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Date: Mon, 14 Jan 2019 09:38:07 +0100
From: Boris Brezillon <bbrezillon@...nel.org>
To: Schrempf Frieder <frieder.schrempf@...tron.de>
Cc: Yogesh Narayan Gaur <yogeshnarayan.gaur@....com>,
"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
"boris.brezillon@...tlin.com" <boris.brezillon@...tlin.com>,
"marek.vasut@...il.com" <marek.vasut@...il.com>,
"broonie@...nel.org" <broonie@...nel.org>,
"linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"mark.rutland@....com" <mark.rutland@....com>,
"robh@...nel.org" <robh@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"computersforpeace@...il.com" <computersforpeace@...il.com>,
"shawnguo@...nel.org" <shawnguo@...nel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v6 1/5] spi: spi-mem: Add driver for NXP FlexSPI
controller
On Thu, 10 Jan 2019 17:28:57 +0000
Schrempf Frieder <frieder.schrempf@...tron.de> wrote:
> Hi Yogesh,
>
> my comments below are mainly about things I already mentioned in my
> review for v5 and about removing or simplifying some unnecessary or
> complex code.
>
> Also as I gathered from your conversation with Boris, there's still a
> check for the length of the requested memory missing.
>
> On 08.01.19 10:24, Yogesh Narayan Gaur wrote:
> [...]
> > +
> > +static bool nxp_fspi_supports_op(struct spi_mem *mem,
> > + const struct spi_mem_op *op)
> > +{
> > + struct nxp_fspi *f = spi_controller_get_devdata(mem->spi->master);
> > + int ret;
> > +
> > + ret = nxp_fspi_check_buswidth(f, op->cmd.buswidth);
> > +
> > + if (op->addr.nbytes)
> > + ret |= nxp_fspi_check_buswidth(f, op->addr.buswidth);
> > +
> > + if (op->dummy.nbytes)
> > + ret |= nxp_fspi_check_buswidth(f, op->dummy.buswidth);
> > +
> > + if (op->data.nbytes)
> > + ret |= nxp_fspi_check_buswidth(f, op->data.buswidth);
> > +
> > + if (ret)
> > + return false;
> > +
> > + /*
> > + * The number of instructions needed for the op, needs
> > + * to fit into a single LUT entry.
> > + */
> > + if (op->addr.nbytes +
> > + (op->dummy.nbytes ? 1:0) +
> > + (op->data.nbytes ? 1:0) > 6)
> > + return false;
>
> Actually this check was only needed in the QSPI driver, as we were using
> LUT_MODE and there we needed one instruction for each address byte.
> Here the number of instructions will always fit into one LUT entry.
>
> Instead of this, a check for op->addr.nbytes > 4 (as already suggested
> in my comments for v5) would make more sense. So we can make sure that
> the address length passed in is supported (between 1 and 4 bytes).
>
> > +
> > + /* Max 64 dummy clock cycles supported */
> > + if (op->dummy.buswidth &&
> > + (op->dummy.nbytes * 8 / op->dummy.buswidth > 64))
> > + return false;
> > +
> > + /* Max data length, check controller limits and alignment */
> > + if (op->data.dir == SPI_MEM_DATA_IN &&
> > + (op->data.nbytes > f->devtype_data->ahb_buf_size ||
> > + (op->data.nbytes > f->devtype_data->rxfifo - 4 &&
> > + !IS_ALIGNED(op->data.nbytes, 8))))
> > + return false;
> > +
> > + if (op->data.dir == SPI_MEM_DATA_OUT &&
> > + op->data.nbytes > f->devtype_data->txfifo)
> > + return false;
> > +
> > + return true;
> > +}
> > +
> [...]
> > +static void nxp_fspi_select_mem(struct nxp_fspi *f, struct spi_device *spi)
> > +{
> > + unsigned long rate = spi->max_speed_hz;
> > + int ret;
> > + uint64_t size_kb;
> > +
> > + /*
> > + * Return, if previously selected slave device is same as current
> > + * requested slave device.
> > + */
> > + if (f->selected == spi->chip_select)
> > + return;
> > +
> > + /* Reset FLSHxxCR0 registers */
> > + fspi_writel(f, 0, f->iobase + FSPI_FLSHA1CR0);
> > + fspi_writel(f, 0, f->iobase + FSPI_FLSHA2CR0);
> > + fspi_writel(f, 0, f->iobase + FSPI_FLSHB1CR0);
> > + fspi_writel(f, 0, f->iobase + FSPI_FLSHB2CR0);
> > +
> > + /* Assign controller memory mapped space as size, KBytes, of flash. */
> > + size_kb = FSPI_FLSHXCR0_SZ(f->memmap_phy_size);
> > +
> > + switch (spi->chip_select) {
> > + case 0:
> > + fspi_writel(f, size_kb, f->iobase + FSPI_FLSHA1CR0);
> > + break;
> > + case 1:
> > + fspi_writel(f, size_kb, f->iobase + FSPI_FLSHA2CR0);
> > + break;
> > + case 2:
> > + fspi_writel(f, size_kb, f->iobase + FSPI_FLSHB1CR0);
> > + break;
> > + case 3:
> > + fspi_writel(f, size_kb, f->iobase + FSPI_FLSHB2CR0);
> > + break;
> > + }
>
> The switch statement above can be replaced by:
>
> fspi_writel(f, size_kb, f->iobase + FSPI_FLSHA1CR0 +
> 4 * spi->chip_select);
>
> > +
> > + dev_dbg(f->dev, "Slave device [CS:%x] selected\n", spi->chip_select);
> > +
> > + nxp_fspi_clk_disable_unprep(f);
> > +
> > + ret = clk_set_rate(f->clk, rate);
> > + if (ret)
> > + return;
> > +
> > + ret = nxp_fspi_clk_prep_enable(f);
> > + if (ret)
> > + return;
> > +
> > + f->selected = spi->chip_select;
> > +}
> > +
> > +static void nxp_fspi_read_ahb(struct nxp_fspi *f, const struct spi_mem_op *op)
> > +{
> > + u32 len = op->data.nbytes;
> > +
> > + /* Read out the data directly from the AHB buffer. */
> > + memcpy_fromio(op->data.buf.in, (f->ahb_addr + op->addr.val), len);
> > +}
> > +
> > +static void nxp_fspi_fill_txfifo(struct nxp_fspi *f,
> > + const struct spi_mem_op *op)
> > +{
> > + void __iomem *base = f->iobase;
> > + int i, j, ret;
> > + int size, tmp, wm_size;
> > + u32 data = 0;
> > + u32 *txbuf = (u32 *) op->data.buf.out;
>
> You can cast the u8 buffer to u32 and increment it by 1 in each cycle
> below, or you can just use the u8 buffer and align and increment by 8 as
> I did in my proposal for v5.
> I still like my version better as it seems simpler and easier to
> understand ;)
>
> > +
> > + /* clear the TX FIFO. */
> > + fspi_writel(f, FSPI_IPTXFCR_CLR, base + FSPI_IPTXFCR);
> > +
> > + /* Default value of water mark level is 8 bytes. */
> > + wm_size = 8;
> > +
> > + size = op->data.nbytes / wm_size;
> > + for (i = 0; i < size; i++) {
> > + /* Wait for TXFIFO empty */
> > + ret = fspi_readl_poll_tout(f, f->iobase + FSPI_INTR,
> > + FSPI_INTR_IPTXWE, 0,
> > + POLL_TOUT, true);
> > + WARN_ON(ret);
> > +
> > + for (tmp = wm_size, j = 0; tmp > 0; tmp -= 4, j++)
>
> I still think the inner loop should only be added when someone
> implements watermark levels other than 8. It is of no use at the moment
> and makes reading the code more difficult.
> But if you insist on using it, please at least simplify the code.
>
> What about: for (j = 0; j < (wm_size / 4); j++)
>
> > + fspi_writel(f, *txbuf++, base + FSPI_TFDR + j * 4); > +
> > + fspi_writel(f, FSPI_INTR_IPTXWE, base + FSPI_INTR);
> > + }
> > +
> > + size = op->data.nbytes % wm_size;
> > + if (size) {
> > + /* Wait for TXFIFO empty */
> > + ret = fspi_readl_poll_tout(f, f->iobase + FSPI_INTR,
> > + FSPI_INTR_IPTXWE, 0,
> > + POLL_TOUT, true);
> > + WARN_ON(ret);
> > +
> > + for (tmp = size, j = 0; tmp > 0; tmp -= 4, j++) {
>
> Same here: for (j = 0; j < (size / 4); j++) {
>
> > + data = 0;
> > + memcpy(&data, txbuf++, 4);
> > + fspi_writel(f, data, base + FSPI_TFDR + j * 4);
> > + }
> > + fspi_writel(f, FSPI_INTR_IPTXWE, base + FSPI_INTR);
> > + }
> > +}
> > +
> > +static void nxp_fspi_read_rxfifo(struct nxp_fspi *f,
> > + const struct spi_mem_op *op)
> > +{
> > + void __iomem *base = f->iobase;
> > + int i, j;
> > + int size, tmp_size, wm_size, ret;
> > + u32 tmp = 0;
> > + u8 *buf = op->data.buf.in;
> > + u32 len = op->data.nbytes;
> > +
> > + /* Default value of water mark level is 8 bytes. */
> > + wm_size = 8;
> > +
> > + while (len > 0) {
>
> What is this outer loop good for? Below you are first reading aligned to
> wm_size and then the remaining bytes. Why would you need to repeat that?
> It looks like the loop will always be executed only once.
>
> > + size = len / wm_size;
> > + for (i = 0; i < size; i++) {
> > + /* Wait for RXFIFO available */
> > + ret = fspi_readl_poll_tout(f, f->iobase + FSPI_INTR,
> > + FSPI_INTR_IPRXWA, 0,
> > + POLL_TOUT, true);
> > + WARN_ON(ret);
> > +
> > + for (tmp_size = wm_size, j = 0; tmp_size > 0;
> > + tmp_size -= 4, j++, buf += 4) {
>
> What about: for (j = 0; j < (wm_size / 4); j++, buf += 4) {
>
> > + tmp = fspi_readl(f, base + FSPI_RFDR + j * 4);
> > + memcpy(buf, &tmp, 4);
> > + }
> > + /* move the FIFO pointer */
> > + fspi_writel(f, FSPI_INTR_IPRXWA, base + FSPI_INTR);
> > + len -= wm_size;
> > + }
> > +
> > + size = len % wm_size;
> > + if (size) {
> > + /* Wait for RXFIFO available */
> > + ret = fspi_readl_poll_tout(f, f->iobase + FSPI_INTR,
> > + FSPI_INTR_IPRXWA, 0,
> > + POLL_TOUT, true);
> > + WARN_ON(ret);
> > +
> > + for (j = 0; len > 0; len -= size, j++, buf += size) {
> > + tmp = fspi_readl(f, base + FSPI_RFDR + j * 4);
> > + size = len < 4 ? len : 4;
>
> What about: size = min(len, 4);
>
> > + memcpy(buf, &tmp, size);
> > + }
> > + }
> > +
> > + /* invalid the RXFIFO */
> > + fspi_writel(f, FSPI_IPRXFCR_CLR, base + FSPI_IPRXFCR);
> > + /* move the FIFO pointer */
> > + fspi_writel(f, FSPI_INTR_IPRXWA, base + FSPI_INTR);
> > + }
> > +}
>
Once you've addressed all of Frieder's comments you can add
Reviewed-by: Boris Brezillon <bbrezillon@...nel.org>
Regards,
Boris
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