From fd5736bf9f235d26c83cac8a16c70bbdafa55abe Mon Sep 17 00:00:00 2001 From: Alex Marginean Date: Thu, 12 Nov 2020 20:26:08 +0200 Subject: enetc: Workaround for MDIO register access issue Due to a hardware issue, an access to MDIO registers that is concurrent with other ENETC register accesses may lead to the MDIO access being dropped or corrupted. The workaround introduces locking for all register accesses to the ENETC register space. To reduce performance impact, a readers-writers locking scheme has been implemented. The writer in this case is the MDIO access code (irrelevant whether that MDIO access is a register read or write), and the reader is any access code to non-MDIO ENETC registers. Also, the datapath functions acquire the read lock fewer times and use _hot accessors. All the rest of the code uses the _wa accessors which lock every register access. The commit introducing MDIO support is - commit ebfcb23d62ab ("enetc: Add ENETC PF level external MDIO support") but due to subsequent refactoring this patch is applicable on top of a later commit. Fixes: 6517798dd343 ("enetc: Make MDIO accessors more generic and export to include/linux/fsl") Signed-off-by: Alex Marginean Signed-off-by: Vladimir Oltean Signed-off-by: Claudiu Manoil Link: https://lore.kernel.org/r/20201112182608.26177-1-claudiu.manoil@nxp.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/freescale/enetc/enetc_hw.h | 115 ++++++++++++++++++++++-- 1 file changed, 109 insertions(+), 6 deletions(-) (limited to 'drivers/net/ethernet/freescale/enetc/enetc_hw.h') diff --git a/drivers/net/ethernet/freescale/enetc/enetc_hw.h b/drivers/net/ethernet/freescale/enetc/enetc_hw.h index 17cf7c94fdb5..eb6bbf1113c7 100644 --- a/drivers/net/ethernet/freescale/enetc/enetc_hw.h +++ b/drivers/net/ethernet/freescale/enetc/enetc_hw.h @@ -324,14 +324,100 @@ struct enetc_hw { void __iomem *global; }; -/* general register accessors */ -#define enetc_rd_reg(reg) ioread32((reg)) -#define enetc_wr_reg(reg, val) iowrite32((val), (reg)) +/* ENETC register accessors */ + +/* MDIO issue workaround (on LS1028A) - + * Due to a hardware issue, an access to MDIO registers + * that is concurrent with other ENETC register accesses + * may lead to the MDIO access being dropped or corrupted. + * To protect the MDIO accesses a readers-writers locking + * scheme is used, where the MDIO register accesses are + * protected by write locks to insure exclusivity, while + * the remaining ENETC registers are accessed under read + * locks since they only compete with MDIO accesses. + */ +extern rwlock_t enetc_mdio_lock; + +/* use this locking primitive only on the fast datapath to + * group together multiple non-MDIO register accesses to + * minimize the overhead of the lock + */ +static inline void enetc_lock_mdio(void) +{ + read_lock(&enetc_mdio_lock); +} + +static inline void enetc_unlock_mdio(void) +{ + read_unlock(&enetc_mdio_lock); +} + +/* use these accessors only on the fast datapath under + * the enetc_lock_mdio() locking primitive to minimize + * the overhead of the lock + */ +static inline u32 enetc_rd_reg_hot(void __iomem *reg) +{ + lockdep_assert_held(&enetc_mdio_lock); + + return ioread32(reg); +} + +static inline void enetc_wr_reg_hot(void __iomem *reg, u32 val) +{ + lockdep_assert_held(&enetc_mdio_lock); + + iowrite32(val, reg); +} + +/* internal helpers for the MDIO w/a */ +static inline u32 _enetc_rd_reg_wa(void __iomem *reg) +{ + u32 val; + + enetc_lock_mdio(); + val = ioread32(reg); + enetc_unlock_mdio(); + + return val; +} + +static inline void _enetc_wr_reg_wa(void __iomem *reg, u32 val) +{ + enetc_lock_mdio(); + iowrite32(val, reg); + enetc_unlock_mdio(); +} + +static inline u32 _enetc_rd_mdio_reg_wa(void __iomem *reg) +{ + unsigned long flags; + u32 val; + + write_lock_irqsave(&enetc_mdio_lock, flags); + val = ioread32(reg); + write_unlock_irqrestore(&enetc_mdio_lock, flags); + + return val; +} + +static inline void _enetc_wr_mdio_reg_wa(void __iomem *reg, u32 val) +{ + unsigned long flags; + + write_lock_irqsave(&enetc_mdio_lock, flags); + iowrite32(val, reg); + write_unlock_irqrestore(&enetc_mdio_lock, flags); +} + #ifdef ioread64 -#define enetc_rd_reg64(reg) ioread64((reg)) +static inline u64 _enetc_rd_reg64(void __iomem *reg) +{ + return ioread64(reg); +} #else /* using this to read out stats on 32b systems */ -static inline u64 enetc_rd_reg64(void __iomem *reg) +static inline u64 _enetc_rd_reg64(void __iomem *reg) { u32 low, high, tmp; @@ -345,12 +431,29 @@ static inline u64 enetc_rd_reg64(void __iomem *reg) } #endif +static inline u64 _enetc_rd_reg64_wa(void __iomem *reg) +{ + u64 val; + + enetc_lock_mdio(); + val = _enetc_rd_reg64(reg); + enetc_unlock_mdio(); + + return val; +} + +/* general register accessors */ +#define enetc_rd_reg(reg) _enetc_rd_reg_wa((reg)) +#define enetc_wr_reg(reg, val) _enetc_wr_reg_wa((reg), (val)) #define enetc_rd(hw, off) enetc_rd_reg((hw)->reg + (off)) #define enetc_wr(hw, off, val) enetc_wr_reg((hw)->reg + (off), val) -#define enetc_rd64(hw, off) enetc_rd_reg64((hw)->reg + (off)) +#define enetc_rd64(hw, off) _enetc_rd_reg64_wa((hw)->reg + (off)) /* port register accessors - PF only */ #define enetc_port_rd(hw, off) enetc_rd_reg((hw)->port + (off)) #define enetc_port_wr(hw, off, val) enetc_wr_reg((hw)->port + (off), val) +#define enetc_port_rd_mdio(hw, off) _enetc_rd_mdio_reg_wa((hw)->port + (off)) +#define enetc_port_wr_mdio(hw, off, val) _enetc_wr_mdio_reg_wa(\ + (hw)->port + (off), val) /* global register accessors - PF only */ #define enetc_global_rd(hw, off) enetc_rd_reg((hw)->global + (off)) #define enetc_global_wr(hw, off, val) enetc_wr_reg((hw)->global + (off), val) -- cgit