Messages in this thread | | | Date | Mon, 30 Oct 2023 14:52:30 -0700 | Subject | Re: [PATCH v4 2/5] r8169: Coalesce RTL8411b PHY power-down recovery calls to reduce spinlock stalls | From | Jacob Keller <> |
| |
On 10/29/2023 4:04 AM, Mirsad Goran Todorovac wrote: > On RTL8411b the RX unit gets confused if the PHY is powered-down. > This was reported in [0] and confirmed by Realtek. Realtek provided > a sequence to fix the RX unit after PHY wakeup. > > A series of about 130 r8168_mac_ocp_write() calls is performed to > program the RTL registers for recovery. > > With about 130 of these sequential calls to r8168_mac_ocp_write() this looks like > a lock storm that will stall all of the cores and CPUs on the same memory controller > for certain time I/O takes to finish. > > In a sequential case of RTL register programming, a sequence of writes to the RTL > registers can be coalesced under a same raw spinlock. This can dramatically decrease > the number of bus stalls in a multicore or multi-CPU system: > > static void rtl_hw_start_8411_2(struct rtl8169_private *tp) > { > > ... > > /* The following Realtek-provided magic fixes an issue with the RX unit > * getting confused after the PHY having been powered-down. > */ > > static const struct recover_8411b_info init_zero_seq[] = { > { 0xFC28, 0x0000 }, { 0xFC2A, 0x0000 }, { 0xFC2C, 0x0000 }, > ... > }; > > static const struct recover_8411b_info recover_seq[] = { > { 0xF800, 0xE008 }, { 0xF802, 0xE00A }, { 0xF804, 0xE00C }, > ... > }; > > static const struct recover_8411b_info final_seq[] = { > { 0xFC2A, 0x0743 }, { 0xFC2C, 0x0801 }, { 0xFC2E, 0x0BE9 }, > ... > }; > > r8168_mac_ocp_write_seq(tp, init_zero_seq); > mdelay(3); > r8168_mac_ocp_write(tp, 0xFC26, 0x0000); > r8168_mac_ocp_write_seq(tp, recover_seq); > r8168_mac_ocp_write(tp, 0xFC26, 0x8000); > r8168_mac_ocp_write_seq(tp, final_seq); > } > > The hex data is preserved intact through s/r8168_mac_ocp_write[(]tp,/{ / and s/[)];/ },/ > functions that only changed the function names and the ending of the line, so the actual > hex data is unchanged. > > Note that the reason for the introduction of the original commit > was to enable recovery of the RX unit on the RTL8411b which was confused by the > powered-down PHY. This sequence of r8168_mac_ocp_write() calls amplifies the problem > into a series of about 500+ memory bus locks, most waiting for the main MMIO memory > read-modify-write under a LOCK. The memory barrier in RTL_W32 should suffice for > the programming sequence to reach RTL NIC registers. > > [0] https://bugzilla.redhat.com/show_bug.cgi?id=1692075 > > Fixes: fe4e8db0392a6 ("r8169: fix issue with confused RX unit after PHY power-down on RTL8411b") > Cc: Heiner Kallweit <hkallweit1@gmail.com> > Cc: Marco Elver <elver@google.com> > Cc: nic_swsd@realtek.com > Cc: "David S. Miller" <davem@davemloft.net> > Cc: Eric Dumazet <edumazet@google.com> > Cc: Jakub Kicinski <kuba@kernel.org> > Cc: Paolo Abeni <pabeni@redhat.com> > Cc: netdev@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Link: https://lore.kernel.org/lkml/20231028005153.2180411-1-mirsad.todorovac@alu.unizg.hr/ > Link: https://lore.kernel.org/lkml/20231028110459.2644926-1-mirsad.todorovac@alu.unizg.hr/ > Signed-off-by: Mirsad Goran Todorovac <mirsad.todorovac@alu.unizg.hr> > ---
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
| |