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Commit e143364b authored by Noralf Trønnes's avatar Noralf Trønnes
Browse files

drm/tinydrm: Remove tinydrm_spi_max_transfer_size() 



spi-bcm2835 can handle >64kB buffers now so there is no need to check
->max_dma_len. The tinydrm_spi_max_transfer_size() max_len argument is
not used by any callers, so not needed.

Then we have the spi_max module parameter. It was added because
staging/fbtft has support for it and there was a report that someone used
it to set a small buffer size to avoid popping on a USB soundcard on a
Raspberry Pi. In hindsight it shouldn't have been added, I should have
waited for it to become a problem first. I don't know it anyone is
actually using it, but since tinydrm_spi_transfer() is being moved to
mipi-dbi, I'm taking the opportunity to remove it. I'll add it back to
mipi-dbi if someone complains.

With that out of the way, spi_max_transfer_size() can be used instead.

The chosen 16kB buffer size for Type C Option 1 (9-bit) interface is
somewhat arbitrary, but a bigger buffer will have a miniscule impact on
transfer speed, so it's probably fine.

Acked-by: default avatarSam Ravnborg <sam@ravnborg.org>
Signed-off-by: default avatarNoralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190719155916.62465-6-noralf@tronnes.org
parent 8a18ac3a

drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c

+1 −36
Original line number Diff line number Diff line
@@ -18,41 +18,8 @@ 
#include <drm/drm_rect.h>

#include <drm/tinydrm/tinydrm-helpers.h>



static unsigned int spi_max;

module_param(spi_max, uint, 0400);

MODULE_PARM_DESC(spi_max, "Set a lower SPI max transfer size");



#if IS_ENABLED(CONFIG_SPI)



/**

 * tinydrm_spi_max_transfer_size - Determine max SPI transfer size

 * @spi: SPI device

 * @max_len: Maximum buffer size needed (optional)

 *

 * This function returns the maximum size to use for SPI transfers. It checks

 * the SPI master, the optional @max_len and the module parameter spi_max and

 * returns the smallest.

 *

 * Returns:

 * Maximum size for SPI transfers

 */

size_t tinydrm_spi_max_transfer_size(struct spi_device *spi, size_t max_len)

{

	size_t ret;



	ret = min(spi_max_transfer_size(spi), spi->master->max_dma_len);

	if (max_len)

		ret = min(ret, max_len);

	if (spi_max)

		ret = min_t(size_t, ret, spi_max);

	ret &= ~0x3;

	if (ret < 4)

		ret = 4;



	return ret;

}

EXPORT_SYMBOL(tinydrm_spi_max_transfer_size);



/**

 * tinydrm_spi_transfer - SPI transfer helper

 * @spi: SPI device
@@ -75,21 +42,19 @@ int tinydrm_spi_transfer(struct spi_device *spi, u32 speed_hz, 
			 struct spi_transfer *header, 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;

	u16 *swap_buf = NULL;

	size_t max_chunk;

	size_t chunk;

	int ret = 0;



	if (WARN_ON_ONCE(bpw != 8 && bpw != 16))

		return -EINVAL;



	max_chunk = tinydrm_spi_max_transfer_size(spi, 0);



	if (bpw == 16 && !spi_is_bpw_supported(spi, 16)) {

		tr.bits_per_word = 8;

		if (tinydrm_machine_little_endian()) {

drivers/gpu/drm/tinydrm/mipi-dbi.c

+2 −8
Original line number Diff line number Diff line
@@ -964,15 +964,9 @@ static int mipi_dbi_typec3_command(struct mipi_dbi *mipi, u8 *cmd, 
int mipi_dbi_spi_init(struct spi_device *spi, struct mipi_dbi *mipi,

		      struct gpio_desc *dc)

{

	size_t tx_size = tinydrm_spi_max_transfer_size(spi, 0);

	struct device *dev = &spi->dev;

	int ret;



	if (tx_size < 16) {

		DRM_ERROR("SPI transmit buffer too small: %zu\n", tx_size);

		return -EINVAL;

	}



	/*

	 * Even though it's not the SPI device that does DMA (the master does),

	 * the dma mask is necessary for the dma_alloc_wc() in
@@ -1001,8 +995,8 @@ int mipi_dbi_spi_init(struct spi_device *spi, struct mipi_dbi *mipi, 
			mipi->swap_bytes = true;

	} else {

		mipi->command = mipi_dbi_typec1_command;

		mipi->tx_buf9_len = tx_size;

		mipi->tx_buf9 = devm_kmalloc(dev, tx_size, GFP_KERNEL);

		mipi->tx_buf9_len = SZ_16K;

		mipi->tx_buf9 = devm_kmalloc(dev, mipi->tx_buf9_len, GFP_KERNEL);

		if (!mipi->tx_buf9)

			return -ENOMEM;

	}

include/drm/tinydrm/tinydrm-helpers.h

+0 −1
Original line number Diff line number Diff line
@@ -41,7 +41,6 @@ int tinydrm_display_pipe_init(struct drm_device *drm, 
			      const struct drm_display_mode *mode,

			      unsigned int rotation);



size_t tinydrm_spi_max_transfer_size(struct spi_device *spi, size_t max_len);

int tinydrm_spi_transfer(struct spi_device *spi, u32 speed_hz,

			 struct spi_transfer *header, u8 bpw, const void *buf,

			 size_t len);