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    Subject[PATCH net-next 2/4] net: ipa: introduce dma_addr_high32()
    Date
    Create a new helper function to encapsulate extracting the
    high-order 32 bits of a DMA address. It returns 0 for builds
    in which a DMA address is not 64 bits.

    This avoids doing a 32-position shift on a DMA address if it
    happens not to be 64 bits wide.

    Signed-off-by: Alex Elder <elder@linaro.org>
    ---
    drivers/net/ipa/gsi.c | 14 ++++++++++++--
    1 file changed, 12 insertions(+), 2 deletions(-)

    diff --git a/drivers/net/ipa/gsi.c b/drivers/net/ipa/gsi.c
    index 2119367b93ea9..53698c64cf882 100644
    --- a/drivers/net/ipa/gsi.c
    +++ b/drivers/net/ipa/gsi.c
    @@ -688,6 +688,16 @@ static void gsi_evt_ring_doorbell(struct gsi *gsi, u32 evt_ring_id, u32 index)
    iowrite32(val, gsi->virt + GSI_EV_CH_E_DOORBELL_0_OFFSET(evt_ring_id));
    }

    +/* Encapsulate extracting high-order 32 bits of DMA address */
    +static u32 dma_addr_high32(dma_addr_t addr)
    +{
    +#ifdef CONFIG_ARCH_DMA_ADDR_T_64BIT
    + return (u32)(addr >> 32);
    +#else /* !CONFIG_ARCH_DMA_ADDR_T_64BIT */
    + return 0;
    +#endif /* !CONFIG_ARCH_DMA_ADDR_T_64BIT */
    +}
    +
    /* Program an event ring for use */
    static void gsi_evt_ring_program(struct gsi *gsi, u32 evt_ring_id)
    {
    @@ -711,7 +721,7 @@ static void gsi_evt_ring_program(struct gsi *gsi, u32 evt_ring_id)
    val = evt_ring->ring.addr & GENMASK(31, 0);
    iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_2_OFFSET(evt_ring_id));

    - val = evt_ring->ring.addr >> 32;
    + val = dma_addr_high32(evt_ring->ring.addr);
    iowrite32(val, gsi->virt + GSI_EV_CH_E_CNTXT_3_OFFSET(evt_ring_id));

    /* Enable interrupt moderation by setting the moderation delay */
    @@ -819,7 +829,7 @@ static void gsi_channel_program(struct gsi_channel *channel, bool doorbell)
    val = channel->tre_ring.addr & GENMASK(31, 0);
    iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_2_OFFSET(channel_id));

    - val = channel->tre_ring.addr >> 32;
    + val = dma_addr_high32(channel->tre_ring.addr);
    iowrite32(val, gsi->virt + GSI_CH_C_CNTXT_3_OFFSET(channel_id));

    /* Command channel gets low weighted round-robin priority */
    --
    2.27.0
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