This patch adds some comments about qfw register endianness for clarity.
Signed-off-by: Miao Yan yanmiaobest@gmail.com --- arch/x86/cpu/qemu/qemu.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/arch/x86/cpu/qemu/qemu.c b/arch/x86/cpu/qemu/qemu.c index d964283..716a0ac 100644 --- a/arch/x86/cpu/qemu/qemu.c +++ b/arch/x86/cpu/qemu/qemu.c @@ -19,6 +19,7 @@ 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 @@ -33,15 +34,21 @@ 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)