6.7-stable review patch. If anyone has any objections, please let me know.
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From: Jacob Keller jacob.e.keller@intel.com
[ Upstream commit f1f6a6b1830a8f1dc92ee26fae76333f446b0663 ]
The e1000e driver supports hardware with a variety of different clock speeds, and thus a variety of different increment values used for programming its PTP hardware clock.
The values currently programmed in e1000e_ptp_init are incorrect. In particular, only two maximum adjustments are used: 24000000 - 1, and 600000000 - 1. These were originally intended to be used with the 96 MHz clock and the 25 MHz clock.
Both of these values are actually slightly too high. For the 96 MHz clock, the actual maximum value that can safely be programmed is 23,999,938. For the 25 MHz clock, the maximum value is 599,999,904.
Worse, several devices use a 24 MHz clock or a 38.4 MHz clock. These parts are incorrectly assigned one of either the 24million or 600million values. For the 24 MHz clock, this is not a significant issue: its current increment value can support an adjustment up to 7billion in the positive direction. However, the 38.4 KHz clock uses an increment value which can only support up to 230,769,157 before it starts overflowing.
To understand where these values come from, consider that frequency adjustments have the form of:
new_incval = base_incval + (base_incval * adjustment) / (unit of adjustment)
The maximum adjustment is reported in terms of parts per billion: new_incval = base_incval + (base_incval * adjustment) / 1 billion
The largest possible adjustment is thus given by the following: max_incval = base_incval + (base_incval * max_adj) / 1 billion
Re-arranging to solve for max_adj: max_adj = (max_incval - base_incval) * 1 billion / base_incval
We also need to ensure that negative adjustments cannot underflow. This can be achieved simply by ensuring max_adj is always less than 1 billion.
Introduce new macros in e1000.h codifying the maximum adjustment in PPB for each frequency given its associated increment values. Also clarify where these values come from by commenting about the above equations.
Replace the switch statement in e1000e_ptp_init with one which mirrors the increment value switch statement from e1000e_get_base_timinica. For each device, assign the appropriate maximum adjustment based on its frequency. Some parts can have one of two frequency modes as determined by E1000_TSYNCRXCTL_SYSCFI.
Since the new flow directly matches the assignments in e1000e_get_base_timinca, and uses well defined macro names, it is much easier to verify that the resulting maximum adjustments are correct. It also avoids difficult to parse construction such as the "hw->mac.type < e1000_phc_lpt", and the use of fallthrough which was especially confusing when combined with a conditional block.
Note that I believe the current increment value configuration used for 24MHz clocks is sub-par, as it leaves at least 3 extra bits available in the INCVALUE register. However, fixing that requires more careful review of the clock rate and associated values.
Reported-by: Trey Harrison harrisondigitalmedia@gmail.com Fixes: 68fe1d5da548 ("e1000e: Add Support for 38.4MHZ frequency") Fixes: d89777bf0e42 ("e1000e: add support for IEEE-1588 PTP") Signed-off-by: Jacob Keller jacob.e.keller@intel.com Tested-by: Naama Meir naamax.meir@linux.intel.com Signed-off-by: Tony Nguyen anthony.l.nguyen@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/intel/e1000e/e1000.h | 20 ++++++++++++++++++++ drivers/net/ethernet/intel/e1000e/ptp.c | 22 +++++++++++++++------- 2 files changed, 35 insertions(+), 7 deletions(-)
diff --git a/drivers/net/ethernet/intel/e1000e/e1000.h b/drivers/net/ethernet/intel/e1000e/e1000.h index a187582d2299..ba9c19e6994c 100644 --- a/drivers/net/ethernet/intel/e1000e/e1000.h +++ b/drivers/net/ethernet/intel/e1000e/e1000.h @@ -360,23 +360,43 @@ s32 e1000e_get_base_timinca(struct e1000_adapter *adapter, u32 *timinca); * As a result, a shift of INCVALUE_SHIFT_n is used to fit a value of * INCVALUE_n into the TIMINCA register allowing 32+8+(24-INCVALUE_SHIFT_n) * bits to count nanoseconds leaving the rest for fractional nonseconds. + * + * Any given INCVALUE also has an associated maximum adjustment value. This + * maximum adjustment value is the largest increase (or decrease) which can be + * safely applied without overflowing the INCVALUE. Since INCVALUE has + * a maximum range of 24 bits, its largest value is 0xFFFFFF. + * + * To understand where the maximum value comes from, consider the following + * equation: + * + * new_incval = base_incval + (base_incval * adjustment) / 1billion + * + * To avoid overflow that means: + * max_incval = base_incval + (base_incval * max_adj) / billion + * + * Re-arranging: + * max_adj = floor(((max_incval - base_incval) * 1billion) / 1billion) */ #define INCVALUE_96MHZ 125 #define INCVALUE_SHIFT_96MHZ 17 #define INCPERIOD_SHIFT_96MHZ 2 #define INCPERIOD_96MHZ (12 >> INCPERIOD_SHIFT_96MHZ) +#define MAX_PPB_96MHZ 23999900 /* 23,999,900 ppb */
#define INCVALUE_25MHZ 40 #define INCVALUE_SHIFT_25MHZ 18 #define INCPERIOD_25MHZ 1 +#define MAX_PPB_25MHZ 599999900 /* 599,999,900 ppb */
#define INCVALUE_24MHZ 125 #define INCVALUE_SHIFT_24MHZ 14 #define INCPERIOD_24MHZ 3 +#define MAX_PPB_24MHZ 999999999 /* 999,999,999 ppb */
#define INCVALUE_38400KHZ 26 #define INCVALUE_SHIFT_38400KHZ 19 #define INCPERIOD_38400KHZ 1 +#define MAX_PPB_38400KHZ 230769100 /* 230,769,100 ppb */
/* Another drawback of scaling the incvalue by a large factor is the * 64-bit SYSTIM register overflows more quickly. This is dealt with diff --git a/drivers/net/ethernet/intel/e1000e/ptp.c b/drivers/net/ethernet/intel/e1000e/ptp.c index 02d871bc112a..bbcfd529399b 100644 --- a/drivers/net/ethernet/intel/e1000e/ptp.c +++ b/drivers/net/ethernet/intel/e1000e/ptp.c @@ -280,8 +280,17 @@ void e1000e_ptp_init(struct e1000_adapter *adapter)
switch (hw->mac.type) { case e1000_pch2lan: + adapter->ptp_clock_info.max_adj = MAX_PPB_96MHZ; + break; case e1000_pch_lpt: + if (er32(TSYNCRXCTL) & E1000_TSYNCRXCTL_SYSCFI) + adapter->ptp_clock_info.max_adj = MAX_PPB_96MHZ; + else + adapter->ptp_clock_info.max_adj = MAX_PPB_25MHZ; + break; case e1000_pch_spt: + adapter->ptp_clock_info.max_adj = MAX_PPB_24MHZ; + break; case e1000_pch_cnp: case e1000_pch_tgp: case e1000_pch_adp: @@ -289,15 +298,14 @@ void e1000e_ptp_init(struct e1000_adapter *adapter) case e1000_pch_lnp: case e1000_pch_ptp: case e1000_pch_nvp: - if ((hw->mac.type < e1000_pch_lpt) || - (er32(TSYNCRXCTL) & E1000_TSYNCRXCTL_SYSCFI)) { - adapter->ptp_clock_info.max_adj = 24000000 - 1; - break; - } - fallthrough; + if (er32(TSYNCRXCTL) & E1000_TSYNCRXCTL_SYSCFI) + adapter->ptp_clock_info.max_adj = MAX_PPB_24MHZ; + else + adapter->ptp_clock_info.max_adj = MAX_PPB_38400KHZ; + break; case e1000_82574: case e1000_82583: - adapter->ptp_clock_info.max_adj = 600000000 - 1; + adapter->ptp_clock_info.max_adj = MAX_PPB_25MHZ; break; default: break;