Re: [PATCH v14 05/10] drm/mediatek: Add MT8195 Embedded DisplayPort driver

CK Hu
2022-07-26T08:37:32Z

On Tue, 2022-07-26 at 11:30 +0800, Rex-BC Chen wrote:
> On Mon, 2022-07-25 at 17:23 +0800, CK Hu wrote:
> > Hi, Bo-Chen:
> >
> > On Tue, 2022-07-12 at 19:12 +0800, Bo-Chen Chen wrote:
> > > From: Markus Schneider-Pargmann <msp@baylibre.com>
> > >
> > > This patch adds a embedded displayport driver for the MediaTek
> > > mt8195
> > > SoC.
> > >
> > > It supports the MT8195, the embedded DisplayPort units. It offers
> > > DisplayPort 1.4 with up to 4 lanes.
> > >
> > > The driver creates a child device for the phy. The child device
> > > will
> > > never exist without the parent being active. As they are sharing
> > > a
> > > register range, the parent passes a regmap pointer to the child
> > > so
> > > that
> > > both can work with the same register range. The phy driver sets
> > > device
> > > data that is read by the parent to get the phy device that can be
> > > used
> > > to control the phy properties.
> > >
> > > This driver is based on an initial version by
> > > Jitao shi <jitao.shi@mediatek.com>
> > >
> > > Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> > > Signed-off-by: Guillaume Ranquet <granquet@baylibre.com>
> > > Signed-off-by: Bo-Chen Chen <rex-bc.chen@mediatek.com>
> > > ---
> >
> > [snip]
> >
> > > +
> > > +/*
> > > + * We need to handle HPD signal in eDP even though eDP is a
> > > always
> > > connected
> > > + * device. Besides connected status, there is another feature
> > > for
> > > HPD signal -
> > > + * HPD pulse: it presents an IRQ from sink devices to source
> > > devices
> > > (Refer to
> > > + * 5.1.4 of DP1.4 spec).
> > > + */
> > > +static irqreturn_t mtk_dp_hpd_isr_handler(struct mtk_dp *mtk_dp)
> > > +{
> > > + bool hpd_change = false;
> > > + u32 irq_status = mtk_dp_swirq_get_clear(mtk_dp) |
> > > + mtk_dp_hwirq_get_clear(mtk_dp);
> > > + struct mtk_dp_train_info *train_info = &mtk_dp->train_info;
> > > +
> > > + if (!irq_status)
> > > + return IRQ_HANDLED;
> > > +
> > > + if (irq_status & MTK_DP_HPD_INTERRUPT)
> > > + train_info->irq_sta.hpd_inerrupt = true;
> > > + if (irq_status & MTK_DP_HPD_CONNECT ||
> > > + irq_status & MTK_DP_HPD_DISCONNECT)
> > > + hpd_change = true;
> > > +
> > > + if (!(hpd_change))
> > > + return IRQ_WAKE_THREAD;
> > > +
> > > + if (mtk_dp_plug_state(mtk_dp))
> >
> > mtk_dp_plug_state() is called only here, and prevent function call
> > in
> > isr handler, so squash mtk_dp_plug_state() into this function.
> >
>
> Hello CK,
>
> Thanks for review.
>
> I would like to keep this because we will use this function for
> mtk_dp_plug_state_avoid_pulse() in dp patch.

Use train_info->cable_plugged_in instead of calling mtk_dp_plug_state()
because I think train_info->cable_plugged_in is synced with
mtk_dp_plug_state().

>
> > > + train_info->cable_plugged_in = true;
> > > + else
> > > + train_info->cable_plugged_in = false;
> > > +
> > > + train_info->cable_state_change = true;
> > > +
> > > + return IRQ_WAKE_THREAD;
> > > +}
> > > +
> > > +static irqreturn_t mtk_dp_hpd_event(int hpd, void *dev)
> > > +{
> > > + struct mtk_dp *mtk_dp = dev;
> > > + u32 irq_status;
> > > +
> > > + irq_status = mtk_dp_read(mtk_dp, MTK_DP_TOP_IRQ_STATUS);
> > > +
> > > + if (!irq_status)
> > > + return IRQ_HANDLED;
> > > +
> > > + if (irq_status & RGS_IRQ_STATUS_TRANSMITTER)
> > > + return mtk_dp_hpd_isr_handler(mtk_dp);
> >
> > Prevent function call in isr handler, squash
> > mtk_dp_hpd_isr_handler()
> > into this function.
> >
>
> Is this really necessary? We also modify this function in following
> patches. I think it's not a good idea to expand this.

mtk_dp_hpd_isr_handler() is only called in this function, is it really
necessary to separate this to a independent function? The function call
would increase jump instruction and stack push/pop instruction. I think
we should not do many things in isr handler. I've reviewed the later
patch and the later patch should be modified according to this.

Regards,
CK

>
> BRs,
> Bo-Chen
>
> > Regards,
> > CK
> >
> > > +
> > > + return IRQ_HANDLED;
> > > +}
> > > +
> >
> >
>
>