[PATCH v2] HID: intel-thc-hid: intel-quickspi: reset touch IC on system resume

[d3z <d3z.the.dev@gmail.com>]

From: Danny D. <d3z.the.dev@gmail.com>

On the Surface Pro 10 (Meteor Lake) the touchscreen stops working after a
suspend/resume cycle and only recovers after a reboot. The driver logs
"GET_DEVICE_INFO: recv failed: -11" on resume.

This platform suspends through s2idle: /sys/power/mem_sleep exposes
"[s2idle]" as the only state, there is no "deep"/S3 entry at all. The
touch IC nonetheless loses power across that s2idle suspend, the same
way it does across hibernation. quickspi_resume() only re-selects the
THC port, restores interrupts and DMA and sends a HIDSPI_ON command,
assuming the touch IC kept its power and state. When it has actually
lost power the HIDSPI_ON command is never acknowledged and the
descriptor read fails, leaving the touchscreen dead until the module is
reloaded.

quickspi_restore() already handles this for hibernation by
reconfiguring the THC SPI/LTR settings and running reset_tic() to
re-enumerate the device. Make quickspi_resume() do the same when the
device is not a wake source. A wake-enabled device keeps its power and
state across suspend, so it stays on the light restore path: resetting
it would discard a pending wake touch event and break wake-on-touch.

The non-wake path mirrors the existing quickspi_restore() sequence,
including enabling interrupts before reset_tic(), so it introduces no
new ordering relative to code already in the driver.

This change has been validated on a Surface Pro 10 running the
linux-surface kernel across multiple s2idle suspend/resume cycles; it
has not been tested on a mainline build.

Closes: https://github.com/linux-surface/linux-surface/issues/1799
Signed-off-by: Danny D. <d3z.the.dev@gmail.com>
---
v1 -> v2:
 - Only run the full reset when the device is not a wake source
   (device_may_wakeup()), so wake-on-touch is no longer disturbed.
 - Reword the changelog around s2idle: the SP10 has no "deep"/S3 state, the
   touch IC loses power across s2idle.

 .../hid/intel-thc-hid/intel-quickspi/pci-quickspi.c | 60 +++++++++++++++++--
 1 file changed, 56 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c b/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c
--- a/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c
+++ b/drivers/hid/intel-thc-hid/intel-quickspi/pci-quickspi.c
@@ -784,20 +784,72 @@ static int quickspi_resume(struct device
 	if (ret)
 		return ret;
 
+	/*
+	 * A wake-enabled device keeps its power and state across suspend, so
+	 * only restore the THC context. Resetting it here would discard a
+	 * pending wake touch event and break wake-on-touch.
+	 */
+	if (device_may_wakeup(qsdev->dev)) {
+		thc_interrupt_config(qsdev->thc_hw);
+
+		thc_interrupt_enable(qsdev->thc_hw, true);
+
+		ret = thc_dma_configure(qsdev->thc_hw);
+		if (ret)
+			return ret;
+
+		return thc_interrupt_quiesce(qsdev->thc_hw, false);
+	}
+
+	/*
+	 * Otherwise the touch IC may have lost power across suspend. On
+	 * platforms that suspend through s2idle (for example the Surface Pro
+	 * 10, whose firmware exposes s2idle as the only mem_sleep state) the
+	 * IC loses power the same way it does across hibernation. A plain
+	 * HIDSPI_ON is then not acknowledged and the descriptor read fails, so
+	 * re-enumerate the device through the full reset flow already used by
+	 * quickspi_restore().
+	 */
+	thc_spi_input_output_address_config(qsdev->thc_hw,
+					    qsdev->input_report_hdr_addr,
+					    qsdev->input_report_bdy_addr,
+					    qsdev->output_report_addr);
+
+	ret = thc_spi_read_config(qsdev->thc_hw, qsdev->spi_freq_val,
+				  qsdev->spi_read_io_mode,
+				  qsdev->spi_read_opcode,
+				  qsdev->spi_packet_size);
+	if (ret)
+		return ret;
+
+	ret = thc_spi_write_config(qsdev->thc_hw, qsdev->spi_freq_val,
+				   qsdev->spi_write_io_mode,
+				   qsdev->spi_write_opcode,
+				   qsdev->spi_packet_size,
+				   qsdev->performance_limit);
+	if (ret)
+		return ret;
+
 	thc_interrupt_config(qsdev->thc_hw);
 
 	thc_interrupt_enable(qsdev->thc_hw, true);
 
-	ret = thc_dma_configure(qsdev->thc_hw);
+	/* The touch IC may have lost power, reset it to recover */
+	ret = reset_tic(qsdev);
 	if (ret)
 		return ret;
 
-	ret = thc_interrupt_quiesce(qsdev->thc_hw, false);
+	ret = thc_dma_configure(qsdev->thc_hw);
 	if (ret)
 		return ret;
 
-	if (!device_may_wakeup(qsdev->dev))
-		return quickspi_set_power(qsdev, HIDSPI_ON);
+	thc_ltr_config(qsdev->thc_hw,
+		       qsdev->active_ltr_val,
+		       qsdev->low_power_ltr_val);
+
+	thc_change_ltr_mode(qsdev->thc_hw, THC_LTR_MODE_ACTIVE);
+
+	qsdev->state = QUICKSPI_ENABLED;
 
 	return 0;
 }
-- 
2.43.0