Re: [PATCH v1 6/6] drm/mediatek: Add mt8195 DisplayPort driver

[Markus Schneider-Pargmann <msp@baylibre.com>]

Hi Philipp,

On Tue, Sep 07, 2021 at 10:47:41AM +0200, Philipp Zabel wrote:
> Hi Markus,
> 
> On Mon, 2021-09-06 at 21:35 +0200, Markus Schneider-Pargmann wrote:
> > This patch adds a DisplayPort driver for the Mediatek mt8195 SoC.
> > 
> > It supports both functional units on the mt8195, the embedded
> > DisplayPort as well as the external DisplayPort units. It offers
> > hot-plug-detection, audio up to 8 channels, and DisplayPort 1.4 with up
> > to 4 lanes.
> > 
> > This driver is based on an initial version by
> > Jason-JH.Lin <jason-jh.lin@mediatek.com>.
> > 
> > Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
> > ---
> [...]
> > diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
> > new file mode 100644
> > index 000000000000..1bd07c8d2f69
> > --- /dev/null
> > +++ b/drivers/gpu/drm/mediatek/mtk_dp.c
> > @@ -0,0 +1,2881 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (c) 2019 MediaTek Inc.
> > + * Copyright (c) 2021 BayLibre
> > + */
> > +
> [...]
> > +#include <linux/component.h>
> [...]
> > +#include <linux/extcon.h>
> > +#include <linux/extcon-provider.h>
> [...]
> > +#include <linux/kthread.h>
> > +#include <linux/mfd/syscon.h>
> [...]
> > +#include <linux/of_gpio.h>
> > +#include <linux/of_graph.h>
> [...]
> > +#include <linux/phy/phy.h>
> 
> The list of included headers could be pruned a bit, from a quick look it
> seems like neither of these are actually used.

Thank you. I fixed the includes for the next version.

> 
> [...]
> > +static void mtk_dp_ssc_enable(struct mtk_dp *mtk_dp, bool enable)
> > +{
> > +	mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE, DP_PWR_STATE_BANDGAP,
> > +			   DP_PWR_STATE_MASK);
> > +	mtk_dp_update_bits(mtk_dp, DP_PHY_DIG_PLL_CTL_1,
> > +			   enable ? TPLL_SSC_EN : 0, TPLL_SSC_EN);
> > +	mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
> > +			   DP_PWR_STATE_BANDGAP_TPLL_LANE, DP_PWR_STATE_MASK);
> > +
> > +	udelay(50);
> 
> Can usleep_range() be used here? Same for the other delays.

Yes, thanks, I replaced it here and everywhere else.

> 
> [...]
> > +static void mtk_dp_hpd_sink_event(struct mtk_dp *mtk_dp)
> > +{
> [...]
> > +
> > +	if (DP_GET_SINK_COUNT(sink_count) &&
> > +	    (link_status[2] & DP_DOWNSTREAM_PORT_STATUS_CHANGED)) {
> > +		mtk_dp->train_info.check_cap_count = 0;
> > +		kfree(mtk_dp->edid);
> > +		mtk_dp->edid = NULL;
> 
> Should this be protect by a lock? This looks like it could race with the
> access in mtk_dp_edid_parse_audio_capabilities() or mtk_dp_get_edid()

Completely right, I guarded all edid accesses with a mutex now. Thanks.

> 
> [...]
> > +static int mtk_dp_train_handler(struct mtk_dp *mtk_dp)
> > +{
> > +	int ret = 0;
> > +
> > +	ret = mtk_dp_train_hpd_handle(mtk_dp);
> > +
> > +	if (!mtk_dp->train_info.cable_plugged_in)
> > +		return -ENODEV;
> > +
> > +	if (mtk_dp->train_state == MTK_DP_TRAIN_STATE_NORMAL)
> > +		return ret;
> > +
> > +	switch (mtk_dp->train_state) {
> [...]
> > +	case MTK_DP_TRAIN_STATE_TRAINING:
> > +		ret = mtk_dp_train_start(mtk_dp);
> > +		if (!ret) {
> > +			mtk_dp_video_mute(mtk_dp, true);
> > +			mtk_dp_audio_mute(mtk_dp, true);
> > +			mtk_dp->train_state = MTK_DP_TRAIN_STATE_CHECKTIMING;
> > +			mtk_dp_fec_enable(mtk_dp, mtk_dp->has_fec);
> > +		}  else if (ret != -EAGAIN)
> > +			mtk_dp->train_state = MTK_DP_TRAIN_STATE_DPIDLE;
> 
> A small whitespace issue and missing braces.

Thanks for spotting, fixed.

> 
> Consider running this through checkpatch.pl --strict once for style
> issues.

Thanks for the tip, I didn't know about --strict. I now added it to my
editor tooling. Interesting thing: It picked up the missing braces as
well as all the udelays, but not the extra space before else.

> 
> [...]
> > +static irqreturn_t mtk_dp_hpd_event(int hpd, void *dev)
> > +{
> > +	struct mtk_dp *mtk_dp = dev;
> > +	uint32_t irq_status;
> > +
> > +	irq_status = mtk_dp_read(mtk_dp, MTK_DP_TOP_IRQ_STATUS);
> > +
> > +	if (!irq_status)
> > +		return IRQ_HANDLED;
> 
> This check seems superfluous given that only the
> RGS_IRQ_STATUS_TRANSMITTER bit is checked right below:

Thanks, I removed it.

> 
> > +	if (irq_status & RGS_IRQ_STATUS_TRANSMITTER)
> > +		return mtk_dp_hpd_isr_handler(mtk_dp);
> > +
> > +	return IRQ_HANDLED;
> > +}
> [...]
> > +static struct edid *mtk_dp_get_edid(struct drm_bridge *bridge,
> > +				    struct drm_connector *connector)
> > +{
> > +	struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
> > +	bool pre_enabled = mtk_dp->pre_enabled;
> > +
> > +	if (mtk_dp->edid)
> > +		kfree(mtk_dp->edid);
> 
> Unnecessary check, kfree() accepts NULL.

Fixed.

Thank you Philipp for the review.

Best,
Markus

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