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    SubjectRe: [RFC Patch net-next v2 3/8] net: dsa: microchip: Initial hardware time stamping support
    On Mon, Nov 21, 2022 at 09:11:45PM +0530, Arun Ramadoss wrote:
    > +static int ksz_ptp_enable_mode(struct ksz_device *dev, bool enable)
    > +{
    > + u16 data = 0;
    > +
    > + /* Enable PTP mode */
    > + if (enable)
    > + data = PTP_ENABLE;
    > +
    > + return ksz_rmw16(dev, REG_PTP_MSG_CONF1, PTP_ENABLE, data);
    > +}
    > +
    > +static int ksz_set_hwtstamp_config(struct ksz_device *dev, int port,
    > + struct hwtstamp_config *config)
    > +{
    > + struct ksz_tagger_data *tagger_data = ksz_tagger_data(dev->ds);
    > + struct ksz_port *prt = &dev->ports[port];
    > + bool rx_on;
    > +
    > + /* reserved for future extensions */
    > + if (config->flags)
    > + return -EINVAL;
    > +
    > + switch (config->tx_type) {
    > + case HWTSTAMP_TX_OFF:
    > + case HWTSTAMP_TX_ONESTEP_P2P:
    > + prt->hwts_tx_en = config->tx_type;
    > + break;
    > + case HWTSTAMP_TX_ON:
    > + if (!is_lan937x(dev))
    > + return -ERANGE;
    > +
    > + prt->hwts_tx_en = config->tx_type;
    > + break;
    > + default:
    > + return -ERANGE;
    > + }
    > +
    > + switch (config->rx_filter) {
    > + case HWTSTAMP_FILTER_NONE:
    > + rx_on = false;
    > + break;
    > + default:
    > + rx_on = true;
    > + break;
    > + }
    > +
    > + if (rx_on != tagger_data->hwtstamp_get_state(dev->ds)) {
    > + int ret;
    > +
    > + tagger_data->hwtstamp_set_state(dev->ds, false);
    > +
    > + ret = ksz_ptp_enable_mode(dev, rx_on);
    > + if (ret)
    > + return ret;
    > +
    > + if (rx_on)
    > + tagger_data->hwtstamp_set_state(dev->ds, true);
    > + }

    What's your excuse which such a horrible code pattern? What will happen
    so bad with the packet if it's flagged with a TX timestamp request in
    KSZ_SKB_CB(skb) at the same time as REG_PTP_MSG_CONF1 is written to?

    Also, doesn't dev->ports[port].hwts_tx_en serve as a guard against
    flagging packets for TX timestamps when you shouldn't?

    > +
    > + return 0;
    > +}
    > diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
    > index 37db5156f9a3..6a909a300c13 100644
    > --- a/net/dsa/tag_ksz.c
    > +++ b/net/dsa/tag_ksz.c
    > @@ -4,6 +4,7 @@
    > * Copyright (c) 2017 Microchip Technology
    > */
    >
    > +#include <linux/dsa/ksz_common.h>
    > #include <linux/etherdevice.h>
    > #include <linux/list.h>
    > #include <net/dsa.h>
    > @@ -18,6 +19,62 @@
    > #define KSZ_EGRESS_TAG_LEN 1
    > #define KSZ_INGRESS_TAG_LEN 1
    >
    > +#define KSZ_HWTS_EN 0
    > +
    > +struct ksz_tagger_private {
    > + struct ksz_tagger_data data; /* Must be first */
    > + unsigned long state;
    > +};
    > +
    > +static struct ksz_tagger_private *
    > +ksz_tagger_private(struct dsa_switch *ds)
    > +{
    > + return ds->tagger_data;
    > +}
    > +
    > +static bool ksz_hwtstamp_get_state(struct dsa_switch *ds)
    > +{
    > + struct ksz_tagger_private *priv = ksz_tagger_private(ds);
    > +
    > + return test_bit(KSZ_HWTS_EN, &priv->state);
    > +}
    > +
    > +static void ksz_hwtstamp_set_state(struct dsa_switch *ds, bool on)
    > +{
    > + struct ksz_tagger_private *priv = ksz_tagger_private(ds);
    > +
    > + if (on)
    > + set_bit(KSZ_HWTS_EN, &priv->state);
    > + else
    > + clear_bit(KSZ_HWTS_EN, &priv->state);
    > +}

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