Re: [PATCH v7 2/2] Input: add Apple SPI keyboard and trackpad driver.

Life is hard, and then you die
2019-07-17T10:24:53Z

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Hi Dmitry,

thanks for taking a look at this!

On Tue, Jul 16, 2019 at 08:47:44PM +0200, Dmitry Torokhov wrote:
> Hi Ronald,
>
> On Fri, Apr 19, 2019 at 01:19:26AM -0700, Ronald Tschalär wrote:
> > The keyboard and trackpad on recent MacBook's (since 8,1) and
> > MacBookPro's (13,* and 14,*) are attached to an SPI controller instead
> > of USB, as previously. The higher level protocol is not publicly
> > documented and hence has been reverse engineered. As a consequence there
> > are still a number of unknown fields and commands. However, the known
> > parts have been working well and received extensive testing and use.
> >
> > In order for this driver to work, the proper SPI drivers need to be
> > loaded too; for MB8,1 these are spi_pxa2xx_platform and spi_pxa2xx_pci;
> > for all others they are spi_pxa2xx_platform and intel_lpss_pci. For this
> > reason enabling this driver in the config implies enabling the above
> > drivers.
>
> I applied the patch (but changed __u8 to u8 as that's preferred form for
> inside the kernel, and added error handling for input_mt_init_slots) but
> we need to do some more work on the driver.

Looks good.

> My main issue is with registering touchpad device asynchronously,
> independent from the probe() function. This means (as far as I can tell)
> that any error is not really appropriately handled (as by that time it
> is too late to signal errors from probe()) and devm functions are not
> going to be called, leaving remnants of the resources in memory on
> driver unload. It also brings in issues with suspend/resume (what
> happens if you suspend really quickly while device is not registered
> yet?), etc, etc.

Yes, the lack of error propagation also bothered me a bit when I
introduced the dev-info command, but I thought doing synchronous
I/O operations in a probe function wasn't kosher. Happy to rectify
that though.

> Can we switch to calling DEV_INFO command synchronously from probe()? If
> we are concerned about it taking relatively long time we can always
> annotate the driver as having probe_type = PROBE_PREFER_ASYNCHRONOUS so
> that other devices can be probed simultaneously with applespi.

Normally the dev-info retrieval takes about 15ms - I presume that's
fast enough?

Attached is a patch that does this now (on top of your changes above).
The cancelling of outstanding spi requests in the error case is a bit
ugly (I wish there were an exported spi-flush/spi-wait-for-queue-empty
function or similar), but otherwise it's fairly straightforward.

Cheers,

Ronald

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From a03a7b42ac6ea0707165c8beba04c722984064be Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ronald=20Tschal=C3=A4r?= <ronald@innovation.ch>
Date: Wed, 17 Jul 2019 02:46:57 -0700
Subject: [PATCH] Input: applespi - register touchpad device synchronously in
probe.
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

This allows errors during registration to properly fail the probe
function.

Doing this requires waiting for a response from the device inside the
probe function. While this generally takes about 15ms, in case of errors
it could be arbitrarily long, and hence a 3 second timeout is used.

This also adds 3 second timeouts to the drain functions to avoid the
potential for suspend or remove hanging forever.

Signed-off-by: Ronald Tschalär <ronald@innovation.ch>
---
drivers/input/keyboard/applespi.c | 125 ++++++++++++++++++++++++------
1 file changed, 100 insertions(+), 25 deletions(-)

diff --git a/drivers/input/keyboard/applespi.c b/drivers/input/keyboard/applespi.c
index 548737e7aeda..81a733a6ba1a 100644
--- a/drivers/input/keyboard/applespi.c
+++ b/drivers/input/keyboard/applespi.c
@@ -48,12 +48,12 @@
#include <linux/efi.h>
#include <linux/input.h>
#include <linux/input/mt.h>
+#include <linux/jiffies.h>
#include <linux/leds.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/spi/spi.h>
#include <linux/wait.h>
-#include <linux/workqueue.h>

#include <asm/barrier.h>
#include <asm/unaligned.h>
@@ -411,7 +411,13 @@ struct applespi_data {
bool read_active;
bool write_active;

- struct work_struct work;
+ struct applespi_complete_info {
+ void (*complete)(void *context);
+ struct applespi_data *applespi;
+ } spi_complete[2];
+ bool cancel_spi;
+
+ wait_queue_head_t tp_info_complete;
struct touchpad_info_protocol rcvd_tp_info;

struct dentry *debugfs_root;
@@ -593,13 +599,61 @@ static void applespi_setup_write_txfrs(struct applespi_data *applespi)
spi_message_add_tail(st_t, msg);
}

+static bool applespi_async_outstanding(struct applespi_data *applespi)
+{
+ return applespi->spi_complete[0].complete ||
+ applespi->spi_complete[1].complete;
+}
+
+static void applespi_async_complete(void *context)
+{
+ struct applespi_complete_info *info = context;
+ struct applespi_data *applespi = info->applespi;
+ unsigned long flags;
+
+ info->complete(applespi);
+
+ spin_lock_irqsave(&applespi->cmd_msg_lock, flags);
+
+ info->complete = NULL;
+
+ if (applespi->cancel_spi && !applespi_async_outstanding(applespi))
+ wake_up_all(&applespi->drain_complete);
+
+ spin_unlock_irqrestore(&applespi->cmd_msg_lock, flags);
+}
+
static int applespi_async(struct applespi_data *applespi,
struct spi_message *message, void (*complete)(void *))
{
- message->complete = complete;
- message->context = applespi;
+ struct applespi_complete_info *info;
+ int sts;
+
+ if (applespi->cancel_spi) {
+ if (!applespi_async_outstanding(applespi))
+ wake_up_all(&applespi->drain_complete);
+ return -ESHUTDOWN;
+ }
+
+ /*
+ * There can only be at max 2 spi requests in flight, one for "reads"
+ * and one for "writes".
+ */
+ if (!applespi->spi_complete[0].complete)
+ info = &applespi->spi_complete[0];
+ else
+ info = &applespi->spi_complete[1];
+ info->complete = complete;
+ info->applespi = applespi;
+
+ message->complete = applespi_async_complete;
+ message->context = info;
+
+ sts = spi_async(applespi->spi, message);
+ if (sts)
+ info->complete = NULL;

- return spi_async(applespi->spi, message);
+ return sts;
}

static inline bool applespi_check_write_status(struct applespi_data *applespi,
@@ -664,6 +718,7 @@ static int applespi_setup_spi(struct applespi_data *applespi)

spin_lock_init(&applespi->cmd_msg_lock);
init_waitqueue_head(&applespi->drain_complete);
+ init_waitqueue_head(&applespi->tp_info_complete);

return 0;
}
@@ -1011,7 +1066,7 @@ static void report_tp_state(struct applespi_data *applespi,
const struct applespi_tp_info *tp_info = &applespi->tp_info;
int i, n;

- /* touchpad_input_dev is set async in worker */
+ /* touchpad_input_dev is set async in probe */
input = smp_load_acquire(&applespi->touchpad_input_dev);
if (!input)
return; /* touchpad isn't initialized yet */
@@ -1315,26 +1370,14 @@ applespi_register_touchpad_device(struct applespi_data *applespi,
return 0;
}

-static void applespi_worker(struct work_struct *work)
-{
- struct applespi_data *applespi =
- container_of(work, struct applespi_data, work);
-
- applespi_register_touchpad_device(applespi, &applespi->rcvd_tp_info);
-}
-
static void applespi_handle_cmd_response(struct applespi_data *applespi,
struct spi_packet *packet,
struct message *message)
{
if (packet->device == PACKET_DEV_INFO &&
le16_to_cpu(message->type) == 0x1020) {
- /*
- * We're not allowed to sleep here, but registering an input
- * device can sleep.
- */
applespi->rcvd_tp_info = message->tp_info;
- schedule_work(&applespi->work);
+ wake_up_all(&applespi->tp_info_complete);
return;
}

@@ -1623,6 +1666,7 @@ static int applespi_probe(struct spi_device *spi)
struct applespi_data *applespi;
acpi_handle spi_handle = ACPI_HANDLE(&spi->dev);
acpi_status acpi_sts;
+ unsigned long flags;
int sts, i;
unsigned long long gpe, usb_status;

@@ -1641,8 +1685,6 @@ static int applespi_probe(struct spi_device *spi)

applespi->spi = spi;

- INIT_WORK(&applespi->work, applespi_worker);
-
/* store the driver data */
spi_set_drvdata(spi, applespi);

@@ -1770,6 +1812,22 @@ static int applespi_probe(struct spi_device *spi)
/* trigger touchpad setup */
applespi_init(applespi, false);

+ /* set up the touchpad as a separate input device */
+ sts = wait_event_timeout(applespi->tp_info_complete,
+ applespi->rcvd_tp_info.model_no,
+ msecs_to_jiffies(3000));
+ if (!sts) {
+ dev_err(&applespi->spi->dev,
+ "Timed out waiting for device info\n");
+ sts = -ETIMEDOUT;
+ goto cancel_spi;
+ }
+
+ sts = applespi_register_touchpad_device(applespi,
+ &applespi->rcvd_tp_info);
+ if (sts)
+ goto cancel_spi;
+
/*
* By default this device is not enabled for wakeup; but USB keyboards
* generally are, so the expectation is that by default the keyboard
@@ -1820,6 +1878,19 @@ static int applespi_probe(struct spi_device *spi)
}

return 0;
+
+cancel_spi:
+ acpi_disable_gpe(NULL, applespi->gpe);
+ acpi_remove_gpe_handler(NULL, applespi->gpe, applespi_notify);
+
+ spin_lock_irqsave(&applespi->cmd_msg_lock, flags);
+ applespi->cancel_spi = true;
+ wait_event_lock_irq(applespi->drain_complete,
+ !applespi_async_outstanding(applespi),
+ applespi->cmd_msg_lock);
+ spin_unlock_irqrestore(&applespi->cmd_msg_lock, flags);
+
+ return sts;
}

static void applespi_drain_writes(struct applespi_data *applespi)
@@ -1829,8 +1900,10 @@ static void applespi_drain_writes(struct applespi_data *applespi)
spin_lock_irqsave(&applespi->cmd_msg_lock, flags);

applespi->drain = true;
- wait_event_lock_irq(applespi->drain_complete, !applespi->write_active,
- applespi->cmd_msg_lock);
+ wait_event_lock_irq_timeout(applespi->drain_complete,
+ !applespi->write_active,
+ applespi->cmd_msg_lock,
+ msecs_to_jiffies(3000));

spin_unlock_irqrestore(&applespi->cmd_msg_lock, flags);
}
@@ -1841,8 +1914,10 @@ static void applespi_drain_reads(struct applespi_data *applespi)

spin_lock_irqsave(&applespi->cmd_msg_lock, flags);

- wait_event_lock_irq(applespi->drain_complete, !applespi->read_active,
- applespi->cmd_msg_lock);
+ wait_event_lock_irq_timeout(applespi->drain_complete,
+ !applespi->read_active,
+ applespi->cmd_msg_lock,
+ msecs_to_jiffies(3000));

applespi->suspended = true;

--
2.21.0