Re: [U-Boot] [PATCH 0/4 V2] Add basic NVIDIA Tegra2 SoC support

Dear Tom Warren,

In message AANLkTikCQ_0cNFRj_5S2zShcJ-2qyvi24yeH0DcqEPf_@mail.gmail.com you wrote:

So instead of, say uart->lcr = 0, you'd prefer writel(0, uart->lcr), where writel = __arch_putl(v, a) = (*(volatile unsigned int *)(a) = (v))?

Please see the thread "ARM: Avoid compiler optimization for usages of readb, writeb and friends."

Is that different enough from 'uart->lcr = 0' to warrant the change?

Yes, it is - in recent (i. e. fixed) code.

Does it add some HW barriers or forced read-before-write that the 'volatile' struct doesn't?

Yes, it does. See above.

Best regards,

Wolfgang Denk