linux-kernel - [PATCH v1 8/8] bus: mhi: core: Ensure non-zero session or sequence ID values

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Message-Id: <1587529175-27778-9-git-send-email-bbhatt@codeaurora.org>
Date:   Tue, 21 Apr 2020 21:19:35 -0700
From:   Bhaumik Bhatt <bbhatt@...eaurora.org>
To:     linux-arm-msm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Bhaumik Bhatt <bbhatt@...eaurora.org>
Subject: [PATCH v1 8/8] bus: mhi: core: Ensure non-zero session or sequence ID values

While writing any sequence or session identifiers, it is possible that
the host could write a zero value, whereas only non-zero values are
supported writes to those registers. Ensure that host does not write a
non-zero value for those cases.

Signed-off-by: Bhaumik Bhatt <bbhatt@...eaurora.org>
---
 drivers/bus/mhi/core/boot.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/bus/mhi/core/boot.c b/drivers/bus/mhi/core/boot.c
index 0bc9c50..c9971d4 100644
--- a/drivers/bus/mhi/core/boot.c
+++ b/drivers/bus/mhi/core/boot.c
@@ -199,6 +199,9 @@ static int mhi_fw_load_amss(struct mhi_controller *mhi_cntrl,
 	mhi_write_reg(mhi_cntrl, base, BHIE_TXVECSIZE_OFFS, mhi_buf->len);
 
 	sequence_id = prandom_u32() & BHIE_TXVECSTATUS_SEQNUM_BMSK;
+	if (unlikely(!sequence_id))
+		sequence_id = 1;
+
 	mhi_write_reg_field(mhi_cntrl, base, BHIE_TXVECDB_OFFS,
 			    BHIE_TXVECDB_SEQNUM_BMSK, BHIE_TXVECDB_SEQNUM_SHFT,
 			    sequence_id);
@@ -254,6 +257,9 @@ static int mhi_fw_load_sbl(struct mhi_controller *mhi_cntrl,
 		      lower_32_bits(dma_addr));
 	mhi_write_reg(mhi_cntrl, base, BHI_IMGSIZE, size);
 	session_id = prandom_u32() & BHI_TXDB_SEQNUM_BMSK;
+	if (unlikely(!session_id))
+		session_id = 1;
+
 	mhi_write_reg(mhi_cntrl, base, BHI_IMGTXDB, session_id);
 	read_unlock_bh(pm_lock);
 
-- 
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