Message-ID: <F2D704DDA6AE8B4A87FF87509480F4A449E02667@CHN-SV-EXMX01.mchp-main.com>
Date:	Wed, 16 Dec 2015 17:35:13 +0000
From:	<Paul.Thacker@...rochip.com>
To:	<andy.green@...aro.org>, <Joshua.Henderson@...rochip.com>
CC:	<linux-kernel@...r.kernel.org>, <linux-mips@...ux-mips.org>,
	<ralf@...ux-mips.org>, <Andrei.Pistirica@...rochip.com>,
	<ulf.hansson@...aro.org>, <jdelvare@...e.de>,
	<geert@...ux-m68k.org>, <cdoban@...adcom.com>,
	<haojian.zhuang@...il.com>, <luisbg@....samsung.com>,
	<Weijun.Yang@....com>, <lokeshvutla@...com>,
	<sbranden@...adcom.com>, <vincent.yang.fujitsu@...il.com>,
	<chaotian.jing@...iatek.com>, <ludovic.desroches@...el.com>,
	<shawn.lin@...k-chips.com>, <sboyd@...eaurora.org>,
	<yangbo.lu@...escale.com>, <haokexin@...il.com>,
	<ben@...adent.org.uk>, <linux-mmc@...r.kernel.org>
Subject: RE: [PATCH v2 12/14] mmc: sdhci-pic32: Add PIC32 SDHCI host
 controller driver

On 12/14/2015 5:33 PM, Andy Green wrote:
> Hi... looks good, just some small general comments.
> 
> On 15 December 2015 at 06:42, Joshua Henderson
> <joshua.henderson@...rochip.com> wrote:
> > From: Andrei Pistirica <andrei.pistirica@...rochip.com>
> >
> > This driver supports the SDHCI host controller found on a PIC32.
> >
> > Signed-off-by: Andrei Pistirica <andrei.pistirica@...rochip.com>
> > Signed-off-by: Joshua Henderson <joshua.henderson@...rochip.com>
> > Cc: Ralf Baechle <ralf@...ux-mips.org>
> > ---
> >  drivers/mmc/host/Kconfig       |   11 ++
> >  drivers/mmc/host/Makefile      |    1 +
> >  drivers/mmc/host/sdhci-pic32.c |  291
> > ++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 303 insertions(+)
> >  create mode 100644 drivers/mmc/host/sdhci-pic32.c
> >
> > diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig index
> > 1dee533..1a3a42b 100644
> > --- a/drivers/mmc/host/Kconfig
> > +++ b/drivers/mmc/host/Kconfig
> > @@ -785,3 +785,14 @@ config MMC_MTK
> >           If you have a machine with a integrated SD/MMC card reader, say Y or M
> here.
> >           This is needed if support for any SD/SDIO/MMC devices is required.
> >           If unsure, say N.
> > +
> > +config MMC_SDHCI_MICROCHIP_PIC32
> > +        tristate "Microchip PIC32MZDA SDHCI support"
> > +        depends on MMC_SDHCI && PIC32MZDA
> > +        help
> > +          This selects the Secure Digital Host Controller Interface (SDHCI)
> > +          for PIC32MZDA platform.
> > +
> > +          If you have a controller with this interface, say Y or M here.
> > +
> > +          If unsure, say N.
> > diff --git a/drivers/mmc/host/Makefile b/drivers/mmc/host/Makefile
> > index 3595f83..af918d2 100644
> > --- a/drivers/mmc/host/Makefile
> > +++ b/drivers/mmc/host/Makefile
> > @@ -75,6 +75,7 @@ obj-$(CONFIG_MMC_SDHCI_BCM2835)               += sdhci-
> bcm2835.o
> >  obj-$(CONFIG_MMC_SDHCI_IPROC)          += sdhci-iproc.o
> >  obj-$(CONFIG_MMC_SDHCI_MSM)            += sdhci-msm.o
> >  obj-$(CONFIG_MMC_SDHCI_ST)             += sdhci-st.o
> > +obj-$(CONFIG_MMC_SDHCI_MICROCHIP_PIC32)        += sdhci-pic32.o
> >
> >  ifeq ($(CONFIG_CB710_DEBUG),y)
> >         CFLAGS-cb710-mmc        += -DDEBUG
> > diff --git a/drivers/mmc/host/sdhci-pic32.c
> > b/drivers/mmc/host/sdhci-pic32.c new file mode 100644 index
> > 0000000..b7d7da2
> > --- /dev/null
> > +++ b/drivers/mmc/host/sdhci-pic32.c
> > @@ -0,0 +1,291 @@
> > +/*
> > + * Support of SDHCI platform devices for Microchip PIC32.
> > + *
> > + * Copyright (C) 2015 Microchip
> > + * Andrei Pistirica, Paul Thacker
> > + *
> > + * Inspired by sdhci-pltfm.c
> > + *
> > + * This file is licensed under the terms of the GNU General Public
> > + * License version 2. This program is licensed "as is" without any
> > + * warranty of any kind, whether express or implied.
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/delay.h>
> > +#include <linux/highmem.h>
> > +#include <linux/module.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/irq.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pm.h>
> > +#include <linux/slab.h>
> > +#include <linux/mmc/host.h>
> > +#include <linux/io.h>
> > +#include "sdhci.h"
> > +#include <linux/platform_data/sdhci-pic32.h>
> > +
> > +#define SDH_SHARED_BUS_CTRL            0x000000E0
> > +#define SDH_SHARED_BUS_NR_CLK_PINS_MASK        0x7
> > +#define SDH_SHARED_BUS_NR_IRQ_PINS_MASK        0x30
> > +#define SDH_SHARED_BUS_CLK_PINS                0x10
> > +#define SDH_SHARED_BUS_IRQ_PINS                0x14
> > +#define SDH_CAPS_SDH_SLOT_TYPE_MASK    0xC0000000
> > +#define SDH_SLOT_TYPE_REMOVABLE                0x0
> > +#define SDH_SLOT_TYPE_EMBEDDED         0x1
> > +#define SDH_SLOT_TYPE_SHARED_BUS       0x2
> > +#define SDHCI_CTRL_CDSSEL              0x80
> > +#define SDHCI_CTRL_CDTLVL              0x40
> > +
> > +#define ADMA_FIFO_RD_THSHLD    512
> > +#define ADMA_FIFO_WR_THSHLD    512
> > +
> > +#define DEV_NAME "pic32-sdhci"
> 
> Is there any point defining this when it only has one use in the driver?

Ack. Will remove.

> 
> > +struct pic32_sdhci_pdata {
> > +       struct platform_device  *pdev;
> > +       struct clk *sys_clk;
> > +       struct clk *base_clk;
> > +};
> > +
> > +static unsigned int pic32_sdhci_get_max_clock(struct sdhci_host
> > +*host) {
> > +       struct pic32_sdhci_pdata *sdhci_pdata = sdhci_priv(host);
> > +
> > +       return clk_get_rate(sdhci_pdata->base_clk);
> > +}
> > +
> > +static void pic32_sdhci_set_bus_width(struct sdhci_host *host, int
> > +width) {
> > +       u8 ctrl;
> > +
> > +       ctrl = sdhci_readb(host, SDHCI_HOST_CONTROL);
> > +       if (width == MMC_BUS_WIDTH_8) {
> > +               ctrl &= ~SDHCI_CTRL_4BITBUS;
> > +               if (host->version >= SDHCI_SPEC_300)
> > +                       ctrl |= SDHCI_CTRL_8BITBUS;
> > +       } else {
> > +               if (host->version >= SDHCI_SPEC_300)
> > +                       ctrl &= ~SDHCI_CTRL_8BITBUS;
> > +               if (width == MMC_BUS_WIDTH_4)
> > +                       ctrl |= SDHCI_CTRL_4BITBUS;
> > +               else
> > +                       ctrl &= ~SDHCI_CTRL_4BITBUS;
> > +       }
> > +       /*
> > +        * SDHCI will not work if JTAG is not Connected.As a workaround fix,
> > +        * set Card Detect Signal Selection bit in SDHCI Host Control
> > +        * register and clear Card Detect Test Level bit in SDHCI Host
> > +        * Control register.
> > +        */
> 
> Isn't this a clearer explanation, if I understood?
> 
> "Without setting CD select and test bits now, SDHCI only works with JTAG
> connected."
> 
> > +       ctrl &= ~SDHCI_CTRL_CDTLVL;
> > +       ctrl |= SDHCI_CTRL_CDSSEL;
> > +       sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);
> 
> Also... is that a feature of the SDHCI IP or this particular chip's implementation
> of it?  I guess if there is only one implementation right now that has that
> restriction worry about making it selectable later.  But if the implementation, it
> might make sense to also put the affected implementation name in the
> comment to make it clear.

This is a chip errata. Having JTAG connected masks the problem, but is otherwise irrelevant. Comment will be changed to: "CD select and test bits must be set for errata workaround."

> 
> > +}
> > +
> > +static unsigned int pic32_sdhci_get_ro(struct sdhci_host *host) {
> > +       /*
> > +        * The SDHCI_WRITE_PROTECT bit is unstable on current hardware so we
> > +        * can't depend on its value in any way.
> > +        */
> > +       return 0;
> > +}
> > +
> > +static const struct sdhci_ops pic32_sdhci_ops = {
> > +       .get_max_clock = pic32_sdhci_get_max_clock,
> > +       .set_clock = sdhci_set_clock,
> > +       .set_bus_width = pic32_sdhci_set_bus_width,
> > +       .reset = sdhci_reset,
> > +       .set_uhs_signaling = sdhci_set_uhs_signaling,
> > +       .get_ro = pic32_sdhci_get_ro,
> > +};
> > +
> > +static void pic32_sdhci_shared_bus(struct platform_device *pdev) {
> > +       struct sdhci_host *host = platform_get_drvdata(pdev);
> > +       u32 bus = readl(host->ioaddr + SDH_SHARED_BUS_CTRL);
> > +       u32 clk_pins = (bus & SDH_SHARED_BUS_NR_CLK_PINS_MASK) >> 0;
> > +       u32 irq_pins = (bus & SDH_SHARED_BUS_NR_IRQ_PINS_MASK) >> 4;
> > +
> > +       /* select first clock */
> > +       if (clk_pins & 0x1)
> 
> BIT(0)?  Also a couple of lines down.
> 
> > +               bus |= (0x1 << SDH_SHARED_BUS_CLK_PINS);
> 
> I know it's popular but there is no meaning or use in "0x1" where you could just
> say "1".
> 
> > +       /* select first interrupt */
> > +       if (irq_pins & 0x1)
> > +               bus |= (0x1 << SDH_SHARED_BUS_IRQ_PINS);
> 
> As above.

Ack. Will change.

> 
> > +       writel(bus, host->ioaddr + SDH_SHARED_BUS_CTRL); }
> > +
> > +static int pic32_sdhci_probe_platform(struct platform_device *pdev,
> > +                                     struct pic32_sdhci_pdata *pdata)
> > +{
> > +       int ret = 0;
> > +       u32 caps_slot_type;
> > +       struct sdhci_host *host = platform_get_drvdata(pdev);
> > +
> > +       /* Check card slot connected on shared bus. */
> > +       host->caps = readl(host->ioaddr + SDHCI_CAPABILITIES);
> > +       caps_slot_type = (host->caps & SDH_CAPS_SDH_SLOT_TYPE_MASK) >>
> 30;
> > +       if (caps_slot_type == SDH_SLOT_TYPE_SHARED_BUS)
> > +               pic32_sdhci_shared_bus(pdev);
> > +
> > +       return ret;
> > +}
> > +
> > +static int pic32_sdhci_probe(struct platform_device *pdev) {
> > +       struct device *dev = &pdev->dev;
> > +       struct sdhci_host *host;
> > +       struct resource *iomem;
> > +       struct pic32_sdhci_pdata *sdhci_pdata;
> > +       struct pic32_sdhci_platform_data *plat_data;
> > +       unsigned int clk_rate = 0;
> > +       int ret;
> > +       struct pinctrl *pinctrl;
> 
> It's hardly critical but for extra gold star arranging local vars in length order
> (longest first) is nice.

Ack.

> 
> > +
> > +       host = sdhci_alloc_host(dev, sizeof(*sdhci_pdata));
> > +       if (IS_ERR(host)) {
> > +               ret = PTR_ERR(host);
> > +               dev_err(&pdev->dev, "cannot allocate memory for sdhci\n");
> > +               goto err;
> > +       }
> > +
> > +       sdhci_pdata = sdhci_priv(host);
> > +       sdhci_pdata->pdev = pdev;
> > +       platform_set_drvdata(pdev, host);
> > +
> > +       iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +       host->ioaddr = devm_ioremap_resource(&pdev->dev, iomem);
> > +       if (IS_ERR(host->ioaddr)) {
> > +               ret = PTR_ERR(host->ioaddr);
> > +               dev_err(&pdev->dev, "unable to map iomem: %d\n", ret);
> > +               goto err_host;
> > +       }
> > +
> > +       plat_data = pdev->dev.platform_data;
> > +       if (plat_data && plat_data->setup_dma) {
> > +               ret = plat_data->setup_dma(ADMA_FIFO_RD_THSHLD,
> > +                                          ADMA_FIFO_WR_THSHLD);
> > +               if (ret)
> > +                       goto err_host;
> > +       }
> > +
> > +       pinctrl = devm_pinctrl_get_select_default(&pdev->dev);
> > +       if (IS_ERR(pinctrl)) {
> > +               ret = PTR_ERR(pinctrl);
> > +               dev_warn(&pdev->dev, "No pinctrl provided %d\n", ret);
> > +               if (ret == -EPROBE_DEFER)
> > +                       goto err_host;
> > +       }
> > +
> > +       host->ops = &pic32_sdhci_ops;
> > +       host->irq = platform_get_irq(pdev, 0);
> > +
> > +       sdhci_pdata->sys_clk = devm_clk_get(&pdev->dev, "sys_clk");
> > +       if (IS_ERR(sdhci_pdata->sys_clk)) {
> > +               ret = PTR_ERR(sdhci_pdata->sys_clk);
> > +               dev_err(&pdev->dev, "Error getting clock\n");
> > +               goto err_host;
> > +       }
> > +
> > +       /* Enable clock when available! */
> > +       ret = clk_prepare_enable(sdhci_pdata->sys_clk);
> > +       if (ret) {
> > +               dev_dbg(&pdev->dev, "Error enabling clock\n");
> 
> Shouldn't this be dev_err()?  You don't survive not having the clock in the stanza
> above.  So if you have the clock, you would want to know if it didn't deal with
> the clk_prepare_enable().
> 
> The comment 4 lines above is also wrong if so.

Ack. 

> 
> > +               goto err_host;
> > +       }
> > +
> > +       /* SDH CLK enable */
> > +       sdhci_pdata->base_clk = devm_clk_get(&pdev->dev, "base_clk");
> > +       if (IS_ERR(sdhci_pdata->base_clk)) {
> > +               ret = PTR_ERR(sdhci_pdata->base_clk);
> > +               dev_err(&pdev->dev, "Error getting clock\n");
> > +               goto err_host;
> > +       }
> > +
> > +       /* Enable clock when available! */
> > +       ret = clk_prepare_enable(sdhci_pdata->base_clk);
> 
> Again the comment seems wrong.

Ack.

> 
> > +       if (ret) {
> > +               dev_dbg(&pdev->dev, "Error enabling clock\n");
> 
> And if I understood it, dev_err() needed.

Ack.

> 
> > +               goto err_host;
> > +       }
> > +
> > +       clk_rate = clk_get_rate(sdhci_pdata->base_clk);
> > +       dev_dbg(&pdev->dev, "base clock at: %u\n", clk_rate);
> > +       clk_rate = clk_get_rate(sdhci_pdata->sys_clk);
> > +       dev_dbg(&pdev->dev, "sys clock at: %u\n", clk_rate);
> > +
> > +       host->quirks2 |= SDHCI_QUIRK2_NO_1_8_V;
> > +
> 
> Probably can lose the blank line.

Ack.

> 
> > +       host->quirks |= SDHCI_QUIRK_NO_HISPD_BIT;
> > +
> > +       ret = mmc_of_parse(host->mmc);
> > +       if (ret)
> > +               goto err_host;
> > +
> > +       ret = pic32_sdhci_probe_platform(pdev, sdhci_pdata);
> > +       if (ret) {
> > +               dev_err(&pdev->dev, "failed to probe platform!\n");
> > +               goto err_host;
> > +       }
> > +
> > +       ret = sdhci_add_host(host);
> > +       if (ret) {
> > +               dev_dbg(&pdev->dev, "error adding host\n");
> > +               goto err_host;
> > +       }
> > +
> > +       dev_info(&pdev->dev, "Successfully added sdhci host\n");
> > +       return 0;
> > +
> > +err_host:
> > +       sdhci_free_host(host);
> > +err:
> > +       dev_err(&pdev->dev, "pic32-sdhci probe failed: %d\n", ret);
> > +       return ret;
> > +}
> > +
> > +static int pic32_sdhci_remove(struct platform_device *pdev) {
> > +       struct sdhci_host *host = platform_get_drvdata(pdev);
> > +       struct pic32_sdhci_pdata *sdhci_pdata = sdhci_priv(host);
> > +       int dead = 0;
> > +       u32 scratch;
> > +
> > +       scratch = readl(host->ioaddr + SDHCI_INT_STATUS);
> > +       if (scratch == (u32)-1)
> 
> Since it's not actually related to signed, (u32)~0 might be clearer.

Ack.

> 
> > +               dead = 1;
> > +
> > +       sdhci_remove_host(host, dead);
> 
> You could get rid of "dead" and have
> 
>          sdhci_remove_host(host, scratch == (u32)~0);

Ack. 

> 
> > +       clk_disable_unprepare(sdhci_pdata->base_clk);
> > +       clk_disable_unprepare(sdhci_pdata->sys_clk);
> > +       sdhci_free_host(host);
> > +
> > +       return 0;
> > +}
> > +
> > +static const struct of_device_id pic32_sdhci_id_table[] = {
> > +       { .compatible = "microchip,pic32mzda-sdhci" },
> > +       {}
> > +};
> > +MODULE_DEVICE_TABLE(of, pic32_sdhci_id_table);
> > +
> > +static struct platform_driver pic32_sdhci_driver = {
> > +       .driver = {
> > +               .name   = DEV_NAME,
> > +               .owner  = THIS_MODULE,
> > +               .of_match_table = of_match_ptr(pic32_sdhci_id_table),
> > +       },
> > +       .probe          = pic32_sdhci_probe,
> > +       .remove         = pic32_sdhci_remove,
> > +};
> > +
> > +module_platform_driver(pic32_sdhci_driver);
> > +
> > +MODULE_DESCRIPTION("Microchip PIC32 SDHCI driver");
> > +MODULE_AUTHOR("Pistirica Sorin Andrei & Sandeep Sheriker");
> > +MODULE_LICENSE("GPL v2");
> > --
> > 1.7.9.5
> >

Thanks,
Paul

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