Re: [PATCH 5/7] drm: adv7511: Add has_dsi feature bit to struct adv7511_chip_info

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Tue, Aug 29, 2023 at 03:42:40PM +0000, Biju Das wrote:
> Hi Laurent Pinchart,
> 
> Thanks for the feedback.
> 
> > Subject: Re: [PATCH 5/7] drm: adv7511: Add has_dsi feature bit to struct
> > adv7511_chip_info
> > 
> > Hi Biju,
> > 
> > On Tue, Aug 29, 2023 at 02:19:02PM +0000, Biju Das wrote:
> > > Subject: Re: [PATCH 5/7] drm: adv7511: Add has_dsi feature bit to
> > > struct adv7511_chip_info
> > > > On Sun, Aug 13, 2023 at 07:05:10PM +0100, Biju Das wrote:
> > > > > The ADV7533 and ADV7535 have DSI support. Add a feature bit
> > > > > has_dsi to struct adv7511_chip_info for handling configuration
> > related to DSI.
> > > > >
> > > > > Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
> > > > > ---
> > > > >  drivers/gpu/drm/bridge/adv7511/adv7511.h     |  1 +
> > > > >  drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 20
> > > > > +++++++++++---------
> > > > >  2 files changed, 12 insertions(+), 9 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511.h
> > > > > b/drivers/gpu/drm/bridge/adv7511/adv7511.h
> > > > > index b29d11cae932..2a017bb31a14 100644
> > > > > --- a/drivers/gpu/drm/bridge/adv7511/adv7511.h
> > > > > +++ b/drivers/gpu/drm/bridge/adv7511/adv7511.h
> > > > > @@ -339,6 +339,7 @@ struct adv7511_chip_info {
> > > > >  	unsigned long max_lane_freq;
> > > > >  	const char * const *supply_names;
> > > > >  	unsigned int num_supplies;
> > > > > +	unsigned has_dsi:1;
> > > >
> > > > As you're not short of space here, I'd make this a bool.
> > >
> > > OK, will use bool here.
> > >
> > > > >  };
> > > > >
> > > > >  struct adv7511 {
> > > > > diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > > b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > > index f6f15c1b0882..66b3f8fcf67d 100644
> > > > > --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > > +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > > @@ -373,7 +373,7 @@ static void adv7511_power_on(struct adv7511
> > *adv7511)
> > > > >  	 */
> > > > >  	regcache_sync(adv7511->regmap);
> > > > >
> > > > > -	if (adv7511->info->type == ADV7533 || adv7511->info->type ==
> > ADV7535)
> > > > > +	if (adv7511->info->has_dsi)
> > > > >  		adv7533_dsi_power_on(adv7511);
> > > > >  	adv7511->powered = true;
> > > > >  }
> > > > > @@ -397,7 +397,7 @@ static void __adv7511_power_off(struct adv7511
> > > > > *adv7511)  static void adv7511_power_off(struct adv7511 *adv7511)  {
> > > > >  	__adv7511_power_off(adv7511);
> > > > > -	if (adv7511->info->type == ADV7533 || adv7511->info->type ==
> > ADV7535)
> > > > > +	if (adv7511->info->has_dsi)
> > > > >  		adv7533_dsi_power_off(adv7511);
> > > > >  	adv7511->powered = false;
> > > > >  }
> > > > > @@ -786,7 +786,7 @@ static void adv7511_mode_set(struct adv7511
> > *adv7511,
> > > > >  	else
> > > > >  		low_refresh_rate = ADV7511_LOW_REFRESH_RATE_NONE;
> > > > >
> > > > > -	if (adv7511->info->type == ADV7511)
> > > > > +	if (!adv7511->info->has_dsi)
> > > >
> > > > While this is functionally equivalent, is the register below really
> > > > related to DSI ? If not, I'd rather not check the has_dsi field here
> > > > but keep checking the type.
> > >
> > > What creating a packed value for this hardware difference as driver
> > > data?
> > >
> > >  { 0xfb, 0x6, 0x1} and { 0x4a, 0xc, 2) packed as unsigned int driver
> > > data low_refresh_data and we can get rid of this if statement and
> > > depack it here.
> > 
> > As we're not in a hot path, I think the most important criteria to consider
> > are maintainability and readability. Making it easy to add support for a
> > new chip without creating a mess of spaghetti code falls into those
> > criteria, but as far as I'm aware there's no indication that we will
> > suddenly see several new compatible devices.
> > 
> > When it comes to readability, code such as
> > 
> > 	if (has_dsi)
> > 		init_dsi();
> > 
> > is great, but code such as
> > 
> > 	if (has_dsi)
> > 		init_cec();
> > 
> > because only the DSI-enabled version happens to also support CEC is not
> > good. Similarly, I don't think packing the refresh rate register addresses
> > and value in the info structure would increase readability, or help in any
> > real way. I'm tempted to leave it as-is.
> 
> Agreed. Will keep as it is for low_refresh_rate() change.
> 
> > 
> > What would help readability, if you feel inclined to keep working on this
> > driver, is to replace the register addresses with named macros :-)
> > 
> > > > >  		regmap_update_bits(adv7511->regmap, 0xfb,
> > > > >  				   0x6, low_refresh_rate << 1);
> > > > >  	else
> > > > > @@ -921,7 +921,7 @@ static enum drm_mode_status
> > > > > adv7511_bridge_mode_valid(struct drm_bridge *bridge,  {
> > > > >  	struct adv7511 *adv = bridge_to_adv7511(bridge);
> > > > >
> > > > > -	if (adv->info->type == ADV7533 || adv->info->type == ADV7535)
> > > > > +	if (adv->info->has_dsi)
> > > > >  		return adv7533_mode_valid(adv, mode);
> > > > >  	else
> > > > >  		return adv7511_mode_valid(adv, mode); @@ -1086,7 +1086,7
> > @@
> > > > > static int adv7511_init_cec_regmap(struct adv7511 *adv)
> > > > >  		goto err;
> > > > >  	}
> > > > >
> > > > > -	if (adv->info->type == ADV7533 || adv->info->type == ADV7535)
> > {
> > > > > +	if (adv->info->has_dsi) {
> > > >
> > > > Same comment here, this doesn't seem logically right.
> > >
> > > But this patching is applicable for DSI.
> > 
> > CEC is an HDMI feature. The ADV7511 may not have CEC support, but it's not
> > linked to DSI as such.
> 
> OK, what about using "has_cec" here instead, which avoids 2 run time comparisons against 1??

I'm OK with that.

> > > > >  		ret = adv7533_patch_cec_registers(adv);
> > > > >  		if (ret)
> > > > >  			goto err;
> > > > > @@ -1245,7 +1245,7 @@ static int adv7511_probe(struct i2c_client
> > *i2c)
> > > > >  		goto uninit_regulators;
> > > > >  	dev_dbg(dev, "Rev. %d\n", val);
> > > > >
> > > > > -	if (info->type == ADV7511)
> > > > > +	if (!info->has_dsi)
> > > >
> > > > And here too.
> > >
> > > Will create another bool. info->has_dpi, is it ok??
> > 
> > Can't we leave type comparisons in the handful of cases where they are
> > simpler ? Is there a specific reason why you think the type enum really has
> > to go ?
> 
> Agreed, will use type here as well.
> 
> > > > >  		ret = regmap_register_patch(adv7511->regmap,
> > > > >  					    adv7511_fixed_registers,
> > > > >
> > ARRAY_SIZE(adv7511_fixed_registers));
> > > > > @@ -1316,7 +1316,7 @@ static int adv7511_probe(struct i2c_client
> > > > > *i2c)
> > > > >
> > > > >  	adv7511_audio_init(dev, adv7511);
> > > > >
> > > > > -	if (info->type == ADV7533 || info->type == ADV7535) {
> > > > > +	if (info->has_dsi) {
> > > > >  		ret = adv7533_attach_dsi(adv7511);
> > > > >  		if (ret)
> > > > >  			goto err_unregister_audio;
> > > > > @@ -1370,7 +1370,8 @@ static const struct adv7511_chip_info
> > > > adv7533_chip_info = {
> > > > >  	.max_mode_clock = 80000,
> > > > >  	.max_lane_freq = 800000,
> > > > >  	.supply_names = adv7533_supply_names,
> > > > > -	.num_supplies = ARRAY_SIZE(adv7533_supply_names)
> > > > > +	.num_supplies = ARRAY_SIZE(adv7533_supply_names),
> > > > > +	.has_dsi = 1
> > > > >  };
> > > > >
> > > > >  static const struct adv7511_chip_info adv7535_chip_info = { @@
> > > > > -1378,7 +1379,8 @@ static const struct adv7511_chip_info
> > > > adv7535_chip_info = {
> > > > >  	.max_mode_clock = 148500,
> > > > >  	.max_lane_freq = 891000,
> > > > >  	.supply_names = adv7533_supply_names,
> > > > > -	.num_supplies = ARRAY_SIZE(adv7533_supply_names)
> > > > > +	.num_supplies = ARRAY_SIZE(adv7533_supply_names),
> > > > > +	.has_dsi = 1
> > > > >  };
> > > > >
> > > > >  static const struct i2c_device_id adv7511_i2c_ids[] = {

-- 
Regards,

Laurent Pinchart