Date:	Tue, 26 Apr 2016 15:29:22 +0200
From:	Ludovic Desroches <ludovic.desroches@...el.com>
To:	Prabu Thangamuthu <Prabu.T@...opsys.com>
CC:	Jaehoon Chung <jh80.chung@...sung.com>,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	"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>,
	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>,
	CPGS <cpgs@...sung.com>
Subject: Re: [PATCH v3] mmc: sdhci-pci: add Support of Synopsys DWC_MSHC IP

On Tue, Apr 26, 2016 at 12:31:50PM +0000, Prabu Thangamuthu wrote:
> Hi Ludovic, Jaehoon Chung,
> 
> Thank you for your review comments,
> 
> On 04/26/2016 04:15 PM, Jaehoon Chung wrote:
> > 
> > On 04/26/2016 05:58 PM, Ludovic Desroches wrote:
> > > On Wed, Apr 20, 2016 at 12:22:59PM +0000, Prabu Thangamuthu wrote:
> > >> Patch for Standard SD Host Controller Interface compliant Synopsys
> > >> sdhci-dwc controller driver. This code supports PCI based interface.
> > >>
> > >> Signed-off-by: Prabu Thangamuthu <prabu.t@...opsys.com>
> > >> ---
> > >> Change log v3:
> > >> 	-Removed unused code.
> > >> 	-Updated review comments.
> > >>
> > >> Change log v2:
> > >> 	-Removed Synopsys specific PCI device ID's from pci_ids.h.
> > >> 	-Updated the PCI device ID's in sdhci-pci-core.c.
> > >>
> > >>  MAINTAINERS                       |   7 +
> > >>  drivers/mmc/host/Makefile         |   3 +-
> > >>  drivers/mmc/host/sdhci-pci-core.c |  14 ++
> > >> drivers/mmc/host/sdhci-pci-dwc.c  | 260
> > >> ++++++++++++++++++++++++++++++++++++++
> > >>  drivers/mmc/host/sdhci-pci-dwc.h  |  55 ++++++++
> > >>  5 files changed, 338 insertions(+), 1 deletion(-)  create mode
> > >> 100644 drivers/mmc/host/sdhci-pci-dwc.c  create mode 100644
> > >> drivers/mmc/host/sdhci-pci-dwc.h
> > >>

[snip]

> > >> diff --git a/drivers/mmc/host/sdhci-pci-dwc.c
> > >> b/drivers/mmc/host/sdhci-pci-dwc.c
> > >> new file mode 100644
> > >> index 0000000..3490af8
> > >> --- /dev/null
> > >> +++ b/drivers/mmc/host/sdhci-pci-dwc.c
> > >> @@ -0,0 +1,260 @@
> > >> +/*
> > >> + * 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.
> > >> + *
> > >> + */
> > >> +
> > >> +#include <linux/pci.h>
> > >> +#include <linux/delay.h>
> > >> +#include <linux/module.h>
> > >> +#include <linux/moduleparam.h>
> > >> +
> > >> +#include "sdhci.h"
> > >> +#include "sdhci-pci.h"
> > >> +#include "sdhci-pci-dwc.h"
> > >> +
> > >>
> > +/*********************************************************
> > ********************\
> > >> + *                                                                           *
> > >> + * Hardware specific clock handling                                          *
> > >> + *                                                                           *
> > >>
> > +\*********************************************************
> > ********************/
> > >> +static const struct sdhci_ops *sdhci_ops;	/* Low level hw interface */
> > >> +

[snip]

> > >> +static void sdhci_set_clock_snps(struct sdhci_host *host,
> > >> +						unsigned int clock)
> > >> +{
> > >> +	int div = 0;
> > >> +	int mul = 0;
> > >> +	int div_val = 0;
> > >> +	int mul_val = 0;
> > >> +	int mul_div_val = 0;
> > >> +	u32 reg = 0;
> > >> +	u16 clk = 0;
> > >> +	u16 vendor_ptr = 0;
> > >> +	u32 mask = 0;
> > >> +	unsigned long timeout;
> > >> +	u32 tx_clk_phase_val = SDHC_DEF_TX_CLK_PH_VAL;
> > >> +	u32 rx_clk_phase_val = SDHC_DEF_RX_CLK_PH_VAL;
> > >> +
> > >
> > > Some variables don't need to be initialized here.
> > 
> > tx/rx_clk_phase_val don't need?
> > i didn't see any modifying these vales.
> > 
> > And some variables don't need to define..can be reused.
> >
> OK, We will update it accordingly.
>  
> > >
> > >> +	/*
> > >> +	 * if clock is less than 25MHz, divided clock is used.
> > >> +	 * For divided clock, we can use the standard sdhci_set_clock().
> > >> +	 * For clock above 25MHz, DRP clock is used
> > >> +	 * Here, we cannot use sdhci_set_clock(), we need to program
> > >> +	 * TX RX CLOCK DCM DRP for appropriate clock
> > >> +	 */
> > >> +
> > >> +	if (clock <= 25000000) {
> > >> +		/* Then call generic set_clock */
> > >> +		if (sdhci_ops->set_clock)
> > >> +			sdhci_ops->set_clock(host, clock);
> > >
> > > I am not sure about this part. You may simply call sdhci_set_clock()
> > > instead of sdhci_ops->set_clock(). See my latest comment, it is not
> > > clear what is behind set_clock().
> > >
> 
> As we have built our own clocking logic using DCM, we want to use our
> own set_clock function for the frequency above 25MHz.
> For lower frequencies, our clocking module program is same as sdhci_set_clock().
> So we are calling sdhci_ops->set_clock() which is same as sdhci_set_clock().
> 
> > >> +	} else {
> > >> +
> > >> +		host->mmc->actual_clock = 0;
> > >> +		vendor_ptr = sdhci_readw(host, SDHCI_UHS2_VENDOR);
> > >> +
> > >> +		/* Select un-phase shifted clock before reset Tx Tuning
> > DCM*/
> > >> +		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);
> > >> +
> > >> +		sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> > >> +
> > >> +		/* Lets chose the Mulitplier value to be 0x2 */
> > >> +		mul = 0x2;
> > >> +		for (div = 1; div <= 32; div++) {
> > >> +			if (((host->max_clk * mul) / div)
> > >> +					<= clock)
> > >> +				break;
> > >> +		}
> > >> +		/*
> > >> +		 * Set Programmable Clock Mode in the Clock
> > >> +		 * Control register.
> > >> +		 */
> > >> +		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
> > >> +		 */
> > >> +
> > >> +		mask = SDHC_CARD_TX_CLK_DCM_RST;
> > >> +		snps_reset_dcm(host, mask, 1);
> > >> +
> > >> +		mul_div_val = (mul_val << 8) | div_val;
> > >> +		sdhci_writew(host, mul_div_val,
> > TXRX_CLK_DCM_MUL_DIV_DRP);
> > >> +
> > >> +		reg = sdhci_readl(host, TXRX_CLK_DCM_DRP_BASE_51);
> > >> +
> > >> +		snps_reset_dcm(host, mask, 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) {
> > >> +				pr_err("%s: Internal clock never stabilised\n",
> > >> +						mmc_hostname(host-
> > >mmc));
> > >> +				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
> > >> +		 */
> > >> +
> > >> +		mask = SDHC_TUNING_TX_CLK_DCM_RST |
> > SDHC_TUNING_RX_CLK_DCM_RST;
> > >> +		snps_reset_dcm(host, mask, 1);
> > >> +		mdelay(10);
> > >> +		snps_reset_dcm(host, mask, 0);
> > >> +
> > >> +		/* Select working phase value if clock is <= 50MHz */
> > >> +		if (clock <= 50000000) {
> > >> +			/*Change the Tx Phase value here */
> > >> +			reg = sdhci_readl(host, (SDHC_GPIO_OUT +
> > vendor_ptr));
> > >> +			reg |= (SDHC_TUNING_TX_CLK_SEL_MASK &
> > >> +			   (tx_clk_phase_val <<
> > SDHC_TUNING_TX_CLK_SEL_SHIFT));
> > >> +
> > >> +			sdhci_writel(host, reg, (SDHC_GPIO_OUT +
> > vendor_ptr));
> > >> +			mdelay(10);
> > >> +
> > >> +			/* 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 &
> > >> +					rx_clk_phase_val);
> > >> +			sdhci_writel(host, reg, (SDHC_DBOUNCE +
> > vendor_ptr));
> > >> +		}
> > >> +		mdelay(10);
> > >> +	}
> > >> +}

[snip]

> > >> +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;
> > >> +
> > >> +	host = slot->host;
> > >> +	sdhci_ops = host->ops;
> > >> +
> > >> +	sdhci_pci_ops_snps.enable_dma		= sdhci_ops-
> > >enable_dma;
> > >> +	sdhci_pci_ops_snps.set_bus_width	= sdhci_ops->set_bus_width;
> > >> +	sdhci_pci_ops_snps.reset		= sdhci_ops->reset;
> > >> +	sdhci_pci_ops_snps.set_uhs_signaling	= sdhci_ops-
> > >set_uhs_signaling;
> > >> +	sdhci_pci_ops_snps.hw_reset		= sdhci_ops->hw_reset;
> > >> +
> > >> +	host->ops = &sdhci_pci_ops_snps;
> > >
> > > I am lost. sdhci_ops is a kind of backup of the original ops from pci
> > > core. Your sdhci_pci_ops_snps is a copy of ops from pci core excepting
> > > set_clock and finally you update pci core ops with sdhci_pci_ops_snps.
> > >
> > > It seems a bit complex. At the end, unless I have missed something,
> > > you have only changed set_clock from pci ops.
> > >
> 
> You are correct, sdhci_pci_ops_snps is using pci core ops except set_clock.
> As I mentioned at the top, We have built our own clocking logic using DCM. 
> So, we have to use our own set_clock function and We are reusing the pci core
> ops for the reaming ops.

Ok so I have well understood. Any reason to not do it this way:


-static const struct sdhci_ops *sdhci_ops;

-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;
+
+        host = slot->host;
+        host->ops->set_clock = &sdhci_set_clock_snps;

And use sdhci_set_clock() instead of sdhci_ops->set_clock. At the first read,
I thought you are not calling sdhci_set_clock() but sdhci_set_clock_snps()
but I understood later that sdhci_ops is different from host->ops which
is a bit confusing.

Regards

Ludovic

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