From e9d28020d267fc76aa261537c0114d4402d678da Mon Sep 17 00:00:00 2001 From: Bin Meng Date: Sat, 23 Jan 2021 18:39:56 +0800 Subject: hw/sd: sd: Drop sd_crc16() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit f6fb1f9b319f ("sdcard: Correct CRC16 offset in sd_function_switch()") changed the 16-bit CRC to be stored at offset 64. In fact, this CRC calculation is completely wrong. From the original codes, it wants to calculate the CRC16 of the first 64 bytes of sd->data[], however passing 64 as the `width` to sd_crc16() actually counts 256 bytes starting from the `message` for the CRC16 calculation, which is not what we want. Besides that, it seems existing sd_crc16() algorithm does not match the SD spec, which says CRC16 is the CCITT one but the calculation does not produce expected result. It turns out the CRC16 was never transferred outside the sd core, as in sd_read_byte() we see: if (sd->data_offset >= 64) sd->state = sd_transfer_state; Given above reasons, let's drop it. Signed-off-by: Bin Meng Tested-by: Pragnesh Patel Reviewed-by: Pragnesh Patel Reviewed-by: Philippe Mathieu-Daudé Message-Id: <20210123104016.17485-6-bmeng.cn@gmail.com> Signed-off-by: Philippe Mathieu-Daudé --- hw/sd/sd.c | 18 ------------------ 1 file changed, 18 deletions(-) (limited to 'hw/sd') diff --git a/hw/sd/sd.c b/hw/sd/sd.c index bfea5547d5..b3952514fe 100644 --- a/hw/sd/sd.c +++ b/hw/sd/sd.c @@ -271,23 +271,6 @@ static uint8_t sd_crc7(const void *message, size_t width) return shift_reg; } -static uint16_t sd_crc16(const void *message, size_t width) -{ - int i, bit; - uint16_t shift_reg = 0x0000; - const uint16_t *msg = (const uint16_t *)message; - width <<= 1; - - for (i = 0; i < width; i ++, msg ++) - for (bit = 15; bit >= 0; bit --) { - shift_reg <<= 1; - if ((shift_reg >> 15) ^ ((*msg >> bit) & 1)) - shift_reg ^= 0x1011; - } - - return shift_reg; -} - #define OCR_POWER_DELAY_NS 500000 /* 0.5ms */ FIELD(OCR, VDD_VOLTAGE_WINDOW, 0, 24) @@ -843,7 +826,6 @@ static void sd_function_switch(SDState *sd, uint32_t arg) sd->data[16 - (i >> 1)] |= new_func << ((i % 2) * 4); } memset(&sd->data[17], 0, 47); - stw_be_p(sd->data + 64, sd_crc16(sd->data, 64)); } static inline bool sd_wp_addr(SDState *sd, uint64_t addr) -- cgit v1.2.3