linux-kernel - [PATCH] drm/ssd130x: Use new regmap bulk write support to drop custom bus

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Date:   Sat, 18 Jun 2022 19:43:38 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Zimmermann <tzimmermann@...e.de>,
        Mark Brown <broonie@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Marek Vasut <marex@...x.de>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH] drm/ssd130x: Use new regmap bulk write support to drop custom bus

Data writes for the ssd130x 4-wire SPI protocol need special handling, due
the Data/Command control (D/C) pin having to be toggled prior to the write.

The regmap API only allowed drivers to provide .reg_{read,write} callbacks
to do per register read/write, but didn't provide a way for drivers to do
the same for bulk read/writes.

For this reason, a custom regmap bus was used by the driver just to define
a bulk write callback that implements the D/C pin toggling. But the regmap
API has been extended to support defining bulk read/write handlers, so the
custom regmap bus is not needed anymore and could just be dropped.

Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
---

This patch depends on the following regmap fixes:

https://lkml.org/lkml/2022/6/16/198


 drivers/gpu/drm/solomon/ssd130x-spi.c | 21 +++++----------------
 1 file changed, 5 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/solomon/ssd130x-spi.c b/drivers/gpu/drm/solomon/ssd130x-spi.c
index 43722adab1f8..72f066ccd2d9 100644
--- a/drivers/gpu/drm/solomon/ssd130x-spi.c
+++ b/drivers/gpu/drm/solomon/ssd130x-spi.c
@@ -18,11 +18,6 @@ struct ssd130x_spi_transport {
 	struct gpio_desc *dc;
 };
 
-static const struct regmap_config ssd130x_spi_regmap_config = {
-	.reg_bits = 8,
-	.val_bits = 8,
-};
-
 /*
  * The regmap bus .write handler, it is just a wrapper around spi_write()
  * but toggling the Data/Command control pin (D/C#). Since for 4-wire SPI
@@ -56,17 +51,12 @@ static int ssd130x_spi_read(void *context, const void *reg, size_t reg_size,
 	return -EOPNOTSUPP;
 }
 
-/*
- * A custom bus is needed due the special write that toggles a D/C# pin,
- * another option could be to just have a .reg_write() callback but that
- * will prevent to do data writes in bulk.
- *
- * Once the regmap API is extended to support defining a bulk write handler
- * in the struct regmap_config, this can be simplified and the bus dropped.
- */
-static struct regmap_bus regmap_ssd130x_spi_bus = {
+static const struct regmap_config ssd130x_spi_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
 	.write = ssd130x_spi_write,
 	.read = ssd130x_spi_read,
+	.can_multi_write = true,
 };
 
 static int ssd130x_spi_probe(struct spi_device *spi)
@@ -90,8 +80,7 @@ static int ssd130x_spi_probe(struct spi_device *spi)
 	t->spi = spi;
 	t->dc = dc;
 
-	regmap = devm_regmap_init(dev, &regmap_ssd130x_spi_bus, t,
-				  &ssd130x_spi_regmap_config);
+	regmap = devm_regmap_init(dev, NULL, t, &ssd130x_spi_regmap_config);
 	if (IS_ERR(regmap))
 		return PTR_ERR(regmap);
 
-- 
2.36.1