Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753705AbcLGCKd (ORCPT ); Tue, 6 Dec 2016 21:10:33 -0500 Received: from mail-oi0-f65.google.com ([209.85.218.65]:34045 "EHLO mail-oi0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753115AbcLGCJm (ORCPT ); Tue, 6 Dec 2016 21:09:42 -0500 From: Chris Bostic To: robh+dt@kernel.org, mark.rutland@arm.com, linux@armlinux.org.uk, gregkh@linuxfoundation.org, sre@kernel.org, mturquette@baylibre.com, geert+renesas@glider.be, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org Cc: Jeremy Kerr , joel@jms.id.au, linux-kernel@vger.kernel.org, andrew@aj.id.au, alistair@popple.id.au, benh@kernel.crashing.org, Chris Bostic Subject: [PATCH 08/16] drivers/fsi: Add crc4 helpers Date: Tue, 6 Dec 2016 20:09:31 -0600 Message-Id: <1481076574-54711-2-git-send-email-christopher.lee.bostic@gmail.com> X-Mailer: git-send-email 2.7.4 (Apple Git-66) In-Reply-To: <1481076574-54711-1-git-send-email-christopher.lee.bostic@gmail.com> References: <1481076574-54711-1-git-send-email-christopher.lee.bostic@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2362 Lines: 79 From: Jeremy Kerr Add some helpers for the crc checks for the slave configuration table. This works 4-bits-at-a-time, using a simple table approach. We will need this in the FSI core code, as well as any master implementations that need to calculate CRCs in software. Signed-off-by: Jeremy Kerr Signed-off-by: Chris Bostic --- drivers/fsi/fsi-core.c | 21 +++++++++++++++++++++ drivers/fsi/fsi-master.h | 21 +++++++++++++++++++++ 2 files changed, 42 insertions(+) diff --git a/drivers/fsi/fsi-core.c b/drivers/fsi/fsi-core.c index ceaf536..f0832c7 100644 --- a/drivers/fsi/fsi-core.c +++ b/drivers/fsi/fsi-core.c @@ -32,6 +32,27 @@ struct fsi_slave { #define to_fsi_slave(d) container_of(d, struct fsi_slave, dev) +/* crc helpers */ +static const uint8_t crc4_tab[] = { + 0x0, 0x7, 0xe, 0x9, 0xb, 0xc, 0x5, 0x2, + 0x1, 0x6, 0xf, 0x8, 0xa, 0xd, 0x4, 0x3, +}; + +uint8_t fsi_crc4(uint8_t c, uint64_t x, int bits) +{ + int i; + + /* Align to 4-bits */ + bits = (bits + 3) & ~0x3; + + /* Calculate crc4 over four-bit nibbles, starting at the MSbit */ + for (i = bits; i >= 0; i -= 4) + c = crc4_tab[c ^ ((x >> i) & 0xf)]; + + return c; +} +EXPORT_SYMBOL_GPL(fsi_crc4); + /* FSI slave support */ static int fsi_slave_init(struct fsi_master *master, int link, uint8_t slave_id) diff --git a/drivers/fsi/fsi-master.h b/drivers/fsi/fsi-master.h index e75a810..cafb433 100644 --- a/drivers/fsi/fsi-master.h +++ b/drivers/fsi/fsi-master.h @@ -34,4 +34,25 @@ struct fsi_master { extern int fsi_master_register(struct fsi_master *master); extern void fsi_master_unregister(struct fsi_master *master); +/** + * crc4 helper: Given a starting crc4 state @c, calculate the crc4 vaue of @x, + * which is @bits in length. This may be required by master implementations + * that do not provide their own hardware checksums. + * + * The crc4 is performed on 4-bit chunks (which is all we need for FSI + * calculations). Typically, we'll want a starting state of 0: + * + * c = fsi_crc4(0, msg, len); + * + * To crc4 a message that includes a single start bit, initialise crc4 state + * with: + * + * c = fsi_crc4(0, 1, 1); + * + * Then update with message data: + * + * c = fsi_crc4(c, msg, len); + */ +uint8_t fsi_crc4(uint8_t c, uint64_t x, int bits); + #endif /* DRIVERS_FSI_MASTER_H */ -- 1.8.2.2