Re: [PATCH v4] mmc: sdhci-pci: add Support of Synopsys DWC_MSHC IP

From: Andy Shevchenko
Date: Wed Apr 27 2016 - 09:39:28 EST

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In reply to: Prabu Thangamuthu: "[PATCH v4] mmc: sdhci-pci: add Support of Synopsys DWC_MSHC IP"
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On Wed, Apr 27, 2016 at 2:51 PM, Prabu Thangamuthu <Prabu.T@xxxxxxxxxxxx> wrote:
> Patch for Standard SD Host Controller Interface compliant Synopsys
> sdhci-dwc controller driver. This code supports PCI based interface.

> @@ -0,0 +1,244 @@
> +/*
> + * Copyright (C) 2016 Synopsys, Inc.
> + *
> + * Author: Manjunath M B <manjumb@xxxxxxxxxxxx>

Authors

> + * Prabu Thangamuthu <prabu.t@xxxxxxxxxxxx>
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + */

> +/*****************************************************************************\
> + * *
> + * Hardware specific clock handling *
> + * *
> +\*****************************************************************************/

Most of the lines are non-informative.

> +static void snps_reset_dcm(struct sdhci_host *host, u32 mask, u8 reset)
> +{
> + u16 vendor_ptr;
> + u32 reg;
> +
> + vendor_ptr = sdhci_readw(host, SDHCI_UHS2_VENDOR);
> +
> + reg = sdhci_readl(host, (SDHC_GPIO_OUT + vendor_ptr));
> +
> + if (reset == 1)
> + reg |= mask;
> + else
> + reg &= ~mask;
> +
> + sdhci_writel(host, reg, (SDHC_GPIO_OUT + vendor_ptr));
> +}
> +
> +static void sdhci_set_clock_snps(struct sdhci_host *host, u32 clock)
> +{
> + u8 div;
> + u8 mul;

I understand that CodingStyle recommends to keep one variable by line,
but here might be useful to combine related variables

u8 mul, div;

> + u8 div_val;
> + u8 mul_val;

u8 mul_val, div_val;

Up to you and to maintainers.

> + u8 timeout;
> + u16 clk;
> + u16 vendor_ptr;
> + u16 mul_div_val;
> + u32 reg;
> +
> + /*
> + * if clock is less than 25MHz, divided clock is used.

if -> If

> + * For divided clock, we can use the standard sdhci_set_clock().
> + * For clock above 25MHz, DRP clock is used

Dot.

> + * Here, we cannot use sdhci_set_clock(), we need to program
> + * TX RX CLOCK DCM DRP for appropriate clock

Ditto.

> + */

> +

Redundant.

> + if (clock <= 25000000) {
> + /* Then call standard set_clock */
> + sdhci_set_clock(host, clock);

> + } else {

You may save indentation if you return directly in positive branch.

> +
> + host->mmc->actual_clock = 0;
> + vendor_ptr = sdhci_readw(host, SDHCI_UHS2_VENDOR);
> +
> + /* Select un-phase shifted clock before reset Tx Tuning DCM*/

Space is missed

> + reg = sdhci_readl(host, (SDHC_GPIO_OUT + vendor_ptr));
> + reg &= ~SDHC_TX_CLK_SEL_TUNED;
> + sdhci_writel(host, reg, (SDHC_GPIO_OUT + vendor_ptr));

> + mdelay(10);

Why?! Explanation is needed.

> +
> + sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> +
> + /* Lets chose the Mulitplier value to be 0x2 */

Lets -> Let's

No explanation why so?

> + mul = 0x2;
> + for (div = 1; div <= 32; div++) {
> + if (((host->max_clk * mul) / div)
> + <= clock)

Too many parens.

> + break;
> + }

So, you would like to find a minimum divider that guarantees the
clock > max_clk * mul / div.

This is completely long way to achieve.

What about
div = DIV_ROUND_UP(max_clk * mul / clock)

div_val = max(div, 32);

> + /*
> + * Set Programmable Clock Mode in the Clock
> + * Control register.
> + */

I suppose one line after fixing indentation.

> + div_val = div - 1;
> + mul_val = mul - 1;
> +
> + host->mmc->actual_clock = (host->max_clk * mul) / div;
> + /*
> + * Program the DCM DRP
> + * Step 1: Assert DCM Reset
> + * Step 2: Program the mul and div values in DRP
> + * Step 3: Read from DRP base 0x00 to restore DCM output as per
> + * www.xilinx.com/support/documentation/user_guides/ug191.pdf
> + * Step 4: De-Assert reset to DCM
> + */
> +
> + snps_reset_dcm(host, SDHC_CARD_TX_CLK_DCM_RST, 1);
> +
> + mul_div_val = (mul_val << 8) | div_val;
> + sdhci_writew(host, mul_div_val, TXRX_CLK_DCM_MUL_DIV_DRP);
> + sdhci_readl(host, TXRX_CLK_DCM_DRP_BASE_51);
> +
> + snps_reset_dcm(host, SDHC_CARD_TX_CLK_DCM_RST, 0);
> +
> + clk = SDHCI_PROG_CLOCK_MODE | SDHCI_CLOCK_INT_EN;
> + sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> +
> + /* Wait max 20 ms */
> + timeout = 20;
> + while (!((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
> + & SDHCI_CLOCK_INT_STABLE)) {
> + if (timeout == 0) {

This is invariant to the loop. Check how it's done in other drivers.

Something like

while (condition && --timeout) {
...
}
if (!timeout) {
...
}

> + pr_err("%s: Internal clock never stabilised\n",
> + mmc_hostname(host->mmc));

dev_err() ?

> + return;
> + }
> + timeout--;
> + mdelay(1);
> + }
> +
> + clk |= SDHCI_CLOCK_CARD_EN;
> + sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> +
> + /*
> + * This Clock might have affected the TX CLOCK DCM and RX CLOCK
> + * DCM which are used for Phase control; Reset these DCM's
> + * for proper clock output
> + *
> + * Step 1: Reset the DCM
> + * Step 2: De-Assert reset to DCM
> + */
> +
> + snps_reset_dcm(host, SDHC_TUNING_TX_CLK_DCM_RST |
> + SDHC_TUNING_RX_CLK_DCM_RST, 1);
> + mdelay(10);
> + snps_reset_dcm(host, SDHC_TUNING_TX_CLK_DCM_RST |
> + SDHC_TUNING_RX_CLK_DCM_RST, 0);
> +
> + /* Select working phase value if clock is <= 50MHz */
> + if (clock <= 50000000) {
> + /*Change the Tx Phase value here */

Space

> + reg = sdhci_readl(host, (SDHC_GPIO_OUT + vendor_ptr));
> + reg |= (SDHC_TUNING_TX_CLK_SEL_MASK &
> + (SDHC_DEF_TX_CLK_PH_VAL <<
> + SDHC_TUNING_TX_CLK_SEL_SHIFT));
> +
> + sdhci_writel(host, reg, (SDHC_GPIO_OUT + vendor_ptr));

> + mdelay(10);

Why?!

> +
> + /* Program to select phase shifted clock */
> + reg |= SDHC_TX_CLK_SEL_TUNED;
> + sdhci_writel(host, reg, (SDHC_GPIO_OUT + vendor_ptr));
> +
> + /*
> + * For 50Mhz, tuning is not possible.
> + * Lets fix the sampling Phase of Rx Clock here.
> + */
> + reg = sdhci_readl(host, (SDHC_DBOUNCE + vendor_ptr));
> + reg &= ~SDHC_TUNING_RX_CLK_SEL_MASK;
> + reg |= (SDHC_TUNING_RX_CLK_SEL_MASK &
> + SDHC_DEF_RX_CLK_PH_VAL);
> + sdhci_writel(host, reg, (SDHC_DBOUNCE + vendor_ptr));
> + }
> + mdelay(10);

Ditto.

> + }
> +}

Don't have time to go further. Check your code fully and carefully.

> +
> +static int snps_init_clock(struct sdhci_host *host)
> +{
> + u16 mul_div_val;
> +
> + /*
> + * Configure the BCLK DRP to get 100 MHZ Clock
> + * To get 100MHz from 100MHz input freq,
> + * mul=1 and div=1
> + * Formula: output_clock = (input clock * mul) / div
> + *
> + * Program the DCM DRP
> + * Step 1: Assert DCM Reset
> + * Step 2: Program the mul and div values in DRP
> + * Step 3: Read from DRP base 0x00 to restore DCM output as per
> + * www.xilinx.com/support/documentation/user_guides/ug191.pdf
> + * Step 4: De-Assert reset to DCM
> + */
> + snps_reset_dcm(host, SDHC_BCLK_DCM_RST, 1);
> +
> + mul_div_val = 0x0101;
> + sdhci_writew(host, mul_div_val, BCLK_DCM_MUL_DIV_DRP);
> + sdhci_readl(host, BCLK_DCM_DRP_BASE_51);
> +
> + snps_reset_dcm(host, SDHC_BCLK_DCM_RST, 0);
> +
> + /*
> + * By Default Clocks to Controller are OFF.
> + * Before stack applies reset; we need to turn on the clock
> + */
> + sdhci_writew(host, SDHCI_CLOCK_INT_EN, SDHCI_CLOCK_CONTROL);
> +
> + return 0;
> +
> +}
> +static struct sdhci_ops sdhci_pci_ops_snps = {
> + .set_clock = sdhci_set_clock_snps,
> +};
> +
> +int sdhci_pci_probe_slot_snps(struct sdhci_pci_slot *slot)
> +{
> + int ret = 0;
> + struct sdhci_host *host;
> + const struct sdhci_ops *sdhci_pci_ops; /* Low level hw interface */
> +
> + host = slot->host;
> + sdhci_pci_ops = host->ops;
> +
> + sdhci_pci_ops_snps.enable_dma = sdhci_pci_ops->enable_dma;
> + sdhci_pci_ops_snps.set_bus_width = sdhci_pci_ops->set_bus_width;
> + sdhci_pci_ops_snps.reset = sdhci_pci_ops->reset;
> + sdhci_pci_ops_snps.set_uhs_signaling =
> + sdhci_pci_ops->set_uhs_signaling;
> + sdhci_pci_ops_snps.hw_reset = sdhci_pci_ops->hw_reset;
> + sdhci_pci_ops_snps.select_drive_strength =
> + sdhci_pci_ops->select_drive_strength;
> +
> + host->ops = &sdhci_pci_ops_snps;
> +
> + /* Board specific clock initialization */
> + ret = snps_init_clock(host);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(sdhci_pci_probe_slot_snps);
> diff --git a/drivers/mmc/host/sdhci-pci-dwc.h b/drivers/mmc/host/sdhci-pci-dwc.h
> new file mode 100644
> index 0000000..02e2213
> --- /dev/null
> +++ b/drivers/mmc/host/sdhci-pci-dwc.h
> @@ -0,0 +1,55 @@
> +/*
> + * Copyright (C) 2016 Synopsys, Inc.
> + *
> + * Author: Manjunath M B <manjumb@xxxxxxxxxxxx>
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#ifndef __SDHCI_DWC_MSHC_PCI_H__
> +#define __SDHCI_DWC_MSHC_PCI_H__
> +
> +#include "sdhci-pci.h"
> +
> +#define SDHCI_UHS2_VENDOR 0xE8
> +
> +#define DRIVER_NAME "sdhci-pci-dwc"
> +#define SDHC_DEF_TX_CLK_PH_VAL 4
> +#define SDHC_DEF_RX_CLK_PH_VAL 4
> +
> +/* Synopsys Vendor Specific Registers */
> +#define SDHC_DBOUNCE 0x08
> +#define SDHC_TUNING_RX_CLK_SEL_MASK 0x000000FF
> +#define SDHC_GPIO_OUT 0x34
> +/* HAPS 51 Based implementation */
> +#define SDHC_BCLK_DCM_RST 0x00000001
> +#define SDHC_CARD_TX_CLK_DCM_RST 0x00000002
> +#define SDHC_TUNING_RX_CLK_DCM_RST 0x00000004
> +#define SDHC_TUNING_TX_CLK_DCM_RST 0x00000008
> +#define SDHC_TUNING_TX_CLK_SEL_MASK 0x00000070
> +#define SDHC_TUNING_TX_CLK_SEL_SHIFT 4
> +#define SDHC_TX_CLK_SEL_TUNED 0x00000080
> +
> +/* Offset of BCLK DCM DRP Attributes */
> +/* Every attribute is of 16 bit wide */
> +#define BCLK_DCM_DRP_BASE_51 0x1000
> +
> +#define BCLK_DCM_MUL_DIV_DRP 0x1050
> +#define MUL_MASK_DRP 0xFF00
> +#define DIV_MASK_DRP 0x00FF
> +
> +/* Offset of TX and RX CLK DCM DRP */
> +#define TXRX_CLK_DCM_DRP_BASE_51 0x2000
> +#define TXRX_CLK_DCM_MUL_DIV_DRP 0x2050
> +
> +int sdhci_pci_probe_slot_snps(struct sdhci_pci_slot *slot);
> +
> +#endif
> --
> 1.9.1
>

--
With Best Regards,
Andy Shevchenko

Next message: Boris Ostrovsky: "Re: [Xen-devel] [PATCH] xen/x86: actually allocate legacy interrupts on PV guests"
Previous message: Corey Minyard: "Re: [PATCH] IPMI: reserve memio regions separately"
In reply to: Prabu Thangamuthu: "[PATCH v4] mmc: sdhci-pci: add Support of Synopsys DWC_MSHC IP"
Next in thread: Prabu Thangamuthu: "RE: [PATCH v4] mmc: sdhci-pci: add Support of Synopsys DWC_MSHC IP"
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