From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754007AbbC3R4n (ORCPT ); Mon, 30 Mar 2015 13:56:43 -0400 Received: from p3plsmtpa07-05.prod.phx3.secureserver.net ([173.201.192.234]:58510 "EHLO p3plsmtpa07-05.prod.phx3.secureserver.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753685AbbC3R4f (ORCPT ); Mon, 30 Mar 2015 13:56:35 -0400 From: Aaron Brice To: broonie@kernel.org Cc: linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org, stefan@agner.ch Subject: [PATCH v2 2/2] spi: fsl-dspi: Add ~50ns delay between cs and sck Date: Mon, 30 Mar 2015 10:49:16 -0700 Message-Id: <1427737756-20487-3-git-send-email-aaron.brice@datasoft.com> X-Mailer: git-send-email 2.1.0 In-Reply-To: <1427737756-20487-1-git-send-email-aaron.brice@datasoft.com> References: <1427737756-20487-1-git-send-email-aaron.brice@datasoft.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add delay between chip select and clock signals, before clock starts and after clock stops. Signed-off-by: Aaron Brice --- drivers/spi/spi-fsl-dspi.c | 53 ++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 51 insertions(+), 2 deletions(-) diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c index 96cac87..41284cc 100644 --- a/drivers/spi/spi-fsl-dspi.c +++ b/drivers/spi/spi-fsl-dspi.c @@ -20,6 +20,7 @@ #include #include #include +#include #include #include #include @@ -51,7 +52,7 @@ #define SPI_CTAR_CPOL(x) ((x) << 26) #define SPI_CTAR_CPHA(x) ((x) << 25) #define SPI_CTAR_LSBFE(x) ((x) << 24) -#define SPI_CTAR_PCSSCR(x) (((x) & 0x00000003) << 22) +#define SPI_CTAR_PCSSCK(x) (((x) & 0x00000003) << 22) #define SPI_CTAR_PASC(x) (((x) & 0x00000003) << 20) #define SPI_CTAR_PDT(x) (((x) & 0x00000003) << 18) #define SPI_CTAR_PBR(x) (((x) & 0x00000003) << 16) @@ -59,6 +60,7 @@ #define SPI_CTAR_ASC(x) (((x) & 0x0000000f) << 8) #define SPI_CTAR_DT(x) (((x) & 0x0000000f) << 4) #define SPI_CTAR_BR(x) ((x) & 0x0000000f) +#define SPI_CTAR_SCALE_BITS 0xf #define SPI_CTAR0_SLAVE 0x0c @@ -99,6 +101,8 @@ #define SPI_CS_ASSERT 0x02 #define SPI_CS_DROP 0x04 +#define NSEC_PER_SEC 1000000000L + struct chip_data { u32 mcr_val; u32 ctar_val; @@ -174,6 +178,40 @@ static void hz_to_spi_baud(char *pbr, char *br, int speed_hz, } } +static void ns_delay_scale(char *psc, char *sc, int delay_ns, + unsigned long clkrate) +{ + int pscale_tbl[4] = {1, 3, 5, 7}; + int scale_needed, scale, minscale = INT_MAX; + int i, j; + u32 remainder; + + scale_needed = div_u64_rem((u64)delay_ns * clkrate, NSEC_PER_SEC, + &remainder); + if (remainder) + scale_needed++; + + for (i = 0; i < ARRAY_SIZE(pscale_tbl); i++) + for (j = 0; j <= SPI_CTAR_SCALE_BITS; j++) { + scale = pscale_tbl[i] * (2 << j); + if (scale >= scale_needed) { + if (scale < minscale) { + minscale = scale; + *psc = i; + *sc = j; + } + break; + } + } + + if (minscale == INT_MAX) { + pr_warn("Cannot find correct scale values for %dns delay at clkrate %ld, using max prescaler value", + delay_ns, clkrate); + *psc = ARRAY_SIZE(pscale_tbl) - 1; + *sc = SPI_CTAR_SCALE_BITS; + } +} + static int dspi_transfer_write(struct fsl_dspi *dspi) { int tx_count = 0; @@ -352,7 +390,8 @@ static int dspi_setup(struct spi_device *spi) { struct chip_data *chip; struct fsl_dspi *dspi = spi_master_get_devdata(spi->master); - unsigned char br = 0, pbr = 0, fmsz = 0; + unsigned char br = 0, pbr = 0, pcssck = 0, cssck = 0; + unsigned char pasc = 0, asc = 0, fmsz = 0; if ((spi->bits_per_word >= 4) && (spi->bits_per_word <= 16)) { fmsz = spi->bits_per_word - 1; @@ -377,10 +416,20 @@ static int dspi_setup(struct spi_device *spi) hz_to_spi_baud(&pbr, &br, spi->max_speed_hz, clk_get_rate(dspi->clk)); + /* Set PCS to SCK delay scale values for 50ns delay*/ + ns_delay_scale(&pcssck, &cssck, 50, clk_get_rate(dspi->clk)); + + /* Set After SCK delay scale values for 50ns delay*/ + ns_delay_scale(&pasc, &asc, 50, clk_get_rate(dspi->clk)); + chip->ctar_val = SPI_CTAR_FMSZ(fmsz) | SPI_CTAR_CPOL(spi->mode & SPI_CPOL ? 1 : 0) | SPI_CTAR_CPHA(spi->mode & SPI_CPHA ? 1 : 0) | SPI_CTAR_LSBFE(spi->mode & SPI_LSB_FIRST ? 1 : 0) + | SPI_CTAR_PCSSCK(pcssck) + | SPI_CTAR_CSSCK(cssck) + | SPI_CTAR_PASC(pasc) + | SPI_CTAR_ASC(asc) | SPI_CTAR_PBR(pbr) | SPI_CTAR_BR(br); -- 2.1.0