diff options
Diffstat (limited to 'drivers/gpu/drm/drm_mipi_dbi.c')
| -rw-r--r-- | drivers/gpu/drm/drm_mipi_dbi.c | 35 |
1 files changed, 19 insertions, 16 deletions
diff --git a/drivers/gpu/drm/drm_mipi_dbi.c b/drivers/gpu/drm/drm_mipi_dbi.c index daac649aabdb..fa8aba6dc81c 100644 --- a/drivers/gpu/drm/drm_mipi_dbi.c +++ b/drivers/gpu/drm/drm_mipi_dbi.c @@ -824,15 +824,6 @@ u32 mipi_dbi_spi_cmd_max_speed(struct spi_device *spi, size_t len) } EXPORT_SYMBOL(mipi_dbi_spi_cmd_max_speed); -static bool mipi_dbi_machine_little_endian(void) -{ -#if defined(__LITTLE_ENDIAN) - return true; -#else - return false; -#endif -} - /* * MIPI DBI Type C Option 1 * @@ -855,7 +846,7 @@ static int mipi_dbi_spi1e_transfer(struct mipi_dbi *dbi, int dc, const void *buf, size_t len, unsigned int bpw) { - bool swap_bytes = (bpw == 16 && mipi_dbi_machine_little_endian()); + bool swap_bytes = (bpw == 16); size_t chunk, max_chunk = dbi->tx_buf9_len; struct spi_device *spi = dbi->spi; struct spi_transfer tr = { @@ -1004,7 +995,7 @@ static int mipi_dbi_spi1_transfer(struct mipi_dbi *dbi, int dc, size_t chunk = min(len, max_chunk); unsigned int i; - if (bpw == 16 && mipi_dbi_machine_little_endian()) { + if (bpw == 16) { for (i = 0; i < (chunk * 2); i += 2) { dst16[i] = *src16 >> 8; dst16[i + 1] = *src16++ & 0xFF; @@ -1218,11 +1209,23 @@ static int mipi_dbi_typec3_command(struct mipi_dbi *dbi, u8 *cmd, * If @dc is set, a Type C Option 3 interface is assumed, if not * Type C Option 1. * - * If the SPI master driver doesn't support the necessary bits per word, - * the following transformation is used: + * If the command is %MIPI_DCS_WRITE_MEMORY_START and the pixel format is RGB565, endianness has + * to be taken into account. The MIPI DBI serial interface is big endian and framebuffers are + * assumed stored in memory as little endian (%DRM_FORMAT_BIG_ENDIAN is not supported). + * + * This is how endianness is handled: + * + * Option 1 (D/C as a bit): The buffer is sent on the wire byte by byte so the 16-bit buffer is + * byteswapped before transfer. + * + * Option 3 (D/C as a gpio): If the SPI controller supports 16 bits per word the buffer can be + * sent as-is. If not the caller is responsible for swapping the bytes + * before calling mipi_dbi_command_buf() and the buffer is sent 8 bpw. + * + * This handling is optimised for %DRM_FORMAT_RGB565 framebuffers. * - * - 9-bit: reorder buffer as 9x 8-bit words, padded with no-op command. - * - 16-bit: if big endian send as 8-bit, if little endian swap bytes + * If the interface is Option 1 and the SPI controller doesn't support 9 bits per word, + * the buffer is sent as 9x 8-bit words, padded with MIPI DCS no-op commands if necessary. * * Returns: * Zero on success, negative error code on failure. @@ -1257,7 +1260,7 @@ int mipi_dbi_spi_init(struct spi_device *spi, struct mipi_dbi *dbi, if (dc) { dbi->command = mipi_dbi_typec3_command; dbi->dc = dc; - if (mipi_dbi_machine_little_endian() && !spi_is_bpw_supported(spi, 16)) + if (!spi_is_bpw_supported(spi, 16)) dbi->swap_bytes = true; } else { dbi->command = mipi_dbi_typec1_command; |