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| author | Miao Yan <yanmiaobest@gmail.com> | 2016-05-22 19:37:16 -0700 |
|---|---|---|
| committer | Bin Meng <bmeng.cn@gmail.com> | 2016-05-23 15:18:00 +0800 |
| commit | 331ba7db6c19992b9800e9c53373d31794ce11ae (patch) | |
| tree | e97cd2ce0ed184b3264ce09aa4749c1134d9cf3c /arch/x86 | |
| parent | 2e82e745a4cf6bad10d9fe5a53db6592f40ff903 (diff) | |
| download | blackbird-obmc-uboot-331ba7db6c19992b9800e9c53373d31794ce11ae.tar.gz blackbird-obmc-uboot-331ba7db6c19992b9800e9c53373d31794ce11ae.zip | |
x86: qemu: add comment about qfw register endianness
This patch adds some comments about qfw register endianness for clarity.
Signed-off-by: Miao Yan <yanmiaobest@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/cpu/qemu/qemu.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/cpu/qemu/qemu.c b/arch/x86/cpu/qemu/qemu.c index 6ff99474bf..c29add39b2 100644 --- a/arch/x86/cpu/qemu/qemu.c +++ b/arch/x86/cpu/qemu/qemu.c @@ -17,6 +17,7 @@ static bool i440fx; #ifdef CONFIG_QFW +/* on x86, the qfw registers are all IO ports */ #define FW_CONTROL_PORT 0x510 #define FW_DATA_PORT 0x511 #define FW_DMA_PORT_LOW 0x514 @@ -31,15 +32,21 @@ static void qemu_x86_fwcfg_read_entry_pio(uint16_t entry, /* * writting FW_CFG_INVALID will cause read operation to resume at * last offset, otherwise read will start at offset 0 + * + * Note: on platform where the control register is IO port, the + * endianness is little endian. */ if (entry != FW_CFG_INVALID) - outw(entry, FW_CONTROL_PORT); + outw(cpu_to_le16(entry), FW_CONTROL_PORT); + + /* the endianness of data register is string-preserving */ while (size--) data[i++] = inb(FW_DATA_PORT); } static void qemu_x86_fwcfg_read_entry_dma(struct fw_cfg_dma_access *dma) { + /* the DMA address register is big endian */ outl(cpu_to_be32((uint32_t)dma), FW_DMA_PORT_HIGH); while (be32_to_cpu(dma->control) & ~FW_CFG_DMA_ERROR) |
