linux-kernel - Re: [PATCH v3] mmc: sdhci-pci: add Support of Synopsys DWC

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Message-ID: <20160426090522.GB8756@odux.rfo.atmel.com>
Date:	Tue, 26 Apr 2016 11:05:22 +0200
From:	Ludovic Desroches <ludovic.desroches@...el.com>
To:	Prabu Thangamuthu <Prabu.T@...opsys.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>
Subject: Re: [PATCH v3] mmc: sdhci-pci: add Support of Synopsys DWC_MSHC IP

On Tue, Apr 26, 2016 at 10:58:45AM +0200, 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]

> > +static int snps_init_clock(struct sdhci_host *host)
> > +{
> > +	int div = 0;
> > +	int mul = 0;
> > +	int div_val = 0;
> > +	int mul_val = 0;
> > +	int mul_div_val = 0;
> > +	int reg = 0;
> > +	u32 mask = 0;
> > +
> 
> Some variables don't need initialization here or you can directly assign
> the right value: int div = 2, mul = 2, etc.

div and mul are even useless, they are const. You can directly declare
mul_val = 1, div_val = 1.

Regards

Ludovic

> 
> > +	/* Configure the BCLK DRP to get 100 MHZ Clock */
> > +
> > +	/*
> > +	 * To get 100MHz from 100MHz input freq,
> > +	 * mul=2 and div=2
> > +	 * Formula: output_clock = (input clock * mul) / div
> > +	 */
> > +	mul = 2;
> > +	div = 2;
> > +	mul_val = mul - 1;
> > +	div_val = div - 1;
> > +	/*
> > +	 * 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_BCLK_DCM_RST;
> > +	snps_reset_dcm(host, mask, 1);
> > +
> > +	mul_div_val = (mul_val << 8) | div_val;
> > +	sdhci_writew(host, mul_div_val, BCLK_DCM_MUL_DIV_DRP);
> > +
> > +	reg = sdhci_readl(host, BCLK_DCM_DRP_BASE_51);
> > +
> > +	snps_reset_dcm(host, mask, 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;
> > +
> > +}