platform/chrome: cros_ec_lpcs: reserve the MEC LPC I/O ports first

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.

cros_ec_lpc_probe also interacted with I/O ports 0x800-0x807 without a
reservation. Restructuring the code to request the MEC LPC region first
obviates the need to do so.

Signed-off-by: Dustin L. Howett <dustin@howett.net>
Signed-off-by: Tzung-Bi Shih <tzungbi@kernel.org>
Link: https://lore.kernel.org/r/20220217165930.15081-3-dustin@howett.net

diff --git a/drivers/platform/chrome/cros_ec_lpc.c b/drivers/platform/chrome/cros_ec_lpc.c
index 1ec12d1..8eeef85 100644 (file)
--- 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 c235545..8cfa8cf 100644 (file)
--- a/include/linux/platform_data/cros_ec_commands.h
+++ b/include/linux/platform_data/cros_ec_commands.h
@@ -51,10 +51,14 @@
 /*
  * The actual block is 0x800-0x8ff, but some BIOSes think it's 0x880-0x8ff
  * and they tell the kernel that so we have to think of it as two parts.
+ *
+ * Other BIOSes report only the I/O port region spanned by the Microchip
+ * MEC series EC; an attempt to address a larger region may fail.
  */
-#define EC_HOST_CMD_REGION0    0x800
-#define EC_HOST_CMD_REGION1    0x880
-#define EC_HOST_CMD_REGION_SIZE 0x80
+#define EC_HOST_CMD_REGION0       0x800
+#define EC_HOST_CMD_REGION1       0x880
+#define EC_HOST_CMD_REGION_SIZE    0x80
+#define EC_HOST_CMD_MEC_REGION_SIZE 0x8
 
 /* EC command register bit functions */
 #define EC_LPC_CMDR_DATA       BIT(0)  /* Data ready for host to read */