* Re: [PATCH] applesmc: Re-work SMC comms v1
@ 2020-11-05 6:32 Guenter Roeck
0 siblings, 0 replies; 3+ messages in thread
From: Guenter Roeck @ 2020-11-05 6:32 UTC (permalink / raw)
To: Brad Campbell
Cc: Andreas Kemnade, Jean Delvare, Arnd Bergmann, rydberg,
linux-hwmon, linux-kernel, hns
On Thu, Nov 05, 2020 at 04:47:25PM +1100, Brad Campbell wrote:
> Commit fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") introduced
> an issue whereby communication with the SMC became unreliable with write
> errors :
>
> [ 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.
>
> Reported-by: Andreas Kemnade <andreas@kemnade.info>
Add
Fixes: fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()")
> Signed-off-by: Brad Campbell <brad@fnarfbargle.com>
>
> ---
> diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
> index a18887990f4a..22cc5122ce9a 100644
> --- a/drivers/hwmon/applesmc.c
> +++ b/drivers/hwmon/applesmc.c
> @@ -42,6 +42,11 @@
>
> #define APPLESMC_MAX_DATA_LENGTH 32
>
> +/* Apple SMC status bits from VirtualSMC */
> +#define SMC_STATUS_AWAITING_DATA 0x01 ///< Data waiting to be read
> +#define SMC_STATUS_IB_CLOSED 0x02 /// A write is pending / will ignore input
> +#define SMC_STATUS_BUSY 0x04 ///< Busy in the middle of a command.
> +
Maybe consider using BIT() while at it.
/* Please use standard comments */
Also, what does the "<" mean ? Is that supposed to be negated
(ie bit set means not busy) ? If so, that isn't a standard notation
that I am aware of. Maybe "not set if busy in the middle of a command"
would be better in this case.
> /* wait up to 128 ms for a status change. */
> #define APPLESMC_MIN_WAIT 0x0010
> #define APPLESMC_RETRY_WAIT 0x0100
> @@ -151,65 +156,77 @@ 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;
>
> 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;
> - }
> -
> - pr_warn("wait_read() fail: 0x%02x\n", status);
> + usleep_range(us, us * 16);
> + }
> + pr_warn("wait_status timeout: 0x%02x, 0x%02x, 0x%02x\n", status, val, mask);
> 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)
I would suggest to keep send_byte() and change it to the following.
static int send_byte(u8 cmd, u16 port)
{
return send_byte_data(cmd, port, false);
}
That would limit the number of changes needed later in the code
(it is never called with a hard 'true' as parameter).
> +
> +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;
> + u8 wstat = SMC_STATUS_BUSY;
>
> + if (skip)
> + wstat = 0;
u8 wstat = skip ? 0 : SMC_STATUS_BUSY;
> + if (wait_status(SMC_STATUS_BUSY,
> + SMC_STATUS_BUSY | SMC_STATUS_IB_CLOSED))
This fits one line, and the error code
should really not be overwritten.
ret = wait_status(SMC_STATUS_BUSY, SMC_STATUS_BUSY | SMC_STATUS_IB_CLOSED);
if (ret)
return ret;
> + goto fail;
> 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);
> - }
> -
> - pr_warn("send_byte(0x%02x, 0x%04x) fail: 0x%02x\n", cmd, port, status);
> + if (!wait_status(wstat,
> + SMC_STATUS_BUSY))
That really fits into one line.
> + return 0;
> +fail:
> + pr_warn("send_byte_data(0x%02x, 0x%04x) fail\n", cmd, APPLESMC_CMD_PORT);
Can you drop this message ? wait_status() already displays a message,
after all. Also, please reverse error handling, and don't overwrite
error codes.
ret = wait_status(wstat, SMC_STATUS_BUSY)
if (ret)
return ret;
Actually, this can be simplified to
return wait_status(wstat, SMC_STATUS_BUSY);
or, since wstat is only used once,
return wait_status(skip ? 0 : SMC_STATUS_BUSY, SMC_STATUS_BUSY);
> return -EIO;
> }
>
> +/*
> + * 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);
> + u8 status;
> +
> + if (wait_status(0,
> + SMC_STATUS_IB_CLOSED)) {
Another one of those odd continuation lines.
> + pr_warn("send_command SMC was busy\n");
and logging noise. As for error handling, same as above, please
ret = wait_status(0, SMC_STATUS_IB_CLOSED);
if (ret)
return ret;
> + goto fail; }
> +
> + status = inb(APPLESMC_CMD_PORT);
> +
> + outb(cmd, APPLESMC_CMD_PORT);
> + if (!wait_status(SMC_STATUS_BUSY,
> + SMC_STATUS_BUSY))
Odd/unnecessary continuation line again.
> + return 0;
> +fail:
> + pr_warn("send_cmd(0x%02x, 0x%04x) fail\n", cmd, APPLESMC_CMD_PORT);
Wow, up to three messages on failure. Please, don't do that.
One message per failure is really enough. Please simplify to
return wait_status(SMC_STATUS_BUSY, SMC_STATUS_BUSY);
Actually, I notice that the callers of send_command()
log yet again. Maybe it is time to drop all the messages
from here and from send_argument() and only log in the
calling code.
> + return -EIO;
> }
>
> static int send_argument(const char *key)
> @@ -217,7 +234,8 @@ static int send_argument(const char *key)
> int i;
>
> for (i = 0; i < 4; i++)
> - if (send_byte(key[i], APPLESMC_DATA_PORT))
> + /* Parameter skip is false as we always send data after an argument */
Please align comments with code. Maybe move the comment ahead
of the for statement. Or drop it entirely - it doesn't add that
much value. Actually, this blob would go away if you keep
send_byte().
> + if (send_byte_data(key[i], APPLESMC_DATA_PORT, false))
> return -EIO;
> return 0;
> }
> @@ -233,13 +251,15 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len)
> }
>
> /* This has no effect on newer (2012) SMCs */
> - if (send_byte(len, APPLESMC_DATA_PORT)) {
> + if (send_byte_data(len, APPLESMC_DATA_PORT, false)) {
> pr_warn("%.4s: read len fail\n", key);
> return -EIO;
> }
>
> 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 |
> + SMC_STATUS_IB_CLOSED)) {
Align continuatiuon lines with preceding '('. "checkpatch --strict"
reports all those alignment issues.
> pr_warn("%.4s: read data[%d] fail\n", key, i);
> return -EIO;
> }
> @@ -250,7 +270,7 @@ 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);
> }
> @@ -263,20 +283,21 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len)
> static int write_smc(u8 cmd, const char *key, const u8 *buffer, u8 len)
> {
> int i;
> + u8 end = len-1;
space before and after '-', please. checkpatch --strict will tell.
>
> if (send_command(cmd) || send_argument(key)) {
> pr_warn("%s: write arg fail\n", key);
> return -EIO;
I notice the driver keeps overwriting error codes. Oh well.
I can't expect you to fix that, and it should not be fixed as part
of this patch, but please don't make it worse (not here, but above
where calls are changed).
> }
>
> - if (send_byte(len, APPLESMC_DATA_PORT)) {
> + if (send_byte_data(len, APPLESMC_DATA_PORT, false)) {
> pr_warn("%.4s: write len fail\n", key);
> return -EIO;
> }
>
> for (i = 0; i < len; i++) {
> - if (send_byte(buffer[i], APPLESMC_DATA_PORT)) {
> - pr_warn("%s: write data fail\n", key);
> + if (send_byte_data(buffer[i], APPLESMC_DATA_PORT, (i == end))) {
Unnecessary ( ) around i == end. Not sure if the 'end' variable
is worth it. Might as well make it "i == len - 1" and let the compiler
optimize it at will.
> + pr_warn("%s: write data fail at %i\n", key, i);
> return -EIO;
> }
> }
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] applesmc: Re-work SMC comms v1
2020-11-05 5:47 ` [PATCH] applesmc: Re-work SMC comms v1 Brad Campbell
@ 2020-11-09 9:27 ` kernel test robot
0 siblings, 0 replies; 3+ messages in thread
From: kernel test robot @ 2020-11-09 9:27 UTC (permalink / raw)
To: Brad Campbell, Guenter Roeck, Andreas Kemnade, Jean Delvare
Cc: kbuild-all, Arnd Bergmann, rydberg, linux-hwmon, linux-kernel, hns
[-- Attachment #1: Type: text/plain, Size: 2339 bytes --]
Hi Brad,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on hwmon/hwmon-next]
[also build test WARNING on v5.10-rc3 next-20201109]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Brad-Campbell/applesmc-Re-work-SMC-comms-v1/20201105-134944
base: https://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging.git hwmon-next
config: i386-randconfig-r022-20201109 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce (this is a W=1 build):
# https://github.com/0day-ci/linux/commit/db5e9737dcc2fec2ff3713bc346904d4b5ac5c0d
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Brad-Campbell/applesmc-Re-work-SMC-comms-v1/20201105-134944
git checkout db5e9737dcc2fec2ff3713bc346904d4b5ac5c0d
# save the attached .config to linux build tree
make W=1 ARCH=i386
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All warnings (new ones prefixed by >>):
drivers/hwmon/applesmc.c: In function 'send_command':
>> drivers/hwmon/applesmc.c:214:5: warning: variable 'status' set but not used [-Wunused-but-set-variable]
214 | u8 status;
| ^~~~~~
vim +/status +214 drivers/hwmon/applesmc.c
206
207 /*
208 * send_command - Write a command to the SMC. Callers must hold applesmc_lock.
209 * If SMC is in undefined state, any new command write resets the state machine.
210 */
211
212 static int send_command(u8 cmd)
213 {
> 214 u8 status;
215
216 if (wait_status(0,
217 SMC_STATUS_IB_CLOSED)) {
218 pr_warn("send_command SMC was busy\n");
219 goto fail; }
220
221 status = inb(APPLESMC_CMD_PORT);
222
223 outb(cmd, APPLESMC_CMD_PORT);
224 if (!wait_status(SMC_STATUS_BUSY,
225 SMC_STATUS_BUSY))
226 return 0;
227 fail:
228 pr_warn("send_cmd(0x%02x, 0x%04x) fail\n", cmd, APPLESMC_CMD_PORT);
229 return -EIO;
230 }
231
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
[-- Attachment #2: .config.gz --]
[-- Type: application/gzip, Size: 40374 bytes --]
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH] applesmc: Re-work SMC comms v1
2020-11-05 5:26 ` Guenter Roeck
@ 2020-11-05 5:47 ` Brad Campbell
2020-11-09 9:27 ` kernel test robot
0 siblings, 1 reply; 3+ messages in thread
From: Brad Campbell @ 2020-11-05 5:47 UTC (permalink / raw)
To: Guenter Roeck, Andreas Kemnade, Jean Delvare
Cc: Arnd Bergmann, rydberg, linux-hwmon, linux-kernel, hns
Commit fff2d0f701e6 ("hwmon: (applesmc) avoid overlong udelay()") introduced
an issue whereby communication with the SMC became unreliable with write
errors :
[ 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.
Reported-by: Andreas Kemnade <andreas@kemnade.info>
Signed-off-by: Brad Campbell <brad@fnarfbargle.com>
---
diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
index a18887990f4a..22cc5122ce9a 100644
--- a/drivers/hwmon/applesmc.c
+++ b/drivers/hwmon/applesmc.c
@@ -42,6 +42,11 @@
#define APPLESMC_MAX_DATA_LENGTH 32
+/* Apple SMC status bits from VirtualSMC */
+#define SMC_STATUS_AWAITING_DATA 0x01 ///< Data waiting to be read
+#define SMC_STATUS_IB_CLOSED 0x02 /// A write is pending / will ignore input
+#define SMC_STATUS_BUSY 0x04 ///< Busy in the middle of a command.
+
/* wait up to 128 ms for a status change. */
#define APPLESMC_MIN_WAIT 0x0010
#define APPLESMC_RETRY_WAIT 0x0100
@@ -151,65 +156,77 @@ 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;
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;
- }
-
- pr_warn("wait_read() fail: 0x%02x\n", status);
+ usleep_range(us, us * 16);
+ }
+ pr_warn("wait_status timeout: 0x%02x, 0x%02x, 0x%02x\n", status, val, mask);
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;
+ u8 wstat = SMC_STATUS_BUSY;
+ if (skip)
+ wstat = 0;
+ if (wait_status(SMC_STATUS_BUSY,
+ SMC_STATUS_BUSY | SMC_STATUS_IB_CLOSED))
+ goto fail;
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);
- }
-
- pr_warn("send_byte(0x%02x, 0x%04x) fail: 0x%02x\n", cmd, port, status);
+ if (!wait_status(wstat,
+ SMC_STATUS_BUSY))
+ return 0;
+fail:
+ pr_warn("send_byte_data(0x%02x, 0x%04x) fail\n", cmd, APPLESMC_CMD_PORT);
return -EIO;
}
+/*
+ * 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);
+ u8 status;
+
+ if (wait_status(0,
+ SMC_STATUS_IB_CLOSED)) {
+ pr_warn("send_command SMC was busy\n");
+ goto fail; }
+
+ status = inb(APPLESMC_CMD_PORT);
+
+ outb(cmd, APPLESMC_CMD_PORT);
+ if (!wait_status(SMC_STATUS_BUSY,
+ SMC_STATUS_BUSY))
+ return 0;
+fail:
+ pr_warn("send_cmd(0x%02x, 0x%04x) fail\n", cmd, APPLESMC_CMD_PORT);
+ return -EIO;
}
static int send_argument(const char *key)
@@ -217,7 +234,8 @@ static int send_argument(const char *key)
int i;
for (i = 0; i < 4; i++)
- if (send_byte(key[i], APPLESMC_DATA_PORT))
+ /* Parameter skip is false as we always send data after an argument */
+ if (send_byte_data(key[i], APPLESMC_DATA_PORT, false))
return -EIO;
return 0;
}
@@ -233,13 +251,15 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len)
}
/* This has no effect on newer (2012) SMCs */
- if (send_byte(len, APPLESMC_DATA_PORT)) {
+ if (send_byte_data(len, APPLESMC_DATA_PORT, false)) {
pr_warn("%.4s: read len fail\n", key);
return -EIO;
}
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 |
+ SMC_STATUS_IB_CLOSED)) {
pr_warn("%.4s: read data[%d] fail\n", key, i);
return -EIO;
}
@@ -250,7 +270,7 @@ 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);
}
@@ -263,20 +283,21 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len)
static int write_smc(u8 cmd, const char *key, const u8 *buffer, u8 len)
{
int i;
+ u8 end = len-1;
if (send_command(cmd) || send_argument(key)) {
pr_warn("%s: write arg fail\n", key);
return -EIO;
}
- if (send_byte(len, APPLESMC_DATA_PORT)) {
+ if (send_byte_data(len, APPLESMC_DATA_PORT, false)) {
pr_warn("%.4s: write len fail\n", key);
return -EIO;
}
for (i = 0; i < len; i++) {
- if (send_byte(buffer[i], APPLESMC_DATA_PORT)) {
- pr_warn("%s: write data fail\n", key);
+ if (send_byte_data(buffer[i], APPLESMC_DATA_PORT, (i == end))) {
+ pr_warn("%s: write data fail at %i\n", key, i);
return -EIO;
}
}
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2020-11-09 9:28 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-11-05 6:32 [PATCH] applesmc: Re-work SMC comms v1 Guenter Roeck
-- strict thread matches above, loose matches on Subject: below --
2020-09-30 8:54 [REGRESSION] hwmon: (applesmc) avoid overlong udelay() Andreas Kemnade
2020-09-30 16:44 ` Guenter Roeck
2020-09-30 20:00 ` Arnd Bergmann
2020-10-01 22:22 ` Andreas Kemnade
2020-10-02 4:07 ` Guenter Roeck
2020-10-06 7:02 ` Andreas Kemnade
2020-11-02 23:56 ` Brad Campbell
2020-11-03 5:56 ` Brad Campbell
2020-11-04 13:20 ` Andreas Kemnade
2020-11-05 2:18 ` Brad Campbell
2020-11-05 4:43 ` Guenter Roeck
2020-11-05 5:05 ` Brad Campbell
2020-11-05 5:26 ` Guenter Roeck
2020-11-05 5:47 ` [PATCH] applesmc: Re-work SMC comms v1 Brad Campbell
2020-11-09 9:27 ` kernel test robot
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