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Date: Thu, 28 Apr 2016 08:35:34 +0000
From: Prabu Thangamuthu <Prabu.T@...opsys.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>,
Prabu Thangamuthu <Prabu.T@...opsys.com>
CC: "Ulf Hansson (ulf.hansson@...aro.org)" <ulf.hansson@...aro.org>,
"Adrian Hunter" <adrian.hunter@...el.com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
"David S. Miller" <davem@...emloft.net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
"Kalle Valo" <kvalo@...eaurora.org>,
Mauro Carvalho Chehab <mchehab@....samsung.com>,
Guenter Roeck <linux@...ck-us.net>,
Jiri Slaby <jslaby@...e.com>,
"Chaotian Jing" <chaotian.jing@...iatek.com>,
Andrei Pistirica <andrei.pistirica@...rochip.com>,
Ben Hutchings <ben.hutchings@...ethink.co.uk>,
Joshua Henderson <joshua.henderson@...rochip.com>,
Ludovic Desroches <ludovic.desroches@...el.com>,
Manjunath M Bettegowda <Manjunath.MB@...opsys.com>,
"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v4] mmc: sdhci-pci: add Support of Synopsys DWC_MSHC IP
Hi Andy Shevchenko,
On 04/27/2016 7:09 PM, Andy Shevchenko wrote:
>
> On Wed, Apr 27, 2016 at 2:51 PM, Prabu Thangamuthu
> <Prabu.T@...opsys.com> 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@...opsys.com>
>
> Authors
>
> > + * Prabu Thangamuthu <prabu.t@...opsys.com>
> > + *
> > + * 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.
This for loop is exactly taken from drivers/mmc/host/sdhci.c
We want to maintain the consistency between our file and sdhci.c
>
> 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.
This while loop also exactly taken from drivers/mmc/host/sdhci.c (function name sdhci_set_clock).
We want to maintain the consistency between our file and sdhci.c for easy readability.
>
> 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
I didn't get any warning/error when I ran scripts/checkpatch.pl against my patch.
Did you find this "Space" issue by manual check or by running any scripts?
>
> > + 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@...opsys.com>
> > + *
> > + * 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
> >
Thanks for above points. We will update it.
Regards,
Prabu Thangamuthu.
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