[PATCH V2 13/17] i3c: mipi-i3c-hci: Remove invalid transfer size limit

[Adrian Hunter]

The driver derives a maximum transfer size from
HC_CAP_MAX_DATA_LENGTH in HC_CAPABILITIES, but no published version of
the I3C HCI specification defines such a field.

HC_CAPABILITIES reserves Bits[31:8] in HCI v1.0 and Bits[27:22] in HCI
v1.1 and v1.2, so the bits used by HC_CAP_MAX_DATA_LENGTH are reserved
in all released HCI versions.  Neither the HCI nor the I3C TCRI
specifications define a maximum data length capability.

On compliant controllers reserved bits read as zero, making the
computed limit 65536 bytes.  Since struct i3c_xfer.len is u16,
transfers can never reach that size and the resulting -EFBIG check can
never trigger.

Remove the unused capability definition and the dead size check.

The driver's effective limit remains unchanged. HCI specifications
define DATA_LENGTH as a 16-bit field and require larger transfers to be
split across multiple Transfer Descriptors.  The driver already relies
on the core's 16-bit length types elsewhere when constructing
descriptors.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Reviewed-by: Frank Li <Frank.Li@xxxxxxx>
---


Changes in V2:

	Added Frank Li's Reviewed-by tag.


 drivers/i3c/master/mipi-i3c-hci/core.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
index b9b20797d045..4629a16debc9 100644
--- a/drivers/i3c/master/mipi-i3c-hci/core.c
+++ b/drivers/i3c/master/mipi-i3c-hci/core.c
@@ -51,7 +51,6 @@
 #define HC_CAP_SG_DC_EN			BIT(30)
 #define HC_CAP_SG_IBI_EN		BIT(29)
 #define HC_CAP_SG_CR_EN			BIT(28)
-#define HC_CAP_MAX_DATA_LENGTH		GENMASK(24, 22)
 #define HC_CAP_CMD_SIZE			GENMASK(21, 20)
 #define HC_CAP_DIRECT_COMMANDS_EN	BIT(18)
 #define HC_CAP_MULTI_LANE_EN		BIT(15)
@@ -473,7 +472,6 @@ static int i3c_hci_i3c_xfers(struct i3c_dev_desc *dev,
 	struct i3c_hci *hci = to_i3c_hci(m);
 	struct hci_xfer *xfer;
 	DECLARE_COMPLETION_ONSTACK(done);
-	unsigned int size_limit;
 	int i, last, ret = 0;
 
 	dev_dbg(&hci->master.dev, "nxfers = %d", nxfers);
@@ -482,13 +480,8 @@ static int i3c_hci_i3c_xfers(struct i3c_dev_desc *dev,
 	if (!xfer)
 		return -ENOMEM;
 
-	size_limit = 1U << (16 + FIELD_GET(HC_CAP_MAX_DATA_LENGTH, hci->caps));
-
 	for (i = 0; i < nxfers; i++) {
 		xfer[i].data_len = i3c_xfers[i].len;
-		ret = -EFBIG;
-		if (xfer[i].data_len >= size_limit)
-			goto out;
 		xfer[i].rnw = i3c_xfers[i].rnw;
 		if (i3c_xfers[i].rnw) {
 			xfer[i].data = i3c_xfers[i].data.in;
-- 
2.53.0