peter > Signed-off-by: Sasha Finkelstein I think Fixes: 0ebf821cf6c7 ("power: supply: Add macsmc-power driver for Apple Silicon") and "Cc: stable" could be justified. Timing is a little unfortunate with v7.1 expected on sunday. > --- > Changes in v2: > - Addressing review feedback > - Link to v1: https://patch.msgid.link/20260611-gate-power-v1-1-8a62721086c7@chaosmail.tech > --- > drivers/power/supply/macsmc-power.c | 35 ++++++++++++++++++++++++++++++++--- > 1 file changed, 32 insertions(+), 3 deletions(-) > > diff --git a/drivers/power/supply/macsmc-power.c b/drivers/power/supply/macsmc-power.c > index 33ca07460f3a..747315e372bc 100644 > --- a/drivers/power/supply/macsmc-power.c > +++ b/drivers/power/supply/macsmc-power.c > @@ -86,6 +86,7 @@ struct macsmc_power { > bool has_ch0i; /* Force discharge (Older firmware) */ > bool has_ch0c; /* Inhibit charge (Older firmware) */ > bool has_chte; /* Inhibit charge (Modern firmware) */ > + bool bcf0_1byte; /* Battery critical key is 1 byte (Modern firmware) */ > > u8 num_cells; > int nominal_voltage_mv; > @@ -273,6 +274,19 @@ static int macsmc_battery_get_date(const char *s, int *out) > return 0; > } > > +static int macsmc_battery_read_bcf0(struct macsmc_power *power, u32 *val) > +{ > + u8 tval = 0; > + int ret; > + > + if (!power->bcf0_1byte) > + return apple_smc_read_u32(power->smc, SMC_KEY(BCF0), val); > + > + ret = apple_smc_read_u8(power->smc, SMC_KEY(BCF0), &tval); > + *val = tval; > + return ret; > +} I think the following is slightly easier to read { if (power->bcf0_1byte) { u8 tval = 0; int ret = apple_smc_read_u8(power->smc, SMC_KEY(BCF0), &tval); *val = tval; return ret; } return apple_smc_read_u32(power->smc, SMC_KEY(BCF0), val); } Not worth a respin in itself but worthwhile if there's a v3 for the the Fixes: tag. > + > static int macsmc_battery_get_capacity_level(struct macsmc_power *power) > { > bool flag; > @@ -280,7 +294,7 @@ static int macsmc_battery_get_capacity_level(struct macsmc_power *power) > int ret; > > /* Check for emergency shutdown condition */ > - if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val) >= 0 && val) > + if (macsmc_battery_read_bcf0(power, &val) >= 0 && val) > return POWER_SUPPLY_CAPACITY_LEVEL_CRITICAL; > > /* Check AC status for whether we could boot in this state */ > @@ -577,7 +591,7 @@ static void macsmc_power_critical_work(struct work_struct *wrk) > * Check if SMC flagged the battery as empty. > * We trigger a graceful shutdown to let the OS save data. > */ > - if (apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &bcf0) == 0 && bcf0 != 0) { > + if (macsmc_battery_read_bcf0(power, &bcf0) == 0 && bcf0 != 0) { > power->orderly_shutdown_triggered = true; > dev_crit(power->dev, "Battery critical (empty flag set). Triggering orderly shutdown.\n"); > orderly_poweroff(true); > @@ -616,6 +630,7 @@ static int macsmc_power_probe(struct platform_device *pdev) > struct device *dev = &pdev->dev; > struct apple_smc *smc = dev_get_drvdata(pdev->dev.parent); > struct power_supply_config psy_cfg = {}; > + struct apple_smc_key_info info; > struct macsmc_power *power; > bool has_battery = false; > bool has_ac_adapter = false; > @@ -714,6 +729,20 @@ static int macsmc_power_probe(struct platform_device *pdev) > if (apple_smc_key_exists(smc, SMC_KEY(CH0I))) > power->has_ch0i = true; > > + ret = apple_smc_get_key_info(power->smc, SMC_KEY(BCF0), &info); > + if (ret) { > + dev_err(&pdev->dev, "Failed to determine BCF0 key size\n"); > + return ret; > + } > + if (info.size == 1) > + power->bcf0_1byte = true; > + else if (info.size == 4) > + power->bcf0_1byte = false; > + else { > + dev_err(&pdev->dev, "Unexpected BCF0 key size %d\n", info.size); > + return -EIO; > + } > + > /* Reset "Optimised Battery Charging" flags to default state */ > if (power->has_chte) > apple_smc_write_u32(smc, SMC_KEY(CHTE), 0); > @@ -766,7 +795,7 @@ static int macsmc_power_probe(struct platform_device *pdev) > power->nominal_voltage_mv = MACSMC_NOMINAL_CELL_VOLTAGE_MV * power->num_cells; > > /* Enable critical shutdown notifications by reading status once */ > - apple_smc_read_u32(power->smc, SMC_KEY(BCF0), &val32); > + macsmc_battery_read_bcf0(power, &val32); > > psy_cfg.drv_data = power; > power->batt = devm_power_supply_register(dev, &power->batt_desc, &psy_cfg); > > --- Reviewed-by: Janne Grunau thanks Janne