Commit 4decbbc8 authored by Adrian Hunter's avatar Adrian Hunter Committed by Alexandre Belloni
Browse files

i3c: mipi-i3c-hci: Fix race in DMA ring enqueue for parallel xfers 



The I3C subsystem allows multiple transfers to be queued concurrently.
However, the MIPI I3C HCI driver's DMA enqueue path, hci_dma_queue_xfer(),
lacks sufficient serialization.

In particular, the allocation of the enqueue_ptr and its subsequent update
in the RING_OPERATION1 register, must be done atomically.  Otherwise, for
example, it would be possible for 2 transfers to be allocated the same
enqueue_ptr.

Extend the use of the existing spinlock for that purpose.  Keep a count of
the number of xfers enqueued so that it is easy to determine if the ring
has enough space.

Fixes: 9ad9a52c ("i3c/master: introduce the mipi-i3c-hci driver")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarAdrian Hunter <adrian.hunter@intel.com>
Reviewed-by: default avatarFrank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260306072451.11131-6-adrian.hunter@intel.com


Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
parent fa12bb90

drivers/i3c/master/mipi-i3c-hci/dma.c

+16 −16
Original line number Diff line number Diff line
@@ -129,7 +129,7 @@ struct hci_rh_data { 
	dma_addr_t xfer_dma, resp_dma, ibi_status_dma, ibi_data_dma;

	unsigned int xfer_entries, ibi_status_entries, ibi_chunks_total;

	unsigned int xfer_struct_sz, resp_struct_sz, ibi_status_sz, ibi_chunk_sz;

	unsigned int done_ptr, ibi_chunk_ptr;

	unsigned int done_ptr, ibi_chunk_ptr, xfer_space;

	struct hci_xfer **src_xfers;

	struct completion op_done;

};
@@ -260,6 +260,7 @@ static void hci_dma_init_rh(struct i3c_hci *hci, struct hci_rh_data *rh, int i) 


	rh->done_ptr = 0;

	rh->ibi_chunk_ptr = 0;

	rh->xfer_space = rh->xfer_entries;

}



static void hci_dma_init_rings(struct i3c_hci *hci)
@@ -470,7 +471,7 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci, 
	struct hci_rings_data *rings = hci->io_data;

	struct hci_rh_data *rh;

	unsigned int i, ring, enqueue_ptr;

	u32 op1_val, op2_val;

	u32 op1_val;

	int ret;



	ret = hci_dma_map_xfer_list(hci, rings->sysdev, xfer_list, n);
@@ -481,6 +482,14 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci, 
	ring = 0;

	rh = &rings->headers[ring];



	spin_lock_irq(&hci->lock);



	if (n > rh->xfer_space) {

		spin_unlock_irq(&hci->lock);

		hci_dma_unmap_xfer(hci, xfer_list, n);

		return -EBUSY;

	}



	op1_val = rh_reg_read(RING_OPERATION1);

	enqueue_ptr = FIELD_GET(RING_OP1_CR_ENQ_PTR, op1_val);

	for (i = 0; i < n; i++) {
@@ -518,22 +527,10 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci, 
		xfer->ring_entry = enqueue_ptr;



		enqueue_ptr = (enqueue_ptr + 1) % rh->xfer_entries;



		/*

		 * We may update the hardware view of the enqueue pointer

		 * only if we didn't reach its dequeue pointer.

		 */

		op2_val = rh_reg_read(RING_OPERATION2);

		if (enqueue_ptr == FIELD_GET(RING_OP2_CR_DEQ_PTR, op2_val)) {

			/* the ring is full */

			hci_dma_unmap_xfer(hci, xfer_list, n);

			return -EBUSY;

		}

	}



	/* take care to update the hardware enqueue pointer atomically */

	spin_lock_irq(&hci->lock);

	op1_val = rh_reg_read(RING_OPERATION1);

	rh->xfer_space -= n;



	op1_val &= ~RING_OP1_CR_ENQ_PTR;

	op1_val |= FIELD_PREP(RING_OP1_CR_ENQ_PTR, enqueue_ptr);

	rh_reg_write(RING_OPERATION1, op1_val);
@@ -601,6 +598,7 @@ static void hci_dma_xfer_done(struct i3c_hci *hci, struct hci_rh_data *rh) 
{

	u32 op1_val, op2_val, resp, *ring_resp;

	unsigned int tid, done_ptr = rh->done_ptr;

	unsigned int done_cnt = 0;

	struct hci_xfer *xfer;



	for (;;) {
@@ -632,10 +630,12 @@ static void hci_dma_xfer_done(struct i3c_hci *hci, struct hci_rh_data *rh) 


		done_ptr = (done_ptr + 1) % rh->xfer_entries;

		rh->done_ptr = done_ptr;

		done_cnt += 1;

	}



	/* take care to update the software dequeue pointer atomically */

	spin_lock(&hci->lock);

	rh->xfer_space += done_cnt;

	op1_val = rh_reg_read(RING_OPERATION1);

	op1_val &= ~RING_OP1_CR_SW_DEQ_PTR;

	op1_val |= FIELD_PREP(RING_OP1_CR_SW_DEQ_PTR, done_ptr);