net: stmmac: Avoid DMA_CHAN_CONTROL write if no Split Header support
The driver assumes that split headers can be enabled/disabled without stopping/starting the device, so it writes DMA_CHAN_CONTROL from stmmac_set_features(). However, on my system (IP v5.10a without Split Header support), simply writing DMA_CHAN_CONTROL when DMA is running (for example, with the commands below) leads to a TX watchdog timeout. host$ socat TCP-LISTEN:1024,fork,reuseaddr - & device$ ethtool -K eth0 tso off device$ ethtool -K eth0 tso on device$ dd if=/dev/zero bs=1M count=10 | socat - TCP4:host:1024 <tx watchdog timeout> Note that since my IP is configured without Split Header support, the driver always just reads and writes the same value to the DMA_CHAN_CONTROL register. I don't have access to any platforms with Split Header support so I don't know if these writes to the DMA_CHAN_CONTROL while DMA is running actually work properly on such systems. I could not find anything in the databook that says that DMA_CHAN_CONTROL should not be written when the DMA is running. But on systems without Split Header support, there is in any case no need to call enable_sph() in stmmac_set_features() at all since SPH can never be toggled, so we can avoid the watchdog timeout there by skipping this call. Fixes: 8c6fc097 ("net: stmmac: gmac4+: Add Split Header support") Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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