drm/tinydrm: Move tinydrm_spi_transfer()

This is only used by mipi-dbi drivers so move it there.

The reason this isn't moved to the SPI subsystem is that it will in a
later patch pass a dummy rx buffer for SPI controllers that need this.
Low memory boards (64MB) can run into a problem allocating such a "large"
contiguous buffer on every transfer after a long up time.
This leaves a very specific use case, so we'll keep the function here.
mipi-dbi will first go through a refactoring though, before this will
be done.

Remove SPI todo entry now that we're done with the tinydrm.ko SPI code.

v2: Drop moving the mipi_dbi_spi_init() declaration (Sam)

Cc: David Lechner <david@lechnology.com>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: : David Lechner <david@lechnology.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190719155916.62465-8-noralf@tronnes.org

1 files changed, 47 insertions, 2 deletions

diff --git a/drivers/gpu/drm/tinydrm/mipi-dbi.c b/drivers/gpu/drm/tinydrm/mipi-dbi.c
index 8fb6ce4ca6fc..6a8f2d66377f 100644
--- a/drivers/gpu/drm/tinydrm/mipi-dbi.c
+++ b/drivers/gpu/drm/tinydrm/mipi-dbi.c
@@ -926,7 +926,7 @@ static int mipi_dbi_typec3_command(struct mipi_dbi *mipi, u8 *cmd,
 
 	gpiod_set_value_cansleep(mipi->dc, 0);
 	speed_hz = mipi_dbi_spi_cmd_max_speed(spi, 1);
-	ret = tinydrm_spi_transfer(spi, speed_hz, 8, cmd, 1);
+	ret = mipi_dbi_spi_transfer(spi, speed_hz, 8, cmd, 1);
 	if (ret || !num)
 		return ret;
 
@@ -936,7 +936,7 @@ static int mipi_dbi_typec3_command(struct mipi_dbi *mipi, u8 *cmd,
 	gpiod_set_value_cansleep(mipi->dc, 1);
 	speed_hz = mipi_dbi_spi_cmd_max_speed(spi, num);
 
-	return tinydrm_spi_transfer(spi, speed_hz, bpw, par, num);
+	return mipi_dbi_spi_transfer(spi, speed_hz, bpw, par, num);
 }
 
 /**
@@ -1007,6 +1007,51 @@ int mipi_dbi_spi_init(struct spi_device *spi, struct mipi_dbi *mipi,
 }
 EXPORT_SYMBOL(mipi_dbi_spi_init);
 
+/**
+ * mipi_dbi_spi_transfer - SPI transfer helper
+ * @spi: SPI device
+ * @speed_hz: Override speed (optional)
+ * @bpw: Bits per word
+ * @buf: Buffer to transfer
+ * @len: Buffer length
+ *
+ * This SPI transfer helper breaks up the transfer of @buf into chunks which
+ * the SPI controller driver can handle.
+ *
+ * Returns:
+ * Zero on success, negative error code on failure.
+ */
+int mipi_dbi_spi_transfer(struct spi_device *spi, u32 speed_hz,
+			  u8 bpw, const void *buf, size_t len)
+{
+	size_t max_chunk = spi_max_transfer_size(spi);
+	struct spi_transfer tr = {
+		.bits_per_word = bpw,
+		.speed_hz = speed_hz,
+	};
+	struct spi_message m;
+	size_t chunk;
+	int ret;
+
+	spi_message_init_with_transfers(&m, &tr, 1);
+
+	while (len) {
+		chunk = min(len, max_chunk);
+
+		tr.tx_buf = buf;
+		tr.len = chunk;
+		buf += chunk;
+		len -= chunk;
+
+		ret = spi_sync(spi, &m);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(mipi_dbi_spi_transfer);
+
 #endif /* CONFIG_SPI */
 
 #ifdef CONFIG_DEBUG_FS