[PATCH v2 2/2] drm/tinydrm: Remove chunk splitting in tinydrm_spi_transfer

[Noralf Trønnes]

Den 10.03.2018 16.52, skrev Meghana Madhyastha:
> Remove chunk splitting in tinydrm_spi_transfer in tinydrm-helpers as the spi core will split
> a buffer into max_dma_len chunks for the spi controller driver to handle, automatic byte
> swapping in tinydrm_spi_transfer as it doesn't have users.
>
> Signed-off-by: Meghana Madhyastha <meghana.madhyastha at gmail.com>
> ---
>   drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c | 48 ++++----------------------
>   drivers/gpu/drm/tinydrm/mipi-dbi.c             | 10 ++----
>   drivers/spi/spi-bcm2835.c                      |  2 +-
>   3 files changed, 9 insertions(+), 51 deletions(-)
>
> diff --git a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> index bf96072d1b97..6064099e8e63 100644
> --- a/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> +++ b/drivers/gpu/drm/tinydrm/core/tinydrm-helpers.c
> @@ -452,62 +452,26 @@ int tinydrm_spi_transfer(struct spi_device *spi, u32 speed_hz,
>   	struct spi_transfer tr = {
>   		.bits_per_word = bpw,
>   		.speed_hz = speed_hz,
> +		.tx_buf = buf,
> +		.len = len
>   	};
>   	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);
> +	max_chunk = SIZE_MAX;

max_chunk isn't used so can be removed.
tinydrm_spi_max_transfer_size() can also be remove now.

>   
>   	if (drm_debug & DRM_UT_DRIVER)
>   		pr_debug("[drm:%s] bpw=%u, max_chunk=%zu, transfers:\n",
> -			 __func__, bpw, max_chunk);
> -
> -	if (bpw == 16 && !tinydrm_spi_bpw_supported(spi, 16)) {
> -		tr.bits_per_word = 8;
> -		if (tinydrm_machine_little_endian()) {
> -			swap_buf = kmalloc(min(len, max_chunk), GFP_KERNEL);
> -			if (!swap_buf)
> -				return -ENOMEM;
> -		}
> -	}
> +			__func__, bpw, max_chunk);
>   
>   	spi_message_init(&m);
>   	if (header)
>   		spi_message_add_tail(header, &m);
>   	spi_message_add_tail(&tr, &m);
>   
> -	while (len) {
> -		chunk = min(len, max_chunk);
> -
> -		tr.tx_buf = buf;
> -		tr.len = chunk;
> -
> -		if (swap_buf) {
> -			const u16 *buf16 = buf;
> -			unsigned int i;
> -
> -			for (i = 0; i < chunk / 2; i++)
> -				swap_buf[i] = swab16(buf16[i]);
> -
> -			tr.tx_buf = swap_buf;
> -		}
> -
> -		buf += chunk;
> -		len -= chunk;
> -
> -		tinydrm_dbg_spi_message(spi, &m);
> -		ret = spi_sync(spi, &m);
> -		if (ret)
> -			return ret;
> -	}
> +	tinydrm_dbg_spi_message(spi, &m);
>   
> -	return 0;
> +	return spi_sync(spi, &m);
>   }
>   EXPORT_SYMBOL(tinydrm_spi_transfer);
>   
> diff --git a/drivers/gpu/drm/tinydrm/mipi-dbi.c b/drivers/gpu/drm/tinydrm/mipi-dbi.c
> index 75dd65c57e74..c8af2d65c2ad 100644
> --- a/drivers/gpu/drm/tinydrm/mipi-dbi.c
> +++ b/drivers/gpu/drm/tinydrm/mipi-dbi.c
> @@ -886,15 +886,9 @@ 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
> @@ -924,8 +918,8 @@ 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;
>   	}
> diff --git a/drivers/spi/spi-bcm2835.c b/drivers/spi/spi-bcm2835.c
> index 0dcc45f158b8..2fd650891c07 100644
> --- a/drivers/spi/spi-bcm2835.c
> +++ b/drivers/spi/spi-bcm2835.c
> @@ -448,7 +448,7 @@ static void bcm2835_dma_init(struct spi_master *master, struct device *dev)
>   
>   	/* all went well, so set can_dma */
>   	master->can_dma = bcm2835_spi_can_dma;
> -	master->max_dma_len = 65535; /* limitation by BCM2835_SPI_DLEN */
> +	master->max_dma_len = 65528; /* limitation by BCM2835_SPI_DLEN */

This change belongs in the spi-bcm2835 patch.
You need to tell us why the change is needed.

Noralf.

>   	/* need to do TX AND RX DMA, so we need dummy buffers */
>   	master->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;
>