From: Serge Semin <[email protected]> Some platforms may prohibit to access the IO-memory with instructions of certain memory widths. For instance Bailal-T1 has devices placed behind memory OCP port (which also the reason of DMA accesses being incoherent) and can't be accessed through CCA uncacheable memory with other than 4-bytes aligned (LW/SW) instructions. Ignoring this rule will cause the APB EHB error with 0xFFs returned on read operations. In order to fix the issue for this platform and for others, which may have similar problems, lets recode serial_in()/serial_out() to call a certain memory accessors in accordance with the UART registers shift setting.
Signed-off-by: Serge Semin <[email protected]> Cc: Alexey Malahov <[email protected]> Cc: Thomas Bogendoerfer <[email protected]> Cc: Paul Burton <[email protected]> Cc: Ralf Baechle <[email protected]> Cc: Arnd Bergmann <[email protected]> Cc: Rob Herring <[email protected]> Cc: [email protected] Cc: [email protected] --- arch/mips/kernel/early_printk_8250.c | 34 ++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) diff --git a/arch/mips/kernel/early_printk_8250.c b/arch/mips/kernel/early_printk_8250.c index 567c6ec0cfae..e2c2405cff62 100644 --- a/arch/mips/kernel/early_printk_8250.c +++ b/arch/mips/kernel/early_printk_8250.c @@ -23,12 +23,42 @@ void setup_8250_early_printk_port(unsigned long base, unsigned int reg_shift, static inline u8 serial_in(int offset) { - return readb(serial8250_base + (offset << serial8250_reg_shift)); + u8 ret = 0xFF; + + offset <<= serial8250_reg_shift; + switch (serial8250_reg_shift) { + case 0: + ret = readb(serial8250_base + offset); + break; + case 1: + ret = readw(serial8250_base + offset); + break; + case 2: + ret = readl(serial8250_base + offset); + break; + default: + break; + } + + return ret; } static inline void serial_out(int offset, char value) { - writeb(value, serial8250_base + (offset << serial8250_reg_shift)); + offset <<= serial8250_reg_shift; + switch (serial8250_reg_shift) { + case 0: + writeb(value, serial8250_base + offset); + break; + case 1: + writew(value, serial8250_base + offset); + break; + case 2: + writel(value, serial8250_base + offset); + break; + default: + break; + } } void prom_putchar(char c) -- 2.25.1
