linux-kernel - [PATCH 7/8] memory: brcmstb: dpfe: Compute checksum at __send

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Date:   Tue, 15 Oct 2019 15:45:12 -0700
From:   Markus Mayer <mmayer@...adcom.com>
To:     Brian Norris <computersforpeace@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Gregory Fong <gregory.0xf0@...il.com>
Cc:     Broadcom Kernel List <bcm-kernel-feedback-list@...adcom.com>,
        ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Markus Mayer <mmayer@...adcom.com>
Subject: [PATCH 7/8] memory: brcmstb: dpfe: Compute checksum at __send_command() time

From: Florian Fainelli <f.fainelli@...il.com>

Instead of pre-computing the checksum, do it at the time we send the
command, this reduces the possibility of introducing errors as well as
limits the amount of code necessary while adding new commands and/or new
API versions. The MSG_CHKSUM enumeration value is no longer necessary
and is removed.

Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: Markus Mayer <mmayer@...adcom.com>
---
 drivers/memory/brcmstb_dpfe.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/drivers/memory/brcmstb_dpfe.c b/drivers/memory/brcmstb_dpfe.c
index cf320302d2c0..7c6e85ad25a7 100644
--- a/drivers/memory/brcmstb_dpfe.c
+++ b/drivers/memory/brcmstb_dpfe.c
@@ -127,7 +127,6 @@ enum dpfe_msg_fields {
 	MSG_COMMAND,
 	MSG_ARG_COUNT,
 	MSG_ARG0,
-	MSG_CHKSUM,
 	MSG_FIELD_MAX	= 16 /* Max number of arguments */
 };
 
@@ -243,21 +242,18 @@ static const struct dpfe_api dpfe_api_v2 = {
 			[MSG_COMMAND] = 1,
 			[MSG_ARG_COUNT] = 1,
 			[MSG_ARG0] = 1,
-			[MSG_CHKSUM] = 4,
 		},
 		[DPFE_CMD_GET_REFRESH] = {
 			[MSG_HEADER] = DPFE_MSG_TYPE_COMMAND,
 			[MSG_COMMAND] = 2,
 			[MSG_ARG_COUNT] = 1,
 			[MSG_ARG0] = 1,
-			[MSG_CHKSUM] = 5,
 		},
 		[DPFE_CMD_GET_VENDOR] = {
 			[MSG_HEADER] = DPFE_MSG_TYPE_COMMAND,
 			[MSG_COMMAND] = 2,
 			[MSG_ARG_COUNT] = 1,
 			[MSG_ARG0] = 2,
-			[MSG_CHKSUM] = 6,
 		},
 	}
 };
@@ -273,18 +269,11 @@ static const struct dpfe_api dpfe_api_v3 = {
 			[MSG_COMMAND] = 0x0101,
 			[MSG_ARG_COUNT] = 1,
 			[MSG_ARG0] = 1,
-			[MSG_CHKSUM] = 0x104,
 		},
 		[DPFE_CMD_GET_REFRESH] = {
 			[MSG_HEADER] = DPFE_MSG_TYPE_COMMAND,
 			[MSG_COMMAND] = 0x0202,
 			[MSG_ARG_COUNT] = 0,
-			/*
-			 * This is a bit ugly. Without arguments, the checksum
-			 * follows right after the argument count and not at
-			 * offset MSG_CHKSUM.
-			 */
-			[MSG_ARG0] = 0x203,
 		},
 		/* There's no GET_VENDOR command in API v3. */
 	},
@@ -432,9 +421,17 @@ static int __send_command(struct brcmstb_dpfe_priv *priv, unsigned int cmd,
 		return -ETIMEDOUT;
 	}
 
+	/* Compute checksum over the message */
+	chksum_idx = msg[MSG_ARG_COUNT] + MSG_ARG_COUNT + 1;
+	chksum = get_msg_chksum(msg, chksum_idx);
+
 	/* Write command and arguments to message area */
-	for (i = 0; i < MSG_FIELD_MAX; i++)
-		writel_relaxed(msg[i], regs + DCPU_MSG_RAM(i));
+	for (i = 0; i < MSG_FIELD_MAX; i++) {
+		if (i == chksum_idx)
+			writel_relaxed(chksum, regs + DCPU_MSG_RAM(i));
+		else
+			writel_relaxed(msg[i], regs + DCPU_MSG_RAM(i));
+	}
 
 	/* Tell DCPU there is a command waiting */
 	writel_relaxed(1, regs + REG_TO_DCPU_MBOX);
-- 
2.17.1