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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: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190719155916.62465-6-noralf@tronnes.org
This commit is contained in:
Noralf Trønnes 2019-07-19 17:59:10 +02:00
parent 8a18ac3a7d
commit e143364b4c
3 changed files with 3 additions and 45 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
View File

@ -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()) {

10
drivers/gpu/drm/tinydrm/mipi-dbi.c
View File

@ -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;
}

1
include/drm/tinydrm/tinydrm-helpers.h
View File

@ -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);