[PATCH v3 2/3] arm_mpam: resctrl: Add pass-through resctrl_arch_preconvert_bw()

[Ben Horgan]

resctrl rounds up the percentage value of the MBA based on the bw_gran. As
MPAM uses a binary fixed point fraction format for MBA rather than a
decimal percentage, this introduces rounding errors.

Without this additional rounding, if the user reads the value in an MB
schema and then writes it back to the schema, the value in hardware won't
change. However, with this additional rounding, this guarantee is broken
for systems with mbw_wd < 7.

resctrl is introducing resctrl_arch_preconvert_bw() to allow the arch code
to specify the conversion resctrl does to the user-provided bandwidth
value. Add the MPAM version of resctrl_arch_preconvert_bw(). This does no
conversion.

Signed-off-by: Ben Horgan <ben.horgan at arm.com>
---
 drivers/resctrl/mpam_resctrl.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/resctrl/mpam_resctrl.c b/drivers/resctrl/mpam_resctrl.c
index 226ff6f532fa..5a2104af22cc 100644
--- a/drivers/resctrl/mpam_resctrl.c
+++ b/drivers/resctrl/mpam_resctrl.c
@@ -167,6 +167,11 @@ bool resctrl_arch_get_cdp_enabled(enum resctrl_res_level rid)
 	return mpam_resctrl_controls[rid].cdp_enabled;
 }
 
+u32 resctrl_arch_preconvert_bw(u32 val, const struct rdt_resource *r)
+{
+	return val;
+}
+
 /**
  * resctrl_reset_task_closids() - Reset the PARTID/PMG values for all tasks.
  *
-- 
2.43.0