Messages in this thread | | | Subject | Re: [PATCH v3] applesmc: Re-work SMC comms | From | Henrik Rydberg <> | Date | Sun, 8 Nov 2020 09:35:28 +0100 |
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Hi Brad,
On 2020-11-08 02:00, Brad Campbell wrote: > G'day Henrik, > > I noticed you'd also loosened up the requirement for SMC_STATUS_BUSY in read_smc(). I assume > that causes problems on the early Macbook. This is revised on the one sent earlier. > If you could test this on your Air1,1 it'd be appreciated.
No, I managed to screw up the patch; you can see that I carefully added the same treatment for the read argument, being unsure if the BUSY state would remain during the AVAILABLE data phase. I can check that again, but unfortunately the patch in this email shows the same problem.
I think it may be worthwhile to rethink the behavior of wait_status() here. If one machine shows no change after a certain status bit change, then perhaps the others share that behavior, and we are waiting in vain. Just imagine how many years of cpu that is, combined. ;-)
Henrik
> > 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 > > 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 : Inital attempt > v2 : Address logic and coding style > v3 : Removed some debug hangover. Added tested-by. Modifications for MacBookAir1,1 > > diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c > index a18887990f4a..3e968abb37aa 100644 > --- a/drivers/hwmon/applesmc.c > +++ b/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 > @@ -42,6 +43,11 @@ > > #define APPLESMC_MAX_DATA_LENGTH 32 > > +/* Apple SMC status bits */ > +#define SMC_STATUS_AWAITING_DATA BIT(0) /* SMC has data waiting */ > +#define SMC_STATUS_IB_CLOSED BIT(1) /* Will ignore any input */ > +#define SMC_STATUS_BUSY BIT(2) /* Command in progress */ > + > /* wait up to 128 ms for a status change. */ > #define APPLESMC_MIN_WAIT 0x0010 > #define APPLESMC_RETRY_WAIT 0x0100 > @@ -151,65 +157,73 @@ 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 and after writes, and before reads > */ > -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; > > + udelay(APPLESMC_MIN_WAIT); > for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { > - usleep_range(us, us * 16); > 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 * 16); > } > - > - pr_warn("wait_read() fail: 0x%02x\n", status); > return -EIO; > } > > /* > - * send_byte - Write to SMC port, retrying when necessary. Callers > + * send_byte_data - Write to SMC data port. Callers > * must hold applesmc_lock. > + * Parameter skip must be true on the last write of any > + * command or it'll time out. > */ > -static int send_byte(u8 cmd, u16 port) > + > +static int send_byte_data(u8 cmd, u16 port, bool skip) > { > - u8 status; > - int us; > - unsigned long end = jiffies + (APPLESMC_MAX_WAIT * HZ) / USEC_PER_SEC; > + int ret; > > + ret = wait_status(SMC_STATUS_BUSY, SMC_STATUS_BUSY | SMC_STATUS_IB_CLOSED); > + if (ret) > + return ret; > 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); > - } > + return wait_status(skip ? 0 : SMC_STATUS_BUSY, SMC_STATUS_BUSY); > +} > > - pr_warn("send_byte(0x%02x, 0x%04x) fail: 0x%02x\n", cmd, port, status); > - return -EIO; > +static int send_byte(u8 cmd, u16 port) > +{ > + return send_byte_data(cmd, port, false); > } > > +/* > + * send_command - Write a command to the SMC. Callers must hold applesmc_lock. > + * If SMC is in undefined state, any new command write resets the state machine. > + */ > + > static int send_command(u8 cmd) > { > - return send_byte(cmd, APPLESMC_CMD_PORT); > + int ret; > + int i; > + > + for (i = 0; i < 16; i++) { > + ret = wait_status(0, SMC_STATUS_IB_CLOSED); > + if (ret) > + return ret; > + > + outb(cmd, APPLESMC_CMD_PORT); > + ret = wait_status(SMC_STATUS_BUSY, SMC_STATUS_BUSY); > + if (!ret) > + return ret; > + } > + return -EIO; > } > > static int send_argument(const char *key) > @@ -239,7 +253,8 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len) > } > > for (i = 0; i < len; i++) { > - if (wait_read()) { > + if (wait_status(SMC_STATUS_AWAITING_DATA, > + SMC_STATUS_AWAITING_DATA | SMC_STATUS_IB_CLOSED)) { > pr_warn("%.4s: read data[%d] fail\n", key, i); > return -EIO; > } > @@ -250,7 +265,7 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len) > 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); > } > @@ -275,7 +290,7 @@ static int write_smc(u8 cmd, const char *key, const u8 *buffer, u8 len) > } > > for (i = 0; i < len; i++) { > - if (send_byte(buffer[i], APPLESMC_DATA_PORT)) { > + if (send_byte_data(buffer[i], APPLESMC_DATA_PORT, i == len - 1)) { > pr_warn("%s: write data fail\n", key); > return -EIO; > } >
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