083a6c23b9
Prep work before moving the function to mipi-dbi. tinydrm_spi_transfer() was made to support one class of drivers in drivers/staging/fbtft that has not been converted to DRM yet, so strip away the unused functionality: - Start byte (header) is not used. - No driver relies on the automatic 16-bit byte swapping on little endian machines with SPI controllers only supporting 8 bits per word. Other changes: - No need to initialize ret - No need for the WARN since mipi-dbi only uses 8 and 16 bpw. - Use spi_message_init_with_transfers() Cc: David Lechner <david@lechnology.com> Acked-by: : David Lechner <david@lechnology.com> Signed-off-by: Noralf Trønnes <noralf@tronnes.org> Link: https://patchwork.freedesktop.org/patch/msgid/20190719155916.62465-7-noralf@tronnes.org
71 lines
1.4 KiB
C
71 lines
1.4 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2016 Noralf Trønnes
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*/
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#include <linux/backlight.h>
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#include <linux/dma-buf.h>
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#include <linux/module.h>
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#include <linux/pm.h>
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#include <linux/spi/spi.h>
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#include <linux/swab.h>
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#include <drm/drm_device.h>
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#include <drm/drm_drv.h>
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#include <drm/drm_fourcc.h>
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#include <drm/drm_framebuffer.h>
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#include <drm/drm_print.h>
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#include <drm/drm_rect.h>
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#include <drm/tinydrm/tinydrm-helpers.h>
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#if IS_ENABLED(CONFIG_SPI)
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/**
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* tinydrm_spi_transfer - SPI transfer helper
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* @spi: SPI device
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* @speed_hz: Override speed (optional)
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* @bpw: Bits per word
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* @buf: Buffer to transfer
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* @len: Buffer length
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*
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* This SPI transfer helper breaks up the transfer of @buf into chunks which
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* the SPI controller driver can handle.
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*
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* Returns:
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* Zero on success, negative error code on failure.
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*/
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int tinydrm_spi_transfer(struct spi_device *spi, u32 speed_hz,
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u8 bpw, const void *buf, size_t len)
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{
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size_t max_chunk = spi_max_transfer_size(spi);
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struct spi_transfer tr = {
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.bits_per_word = bpw,
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.speed_hz = speed_hz,
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};
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struct spi_message m;
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size_t chunk;
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int ret;
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spi_message_init_with_transfers(&m, &tr, 1);
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while (len) {
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chunk = min(len, max_chunk);
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tr.tx_buf = buf;
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tr.len = chunk;
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buf += chunk;
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len -= chunk;
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ret = spi_sync(spi, &m);
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if (ret)
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return ret;
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}
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return 0;
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}
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EXPORT_SYMBOL(tinydrm_spi_transfer);
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#endif /* CONFIG_SPI */
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MODULE_LICENSE("GPL");
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