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Date: Fri, 20 Jul 2018 11:20:35 +0900
From: "Keiji Hayashibara" <hayashibara.keiji@...ionext.com>
To: "'Trent Piepho'" <tpiepho@...inj.com>, <robh+dt@...nel.org>,
<devicetree@...r.kernel.org>, <broonie@...nel.org>,
<mark.rutland@....com>, <linux-spi@...r.kernel.org>,
Yamada, Masahiro/山田 真弘
<yamada.masahiro@...ionext.com>,
<linux-arm-kernel@...ts.infradead.org>
Cc: <linux-kernel@...r.kernel.org>, <masami.hiramatsu@...aro.org>,
<jaswinder.singh@...aro.org>,
Hayashi, Kunihiko/林 邦彦
<hayashi.kunihiko@...ionext.com>
Subject: RE: [PATCH 2/2] spi: add SPI controller driver for UniPhier SoC
Hi Trent,
> -----Original Message-----
> From: Trent Piepho [mailto:tpiepho@...inj.com]
> Sent: Friday, July 20, 2018 4:46 AM
> Subject: Re: [PATCH 2/2] spi: add SPI controller driver for UniPhier SoC
>
> On Thu, 2018-07-19 at 15:51 +0900, Keiji Hayashibara wrote:
> >
> > +config SPI_UNIPHIER
> > + tristate "Socionext UniPhier SPI Controller"
> > + depends on (ARCH_UNIPHIER || COMPILE_TEST) && OF
> > + help
> > + This driver supports the SPI controller on Socionext
> > + UniPhier SoCs.
>
> Perhaps add the bit that this is for the SCSSI and not MCSSI here?
OK. I will add it.
> >
> > +
> > +#define BYTES_PER_WORD(x) \
> > +({ \
> > + int __x; \
> > + __x = (x <= 8) ? 1 : \
> > + (x <= 16) ? 2 : 4; \
> > + __x; \
> > +})
>
> Or:
>
> static inline bytes_per_word(unsigned int bits) {
> return bits <= 8 ? 1 : (bits <= 16 ? 2 : 4); }
I will modify.
>
> > +
> > +static inline void uniphier_spi_irq_enable(struct spi_device *spi,
> > +u32 mask) {
> > + struct uniphier_spi_priv *priv = spi_master_get_devdata(spi->master);
> > + u32 val;
> > +
> > + val = readl(priv->base + SSI_IE);
> > + val |= mask;
> > + writel(val, priv->base + SSI_IE);
> > +}
> > +
> > +static inline void uniphier_spi_irq_disable(struct spi_device *spi,
> > +u32 mask) {
> > + struct uniphier_spi_priv *priv = spi_master_get_devdata(spi->master);
> > + u32 val;
> > +
> > + val = readl(priv->base + SSI_IE);
> > + val &= ~mask;
> > + writel(val, priv->base + SSI_IE);
> > +}
> > +
> > +static void uniphier_spi_set_transfer_size(struct spi_device *spi,
> > +int size) {
> > + struct uniphier_spi_priv *priv = spi_master_get_devdata(spi->master);
> > + u32 val;
> > +
> > + val = readl(priv->base + SSI_TXWDS);
> > + val &= ~(SSI_TXWDS_WDLEN_MASK | SSI_TXWDS_DTLEN_MASK);
> > + val |= FIELD_PREP(SSI_TXWDS_WDLEN_MASK, size);
> > + val |= FIELD_PREP(SSI_TXWDS_DTLEN_MASK, size);
> > + writel(val, priv->base + SSI_TXWDS);
> > +
> > + val = readl(priv->base + SSI_RXWDS);
> > + val &= ~SSI_RXWDS_DTLEN_MASK;
> > + val |= FIELD_PREP(SSI_RXWDS_DTLEN_MASK, size);
> > + writel(val, priv->base + SSI_RXWDS); }
> > +
> > +static int uniphier_spi_set_baudrate(struct spi_device *spi, unsigned
> > +int speed) {
> > + struct uniphier_spi_priv *priv = spi_master_get_devdata(spi->master);
> > + u32 val, ckrat;
> > +
> > + /*
> > + * the supported rates are even numbers from 4 to 254. (4,6,8...254)
> > + * round up as we look for equal or less speed
> > + */
> > + ckrat = DIV_ROUND_UP(clk_get_rate(priv->clk), speed);
> > + ckrat = roundup(ckrat, 2);
> > +
> > + /* check if requested speed is too small */
> > + if (ckrat > SSI_MAX_CLK_DIVIDER)
> > + return -EINVAL;
> > +
> > + if (ckrat < SSI_MIN_CLK_DIVIDER)
> > + ckrat = SSI_MIN_CLK_DIVIDER;
> > +
> > + val = readl(priv->base + SSI_CKS);
> > + val &= ~SSI_CKS_CKRAT_MASK;
> > + val |= ckrat & SSI_CKS_CKRAT_MASK;
> > + writel(val, priv->base + SSI_CKS);
> > +
> > + return 0;
> > +}
> > +
> > +static int uniphier_spi_setup_transfer(struct spi_device *spi,
> > + struct spi_transfer *t)
> > +{
> > + struct uniphier_spi_priv *priv = spi_master_get_devdata(spi->master);
> > + u32 val;
> > + int ret;
> > +
> > + priv->error = 0;
> > + priv->tx_buf = t->tx_buf;
> > + priv->rx_buf = t->rx_buf;
> > + priv->tx_bytes = priv->rx_bytes = t->len;
> > +
> > + if (priv->bits_per_word != t->bits_per_word) {
> > + uniphier_spi_set_transfer_size(spi, t->bits_per_word);
> > + priv->bits_per_word = t->bits_per_word;
> > + }
> > +
> > + if (priv->speed_hz != t->speed_hz) {
> > + ret = uniphier_spi_set_baudrate(spi, t->speed_hz);
> > + if (ret)
> > + return ret;
> > + priv->speed_hz = t->speed_hz;
> > + }
> > +
> > + /* reset FIFOs */
> > + val = SSI_FC_TXFFL | SSI_FC_RXFFL;
> > + writel(val, priv->base + SSI_FC);
> > +
> > + return 0;
> > +}
> > +
> > +static void uniphier_spi_send(struct uniphier_spi_priv *priv) {
> > + int i, loop;
> > + u32 val = 0;
> > +
> > + loop = BYTES_PER_WORD(priv->bits_per_word);
> > + if (priv->tx_bytes < loop)
> > + loop = priv->tx_bytes;
> > +
> > + priv->tx_bytes -= loop;
> > +
> > + if (priv->tx_buf)
> > + for (i = 0; i < loop; i++) {
> > + val |= (*(const u8 *)priv->tx_buf)
> > + << (BITS_PER_BYTE * i);
>
> priv->tx_buf is already a const u8*, no need to cast it. Also in recv,
> no need to cast the pointer. It'll just hide errors if someone changes the type of the field.
I agree.
> > + (const u8 *)priv->tx_buf++;
> > + }
> > +
> > + writel(val, priv->base + SSI_TXDR);
> > +}
>
> The loop to read the data will likely be somewhat slow. It might be faster to use:
>
> val = get_unaligned_le32(priv->tx_buf);
>
> To support different sizes a switch can be used:
>
> switch (MIN(BYTES_PER_WORD(priv->bits_per_word), priv->tx_bytes)) {
> case 1:
> val = *priv->tx_buf; break;
> case 2:
> val = get_unaligned_le16(priv->tx_buf); break;
> case 4:
> val = get_unaligned_le32(priv->tx_buf); break;
> }
>
> However, I don't think either the existing code or this code is correctly handling word sizes that are not an
> even number of bytes. I think it needs to left shift the data, but of course it also depends on what the uniphier
> hardware expected in the TXDR register.
I agree. This code is simple for no loop.
I will modify to this code.
>
> > +static void uniphier_spi_recv(struct uniphier_spi_priv *priv) {
> > + int i, loop;
> > + u32 val;
> > +
> > + loop = BYTES_PER_WORD(priv->bits_per_word);
> > + if (priv->rx_bytes < loop)
> > + loop = priv->rx_bytes;
> > +
> > + priv->rx_bytes -= loop;
> > +
> > + val = readl(priv->base + SSI_RXDR);
> > +
> > + if (priv->rx_buf)
> > + for (i = 0; i < loop; i++) {
> > + val = val >> (BITS_PER_BYTE * i);
> > + *(u8 *)priv->rx_buf = val & GENMASK(7, 0);
> > + (u8 *)priv->rx_buf++;
> > + }
>
>
>
> > +}+static void uniphier_spi_fill_tx_fifo(struct uniphier_spi_priv
> > +*priv) {
> > + unsigned int tx_count;
> > + int bytes_per_word = BYTES_PER_WORD(priv->bits_per_word);
> > + u32 val;
> > +
> > + tx_count = priv->tx_bytes / bytes_per_word;
> > + if (tx_count > SSI_FIFO_DEPTH)
> > + tx_count = SSI_FIFO_DEPTH;
> > +
> > + /* set fifo threthold */
> > + val = readl(priv->base + SSI_FC);
> > + val &= ~(SSI_FC_TXFTH_MASK | SSI_FC_RXFTH_MASK);
> > + val |= FIELD_PREP(SSI_FC_TXFTH_MASK, tx_count);
> > + val |= FIELD_PREP(SSI_FC_RXFTH_MASK, tx_count);
> > + writel(val, priv->base + SSI_FC);
> > +
> > + while (tx_count--)
> > + uniphier_spi_send(priv);
> > +}
>
> If you have 24 bits per word, 3 words, that's 9 bytes.
> BYTES_PER_WORD(24) is 4. tx_count = 9/4 = 2. Looks like your tx_count rounds incorrectly, as it will only send
> 8 of the 9 bytes.
Oh, I will fix this bug.
>
> > +static int uniphier_spi_setup(struct spi_device *spi) {
>
> > +
> > + writel(val1, priv->base + SSI_CKS);
> > + writel(val2, priv->base + SSI_FPS);
> > +
> > + val1 = 0;
> > + if (spi->mode & SPI_LSB_FIRST)
> > + val1 |= FIELD_PREP(SSI_TXWDS_TDTF_MASK, 1);
> > + writel(val1, priv->base + SSI_TXWDS);
> > + writel(val1, priv->base + SSI_RXWDS);
>
> Did you see this in the spi docs?
>
> Unless each SPI slave has its own configuration registers, don't
> change them right away ... otherwise drivers could corrupt I/O
> that's in progress for other SPI devices.
>
> ** BUG ALERT: for some reason the first version of
> ** many spi_master drivers seems to get this wrong.
> ** When you code setup(), ASSUME that the controller
> ** is actively processing transfers for another device.
>
> You have one chipselect, so maybe this is ok. Until you want to support more than one chipselect.
>
> With gpio lines as chip selects, there's really no reason any spi master can't support multiple slaves.
I agree. I will re-think about this.
Thank you for your advice.
-----------------
Best Regards,
Keiji Hayashibara
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