| Message ID | 194a7d71-a781-765a-d177-c962ef296b90@fnarfbargle.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v6,1/1] applesmc: Re-work SMC comms | expand |
On 11/11/20 7:08 PM, Brad Campbell wrote: > Commit fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") > introduced an issue whereby communication with the SMC became > unreliable with write errors like : > > [ 120.378614] applesmc: send_byte(0x00, 0x0300) fail: 0x40 > [ 120.378621] applesmc: LKSB: write data fail > [ 120.512782] applesmc: send_byte(0x00, 0x0300) fail: 0x40 > [ 120.512787] applesmc: LKSB: write data fail > > The original code appeared to be timing sensitive and was not reliable > with the timing changes in the aforementioned commit. > > This patch re-factors the SMC communication to remove the timing > dependencies and restore function with the changes previously > committed. > > Tested on : MacbookAir6,2 MacBookPro11,1 iMac12,2, MacBookAir1,1, > MacBookAir3,1 > > Fixes: fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") > Reported-by: Andreas Kemnade <andreas@kemnade.info> > Tested-by: Andreas Kemnade <andreas@kemnade.info> # MacBookAir6,2 > Acked-by: Arnd Bergmann <arnd@arndb.de> > Signed-off-by: Brad Campbell <brad@fnarfbargle.com> > Signed-off-by: Henrik Rydberg <rydberg@bitmath.org> Applied. Guenter > > --- > Changelog : > v1 : Initial attempt > v2 : Address logic and coding style based on comments received > v3 : Removed some debug hangover. Added tested-by. Modifications for MacBookAir1,1 > - Significant rework of wait logic by Henrik Rydberg <rydberg@bitmath.org> to > make it function at all on the MacBookAir1,1. > > v4 : Re-factored logic based on Apple driver. Simplified wait_status loop > - Re-factored the logic again, this time based on the Apple driver. This > functioned without error on all tested Macs. wait_status() contributed > by Henrik Rydberg <rydberg@bitmath.org> > > v5 : Re-wrote status loop. Simplified busy check in send_byte() > - Re-wrote wait_status() based on feedback from Guenter Roeck <linux@roeck-us.net> > - Added additional comments to explain multiple tests in send_byte() > - Addressed repeated indentation issues > > v6 : Reverted simplification of busy check in send_byte() > - The logic simplification in v5 send_byte() caused a few read failures in > stress testing on a fast SMC (3 in 5.6million). Reverting that change passed > 5 million reads with 0 errors. > > Index: linux-stable/drivers/hwmon/applesmc.c > =================================================================== > --- linux-stable.orig/drivers/hwmon/applesmc.c > +++ linux-stable/drivers/hwmon/applesmc.c > @@ -32,6 +32,7 @@ > #include <linux/hwmon.h> > #include <linux/workqueue.h> > #include <linux/err.h> > +#include <linux/bits.h> > > /* data port used by Apple SMC */ > #define APPLESMC_DATA_PORT 0x300 > @@ -42,10 +43,13 @@ > > #define APPLESMC_MAX_DATA_LENGTH 32 > > -/* wait up to 128 ms for a status change. */ > -#define APPLESMC_MIN_WAIT 0x0010 > -#define APPLESMC_RETRY_WAIT 0x0100 > -#define APPLESMC_MAX_WAIT 0x20000 > +/* Apple SMC status bits */ > +#define SMC_STATUS_AWAITING_DATA BIT(0) /* SMC has data waiting to be read */ > +#define SMC_STATUS_IB_CLOSED BIT(1) /* Will ignore any input */ > +#define SMC_STATUS_BUSY BIT(2) /* Command in progress */ > + > +/* Initial wait is 8us */ > +#define APPLESMC_MIN_WAIT 0x0008 > > #define APPLESMC_READ_CMD 0x10 > #define APPLESMC_WRITE_CMD 0x11 > @@ -151,65 +155,84 @@ static unsigned int key_at_index; > static struct workqueue_struct *applesmc_led_wq; > > /* > - * wait_read - Wait for a byte to appear on SMC port. Callers must > - * hold applesmc_lock. > + * Wait for specific status bits with a mask on the SMC. > + * Used before all transactions. > + * This does 10 fast loops of 8us then exponentially backs off for a > + * minimum total wait of 262ms. Depending on usleep_range this could > + * run out past 500ms. > */ > -static int wait_read(void) > + > +static int wait_status(u8 val, u8 mask) > { > - unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; > u8 status; > int us; > + int i; > > - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { > - usleep_range(us, us * 16); > + us = APPLESMC_MIN_WAIT; > + for (i = 0; i < 24 ; i++) { > status = inb(APPLESMC_CMD_PORT); > - /* read: wait for smc to settle */ > - if (status & 0x01) > + if ((status & mask) == val) > return 0; > - /* timeout: give up */ > - if (time_after(jiffies, end)) > - break; > + usleep_range(us, us * 2); > + if (i > 9) > + us <<= 1; > } > - > - pr_warn("wait_read() fail: 0x%02x\n", status); > return -EIO; > } > > -/* > - * send_byte - Write to SMC port, retrying when necessary. Callers > - * must hold applesmc_lock. > - */ > +/* send_byte - Write to SMC data port. Callers must hold applesmc_lock. */ > + > static int send_byte(u8 cmd, u16 port) > { > - u8 status; > - int us; > - unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; > + int status; > > - outb(cmd, port); > - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { > - usleep_range(us, us * 16); > - status = inb(APPLESMC_CMD_PORT); > - /* write: wait for smc to settle */ > - if (status & 0x02) > - continue; > - /* ready: cmd accepted, return */ > - if (status & 0x04) > - return 0; > - /* timeout: give up */ > - if (time_after(jiffies, end)) > - break; > - /* busy: long wait and resend */ > - udelay(APPLESMC_RETRY_WAIT); > - outb(cmd, port); > - } > + status = wait_status(0, SMC_STATUS_IB_CLOSED); > + if (status) > + return status; > + /* > + * This needs to be a separate read looking for bit 0x04 > + * after bit 0x02 falls. If consolidated with the wait above > + * this extra read may not happen if status returns both > + * simultaneously and this would appear to be required. > + */ > + status = wait_status(SMC_STATUS_BUSY, SMC_STATUS_BUSY); > + if (status) > + return status; > > - pr_warn("send_byte(0x%02x, 0x%04x) fail: 0x%02x\n", cmd, port, status); > - return -EIO; > + outb(cmd, port); > + return 0; > } > > +/* send_command - Write a command to the SMC. Callers must hold applesmc_lock. */ > + > static int send_command(u8 cmd) > { > - return send_byte(cmd, APPLESMC_CMD_PORT); > + int ret; > + > + ret = wait_status(0, SMC_STATUS_IB_CLOSED); > + if (ret) > + return ret; > + outb(cmd, APPLESMC_CMD_PORT); > + return 0; > +} > + > +/* > + * Based on logic from the Apple driver. This is issued before any interaction > + * If busy is stuck high, issue a read command to reset the SMC state machine. > + * If busy is stuck high after the command then the SMC is jammed. > + */ > + > +static int smc_sane(void) > +{ > + int ret; > + > + ret = wait_status(0, SMC_STATUS_BUSY); > + if (!ret) > + return ret; > + ret = send_command(APPLESMC_READ_CMD); > + if (ret) > + return ret; > + return wait_status(0, SMC_STATUS_BUSY); > } > > static int send_argument(const char *key) > @@ -226,6 +249,11 @@ static int read_smc(u8 cmd, const char * > { > u8 status, data = 0; > int i; > + int ret; > + > + ret = smc_sane(); > + if (ret) > + return ret; > > if (send_command(cmd) || send_argument(key)) { > pr_warn("%.4s: read arg fail\n", key); > @@ -239,7 +267,8 @@ static int read_smc(u8 cmd, const char * > } > > for (i = 0; i < len; i++) { > - if (wait_read()) { > + if (wait_status(SMC_STATUS_AWAITING_DATA | SMC_STATUS_BUSY, > + SMC_STATUS_AWAITING_DATA | SMC_STATUS_BUSY)) { > pr_warn("%.4s: read data[%d] fail\n", key, i); > return -EIO; > } > @@ -250,19 +279,24 @@ static int read_smc(u8 cmd, const char * > for (i = 0; i < 16; i++) { > udelay(APPLESMC_MIN_WAIT); > status = inb(APPLESMC_CMD_PORT); > - if (!(status & 0x01)) > + if (!(status & SMC_STATUS_AWAITING_DATA)) > break; > data = inb(APPLESMC_DATA_PORT); > } > if (i) > pr_warn("flushed %d bytes, last value is: %d\n", i, data); > > - return 0; > + return wait_status(0, SMC_STATUS_BUSY); > } > > static int write_smc(u8 cmd, const char *key, const u8 *buffer, u8 len) > { > int i; > + int ret; > + > + ret = smc_sane(); > + if (ret) > + return ret; > > if (send_command(cmd) || send_argument(key)) { > pr_warn("%s: write arg fail\n", key); > @@ -281,7 +315,7 @@ static int write_smc(u8 cmd, const char > } > } > > - return 0; > + return wait_status(0, SMC_STATUS_BUSY); > } > > static int read_register_count(unsigned int *count) >
Index: linux-stable/drivers/hwmon/applesmc.c =================================================================== --- linux-stable.orig/drivers/hwmon/applesmc.c +++ linux-stable/drivers/hwmon/applesmc.c @@ -32,6 +32,7 @@ #include <linux/hwmon.h> #include <linux/workqueue.h> #include <linux/err.h> +#include <linux/bits.h> /* data port used by Apple SMC */ #define APPLESMC_DATA_PORT 0x300 @@ -42,10 +43,13 @@ #define APPLESMC_MAX_DATA_LENGTH 32 -/* wait up to 128 ms for a status change. */ -#define APPLESMC_MIN_WAIT 0x0010 -#define APPLESMC_RETRY_WAIT 0x0100 -#define APPLESMC_MAX_WAIT 0x20000 +/* Apple SMC status bits */ +#define SMC_STATUS_AWAITING_DATA BIT(0) /* SMC has data waiting to be read */ +#define SMC_STATUS_IB_CLOSED BIT(1) /* Will ignore any input */ +#define SMC_STATUS_BUSY BIT(2) /* Command in progress */ + +/* Initial wait is 8us */ +#define APPLESMC_MIN_WAIT 0x0008 #define APPLESMC_READ_CMD 0x10 #define APPLESMC_WRITE_CMD 0x11 @@ -151,65 +155,84 @@ static unsigned int key_at_index; static struct workqueue_struct *applesmc_led_wq; /* - * wait_read - Wait for a byte to appear on SMC port. Callers must - * hold applesmc_lock. + * Wait for specific status bits with a mask on the SMC. + * Used before all transactions. + * This does 10 fast loops of 8us then exponentially backs off for a + * minimum total wait of 262ms. Depending on usleep_range this could + * run out past 500ms. */ -static int wait_read(void) + +static int wait_status(u8 val, u8 mask) { - unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; u8 status; int us; + int i; - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { - usleep_range(us, us * 16); + us = APPLESMC_MIN_WAIT; + for (i = 0; i < 24 ; i++) { status = inb(APPLESMC_CMD_PORT); - /* read: wait for smc to settle */ - if (status & 0x01) + if ((status & mask) == val) return 0; - /* timeout: give up */ - if (time_after(jiffies, end)) - break; + usleep_range(us, us * 2); + if (i > 9) + us <<= 1; } - - pr_warn("wait_read() fail: 0x%02x\n", status); return -EIO; } -/* - * send_byte - Write to SMC port, retrying when necessary. Callers - * must hold applesmc_lock. - */ +/* send_byte - Write to SMC data port. Callers must hold applesmc_lock. */ + static int send_byte(u8 cmd, u16 port) { - u8 status; - int us; - unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; + int status; - outb(cmd, port); - for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { - usleep_range(us, us * 16); - status = inb(APPLESMC_CMD_PORT); - /* write: wait for smc to settle */ - if (status & 0x02) - continue; - /* ready: cmd accepted, return */ - if (status & 0x04) - return 0; - /* timeout: give up */ - if (time_after(jiffies, end)) - break; - /* busy: long wait and resend */ - udelay(APPLESMC_RETRY_WAIT); - outb(cmd, port); - } + status = wait_status(0, SMC_STATUS_IB_CLOSED); + if (status) + return status; + /* + * This needs to be a separate read looking for bit 0x04 + * after bit 0x02 falls. If consolidated with the wait above + * this extra read may not happen if status returns both + * simultaneously and this would appear to be required. + */ + status = wait_status(SMC_STATUS_BUSY, SMC_STATUS_BUSY); + if (status) + return status; - pr_warn("send_byte(0x%02x, 0x%04x) fail: 0x%02x\n", cmd, port, status); - return -EIO; + outb(cmd, port); + return 0; } +/* send_command - Write a command to the SMC. Callers must hold applesmc_lock. */ + static int send_command(u8 cmd) { - return send_byte(cmd, APPLESMC_CMD_PORT); + int ret; + + ret = wait_status(0, SMC_STATUS_IB_CLOSED); + if (ret) + return ret; + outb(cmd, APPLESMC_CMD_PORT); + return 0; +} + +/* + * Based on logic from the Apple driver. This is issued before any interaction + * If busy is stuck high, issue a read command to reset the SMC state machine. + * If busy is stuck high after the command then the SMC is jammed. + */ + +static int smc_sane(void) +{ + int ret; + + ret = wait_status(0, SMC_STATUS_BUSY); + if (!ret) + return ret; + ret = send_command(APPLESMC_READ_CMD); + if (ret) + return ret; + return wait_status(0, SMC_STATUS_BUSY); } static int send_argument(const char *key) @@ -226,6 +249,11 @@ static int read_smc(u8 cmd, const char * { u8 status, data = 0; int i; + int ret; + + ret = smc_sane(); + if (ret) + return ret; if (send_command(cmd) || send_argument(key)) { pr_warn("%.4s: read arg fail\n", key); @@ -239,7 +267,8 @@ static int read_smc(u8 cmd, const char * } for (i = 0; i < len; i++) { - if (wait_read()) { + if (wait_status(SMC_STATUS_AWAITING_DATA | SMC_STATUS_BUSY, + SMC_STATUS_AWAITING_DATA | SMC_STATUS_BUSY)) { pr_warn("%.4s: read data[%d] fail\n", key, i); return -EIO; } @@ -250,19 +279,24 @@ static int read_smc(u8 cmd, const char * for (i = 0; i < 16; i++) { udelay(APPLESMC_MIN_WAIT); status = inb(APPLESMC_CMD_PORT); - if (!(status & 0x01)) + if (!(status & SMC_STATUS_AWAITING_DATA)) break; data = inb(APPLESMC_DATA_PORT); } if (i) pr_warn("flushed %d bytes, last value is: %d\n", i, data); - return 0; + return wait_status(0, SMC_STATUS_BUSY); } static int write_smc(u8 cmd, const char *key, const u8 *buffer, u8 len) { int i; + int ret; + + ret = smc_sane(); + if (ret) + return ret; if (send_command(cmd) || send_argument(key)) { pr_warn("%s: write arg fail\n", key); @@ -281,7 +315,7 @@ static int write_smc(u8 cmd, const char } } - return 0; + return wait_status(0, SMC_STATUS_BUSY); } static int read_register_count(unsigned int *count)
Commit fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") introduced an issue whereby communication with the SMC became unreliable with write errors like : [ 120.378614] applesmc: send_byte(0x00, 0x0300) fail: 0x40 [ 120.378621] applesmc: LKSB: write data fail [ 120.512782] applesmc: send_byte(0x00, 0x0300) fail: 0x40 [ 120.512787] applesmc: LKSB: write data fail The original code appeared to be timing sensitive and was not reliable with the timing changes in the aforementioned commit. This patch re-factors the SMC communication to remove the timing dependencies and restore function with the changes previously committed. Tested on : MacbookAir6,2 MacBookPro11,1 iMac12,2, MacBookAir1,1, MacBookAir3,1 Fixes: fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") Reported-by: Andreas Kemnade <andreas@kemnade.info> Tested-by: Andreas Kemnade <andreas@kemnade.info> # MacBookAir6,2 Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Brad Campbell <brad@fnarfbargle.com> Signed-off-by: Henrik Rydberg <rydberg@bitmath.org> --- Changelog : v1 : Initial attempt v2 : Address logic and coding style based on comments received v3 : Removed some debug hangover. Added tested-by. Modifications for MacBookAir1,1 - Significant rework of wait logic by Henrik Rydberg <rydberg@bitmath.org> to make it function at all on the MacBookAir1,1. v4 : Re-factored logic based on Apple driver. Simplified wait_status loop - Re-factored the logic again, this time based on the Apple driver. This functioned without error on all tested Macs. wait_status() contributed by Henrik Rydberg <rydberg@bitmath.org> v5 : Re-wrote status loop. Simplified busy check in send_byte() - Re-wrote wait_status() based on feedback from Guenter Roeck <linux@roeck-us.net> - Added additional comments to explain multiple tests in send_byte() - Addressed repeated indentation issues v6 : Reverted simplification of busy check in send_byte() - The logic simplification in v5 send_byte() caused a few read failures in stress testing on a fast SMC (3 in 5.6million). Reverting that change passed 5 million reads with 0 errors.