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Date: Sat, 7 Nov 2020 10:11:09 +1100
From: Brad Campbell <brad@...rfbargle.com>
To: Henrik Rydberg <rydberg@...math.org>
Cc: Arnd Bergmann <arnd@...db.de>, linux-hwmon@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
hns@...delico.com, Guenter Roeck <linux@...ck-us.net>,
Andreas Kemnade <andreas@...nade.info>,
Jean Delvare <jdelvare@...e.com>
Subject: Re: [PATCH] applesmc: Re-work SMC comms v2
On 7/11/20 3:26 am, Henrik Rydberg wrote:
>>> I can't guarantee it won't break older machines which is why I've asked for help testing it. I only have a MacbookPro 11,1 and an iMac 12,2. It fixes both of those.
>>>
>>> Help testing would be much appreciated.
>>
>> I see, this makes much more sense. I may be able to run some tests tonight. Meanwhile, looking at the patch, the status variable in send_command looks superfluous now that there is a wait_status() before it.
>
> Ok, it took some time to get the machines up to speed, but so far I have managed to run some tests on an MacBookAir1,1. I only managed to upgrade up to 4.15, so I had to revert the inputdev polling patch, but the rest applied without problems. I recovered an old test program I used to use (attached), and checked for failures and reads per second
>
> *** hwmon: (applesmc) switch to using input device polling mode
>
> At this point in the tree, with this reverted, I see 0 failures and 55 reads per second.
>
> *** hwmon: (applesmc) avoid overlong udelay()
>
> With this applied, I see 0 failures and 16 reads per second.
>
> *** hwmon: (applesmc) check status earlier.
>
> With this applied, I see 0 failures and 16 reads per second.
>
> *** (HEAD -> stable) applesmc: Re-work SMC comms v2
>
> With this applied, the kernel hangs in module probe, and the kernel log is flooded with read failures.
>
> So as it stands, it does not work at all. I will continue to check another machine, and see if I can get something working.
>
> Henrik
G'day Heinrik,
If you could try this earlier version which still had all the failure logging it in we might be able to get a handle on the failure.
Regards,
Brad
---
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;
}
}
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