From ab42676af052e6d3502b31c2dc6b07af08ff126f Mon Sep 17 00:00:00 2001 From: Thomas Petazzoni Date: Tue, 21 Feb 2017 11:28:04 +0100 Subject: net: mvpp2: handle too large value in mvpp2_rx_time_coal_set() When configuring the MVPP2_ISR_RX_THRESHOLD_REG with the RX coalescing time threshold, we do not check for the maximum allowed value supported by the driver, which means we might overflow and use a bogus value. This commit adds a check for this situation, and if a value higher than what is supported by the hardware is provided, then we use the maximum value supported by the hardware. In order to achieve this in a way that avoids overflow and rounding errors, we introduce two utility functions mvpp2_usec_to_cycles() and cycles_to_usec(). Many thanks to Russell King for suggesting this implementation. Signed-off-by: Thomas Petazzoni Acked-by: Russell King Signed-off-by: David S. Miller --- drivers/net/ethernet/marvell/mvpp2.c | 31 +++++++++++++++++++++++++++++-- 1 file changed, 29 insertions(+), 2 deletions(-) (limited to 'drivers/net/ethernet/marvell/mvpp2.c') diff --git a/drivers/net/ethernet/marvell/mvpp2.c b/drivers/net/ethernet/marvell/mvpp2.c index 679811db51a1..47fb949178b1 100644 --- a/drivers/net/ethernet/marvell/mvpp2.c +++ b/drivers/net/ethernet/marvell/mvpp2.c @@ -154,6 +154,7 @@ /* Interrupt Cause and Mask registers */ #define MVPP2_ISR_RX_THRESHOLD_REG(rxq) (0x5200 + 4 * (rxq)) +#define MVPP2_MAX_ISR_RX_THRESHOLD 0xfffff0 #define MVPP2_ISR_RXQ_GROUP_REG(rxq) (0x5400 + 4 * (rxq)) #define MVPP2_ISR_ENABLE_REG(port) (0x5420 + 4 * (port)) #define MVPP2_ISR_ENABLE_INTERRUPT(mask) ((mask) & 0xffff) @@ -4389,13 +4390,39 @@ static void mvpp2_rx_pkts_coal_set(struct mvpp2_port *port, rxq->pkts_coal); } +static u32 mvpp2_usec_to_cycles(u32 usec, unsigned long clk_hz) +{ + u64 tmp = (u64)clk_hz * usec; + + do_div(tmp, USEC_PER_SEC); + + return tmp > U32_MAX ? U32_MAX : tmp; +} + +static u32 mvpp2_cycles_to_usec(u32 cycles, unsigned long clk_hz) +{ + u64 tmp = (u64)cycles * USEC_PER_SEC; + + do_div(tmp, clk_hz); + + return tmp > U32_MAX ? U32_MAX : tmp; +} + /* Set the time delay in usec before Rx interrupt */ static void mvpp2_rx_time_coal_set(struct mvpp2_port *port, struct mvpp2_rx_queue *rxq) { - u32 val; + unsigned long freq = port->priv->tclk; + u32 val = mvpp2_usec_to_cycles(rxq->time_coal, freq); + + if (val > MVPP2_MAX_ISR_RX_THRESHOLD) { + rxq->time_coal = + mvpp2_cycles_to_usec(MVPP2_MAX_ISR_RX_THRESHOLD, freq); + + /* re-evaluate to get actual register value */ + val = mvpp2_usec_to_cycles(rxq->time_coal, freq); + } - val = (port->priv->tclk / USEC_PER_SEC) * rxq->time_coal; mvpp2_write(port->priv, MVPP2_ISR_RX_THRESHOLD_REG(rxq->id), val); } -- cgit v1.2.3-59-g8ed1b