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Subject[PATCH 2/2] platform/chrome: reserve only the I/O ports required for the MEC EC
Date
Some ChromeOS EC devices (such as the Framework Laptop) only map I/O
ports 0x800-0x807. Making the larger reservation required by the non-MEC
LPC (the 0xFF ports for the memory map, and the 0xFF ports for the
parameter region) is non-viable on these devices.

Since we probe the MEC EC first, we can get away with a smaller
reservation that covers the MEC EC ports. If we fall back to classic
LPC, we can grow the reservation to cover the memory map and the
parameter region.

Signed-off-by: Dustin L. Howett <dustin@howett.net>
---
drivers/platform/chrome/cros_ec_lpc.c | 39 ++++++++++++-------
.../linux/platform_data/cros_ec_commands.h | 4 ++
2 files changed, 30 insertions(+), 13 deletions(-)

diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c
index 458eb59db2ff..06fdfe365710 100644
--- a/drivers/platform/chrome/cros_ec_lpc.c
+++ b/drivers/platform/chrome/cros_ec_lpc.c
@@ -341,9 +341,14 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
u8 buf[2];
int irq, ret;

- if (!devm_request_region(dev, EC_LPC_ADDR_MEMMAP, EC_MEMMAP_SIZE,
- dev_name(dev))) {
- dev_err(dev, "couldn't reserve memmap region\n");
+ /*
+ * The Framework Laptop (and possibly other non-ChromeOS devices)
+ * only exposes the eight I/O ports that are required for the Microchip EC.
+ * Requesting a larger reservation will fail.
+ */
+ if (!devm_request_region(dev, EC_HOST_CMD_REGION0,
+ EC_HOST_CMD_MEC_REGION_SIZE, dev_name(dev))) {
+ dev_err(dev, "couldn't reserve MEC region\n");
return -EBUSY;
}

@@ -357,6 +362,12 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
cros_ec_lpc_ops.write = cros_ec_lpc_mec_write_bytes;
cros_ec_lpc_ops.read(EC_LPC_ADDR_MEMMAP + EC_MEMMAP_ID, 2, buf);
if (buf[0] != 'E' || buf[1] != 'C') {
+ if (!devm_request_region(dev, EC_LPC_ADDR_MEMMAP, EC_MEMMAP_SIZE,
+ dev_name(dev))) {
+ dev_err(dev, "couldn't reserve memmap region\n");
+ return -EBUSY;
+ }
+
/* Re-assign read/write operations for the non MEC variant */
cros_ec_lpc_ops.read = cros_ec_lpc_read_bytes;
cros_ec_lpc_ops.write = cros_ec_lpc_write_bytes;
@@ -366,17 +377,19 @@ static int cros_ec_lpc_probe(struct platform_device *pdev)
dev_err(dev, "EC ID not detected\n");
return -ENODEV;
}
- }

- if (!devm_request_region(dev, EC_HOST_CMD_REGION0,
- EC_HOST_CMD_REGION_SIZE, dev_name(dev))) {
- dev_err(dev, "couldn't reserve region0\n");
- return -EBUSY;
- }
- if (!devm_request_region(dev, EC_HOST_CMD_REGION1,
- EC_HOST_CMD_REGION_SIZE, dev_name(dev))) {
- dev_err(dev, "couldn't reserve region1\n");
- return -EBUSY;
+ /* Reserve the remaining I/O ports required by the non-MEC protocol. */
+ if (!devm_request_region(dev, EC_HOST_CMD_REGION0 + EC_HOST_CMD_MEC_REGION_SIZE,
+ EC_HOST_CMD_REGION_SIZE - EC_HOST_CMD_MEC_REGION_SIZE,
+ dev_name(dev))) {
+ dev_err(dev, "couldn't reserve remainder of region0\n");
+ return -EBUSY;
+ }
+ if (!devm_request_region(dev, EC_HOST_CMD_REGION1,
+ EC_HOST_CMD_REGION_SIZE, dev_name(dev))) {
+ dev_err(dev, "couldn't reserve region1\n");
+ return -EBUSY;
+ }
}

ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
diff --git a/include/linux/platform_data/cros_ec_commands.h b/include/linux/platform_data/cros_ec_commands.h
index 271bd87bff0a..a85b1176e6c0 100644
--- a/include/linux/platform_data/cros_ec_commands.h
+++ b/include/linux/platform_data/cros_ec_commands.h
@@ -55,6 +55,10 @@
#define EC_HOST_CMD_REGION0 0x800
#define EC_HOST_CMD_REGION1 0x880
#define EC_HOST_CMD_REGION_SIZE 0x80
+/*
+ * Other machines report only the region spanned by the Microchip MEC EC.
+ */
+#define EC_HOST_CMD_MEC_REGION_SIZE 0x08

/* EC command register bit functions */
#define EC_LPC_CMDR_DATA BIT(0) /* Data ready for host to read */
--
2.34.1
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