On 26/08/2014 at 16:17:57 +0200, Tomasz Figa wrote :

Firmware on certain boards (e.g. ODROID-U3) can leave incorrect L2C prefetch
settings configured in registers leading to crashes if L2C is enabled
without overriding them. This patch introduces bindings to enable
prefetch settings to be specified from DT and necessary support in the
driver.

Signed-off-by: Tomasz Figa <redacted>

Tested-by: Alexandre Belloni <redacted>

It is working and useful on Atmel's sama5d4 were the bootloader is not
configuring the L2C prefetch. However, I'm wondering whether we should
add support for setting L310_PREFETCH_CTRL_DATA_PREFETCH and
L310_PREFETCH_CTRL_INSTR_PREFETCH. I'm currently doing it by using
".l2c_aux_val    = L310_AUX_CTRL_DATA_PREFETCH |
L310_AUX_CTRL_INSTR_PREFETCH" (those are the same bits) but this has the
disadvantage of displaying the "L2C: platform modifies aux control
register:" twice.

+	if (!of_property_read_u32(np, "arm,prefetch-offset", &val)) {
+		prefetch &= ~L310_PREFETCH_CTRL_OFFSET_MASK;
+		prefetch |= val & L310_PREFETCH_CTRL_OFFSET_MASK;
+	}
+

While you use val directly here, later, while printing the offset, val +
1 is used. Maybe it would be better to have the same number in both
places, else you end up with having "arm,prefetch-offset = <1>" in your
DT and the kernel printing "L2C-310 ID prefetch enabled, offset 2
lines".



-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com