[v2,5/7] Input: synaptics-rmi4 - don't do unaligned reads in IRQ context

Commit Message

Caleb Connolly Oct. 15, 2023, 9:11 p.m. UTC

From: methanal <[e-mail]>

Some replacement displays include third-party touch ICs which incur a
significant penalty (1-2 seconds) when doing certain unaligned reads.
This is enough to break functionality when it happens in the hot path,
so adjust the interrupt handler to not read from an unaligned address.

Signed-off-by: methanal <[e-mail]>
Signed-off-by: Caleb Connolly <[e-mail]>
---
This solution does wind up doing the unaligned reads on the CPU instead,
although I'm not sure how significant of a penalty this is in practise.
---
 drivers/input/rmi4/rmi_driver.c | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

Patch

diff --git a/drivers/input/rmi4/rmi_driver.c b/drivers/input/rmi4/rmi_driver.c
index cd3e4e77ab9b..22f0b35bb70b 100644
--- a/drivers/input/rmi4/rmi_driver.c
+++ b/drivers/input/rmi4/rmi_driver.c
@@ -136,9 +136,14 @@  static int rmi_process_interrupt_requests(struct rmi_device *rmi_dev)
 		return 0;
 
 	if (!data->attn_data.data) {
+		/*
+		 * Read the device status register as well and ignore it.
+		 * Some aftermarket ICs have issues with interrupt requests
+		 * otherwise.
+		 */
 		error = rmi_read_block(rmi_dev,
-				data->f01_container->fd.data_base_addr + 1,
-				data->irq_status, data->num_of_irq_regs);
+				data->f01_container->fd.data_base_addr,
+				(u8*)data->irq_status - 1, data->num_of_irq_regs + 1);
 		if (error < 0) {
 			dev_err(dev, "Failed to read irqs, code=%d\n", error);
 			return error;
@@ -1083,16 +1088,17 @@  int rmi_probe_interrupts(struct rmi_driver_data *data)
 	data->num_of_irq_regs = (data->irq_count + 7) / 8;
 
 	size = BITS_TO_LONGS(data->irq_count) * sizeof(unsigned long);
-	data->irq_memory = devm_kcalloc(dev, size, 4, GFP_KERNEL);
+	data->irq_memory = devm_kzalloc(dev, size * 4 + 1, GFP_KERNEL);
 	if (!data->irq_memory) {
 		dev_err(dev, "Failed to allocate memory for irq masks.\n");
 		return -ENOMEM;
 	}
 
-	data->irq_status	= data->irq_memory + size * 0;
-	data->fn_irq_bits	= data->irq_memory + size * 1;
-	data->current_irq_mask	= data->irq_memory + size * 2;
-	data->new_irq_mask	= data->irq_memory + size * 3;
+	/* The first byte is reserved for the device status register */
+	data->irq_status	= data->irq_memory + size * 0 + 1;
+	data->fn_irq_bits	= data->irq_memory + size * 1 + 1;
+	data->current_irq_mask	= data->irq_memory + size * 2 + 1;
+	data->new_irq_mask	= data->irq_memory + size * 3 + 1;
 
 	return retval;
 }