linux-mips
[Top] [All Lists]

Re: [PATCH V3 06/10] MIPS: lantiq: add NOR flash support

To: John Crispin <blogic@openwrt.org>
Subject: Re: [PATCH V3 06/10] MIPS: lantiq: add NOR flash support
From: Sergei Shtylyov <sshtylyov@mvista.com>
Date: Fri, 04 Mar 2011 15:41:14 +0300
Cc: Ralf Baechle <ralf@linux-mips.org>, Ralph Hempel <ralph.hempel@lantiq.com>, David Woodhouse <dwmw2@infradead.org>, Daniel Schwierzeck <daniel.schwierzeck@googlemail.com>, linux-mips@linux-mips.org, linux-mtd@lists.infradead.org
In-reply-to: <1299146626-17428-7-git-send-email-blogic@openwrt.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <1299146626-17428-1-git-send-email-blogic@openwrt.org> <1299146626-17428-7-git-send-email-blogic@openwrt.org>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.2.14) Gecko/20110221 Thunderbird/3.1.8
Hello.

On 03-03-2011 13:03, John Crispin wrote:

NOR flash is attached to the same EBU (External Bus Unit) as PCI. As described
in the PCI patch, the EBU is a little buggy, resulting in the upper and lower
16 bit of the data on a 32 bit read are swapped. (essentially we have a addr^=2)

   "Are" not needed.

To work around this we do a addr^=2 during the probe. Once probed we adapt
cfi->addr_unlock1 and cfi->addr_unlock2 to represent the endianess bug.

Signed-off-by: John Crispin<blogic@openwrt.org>
Signed-off-by: Ralph Hempel<ralph.hempel@lantiq.com>
Cc: David Woodhouse<dwmw2@infradead.org>
Cc: Daniel Schwierzeck<daniel.schwierzeck@googlemail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-mtd@lists.infradead.org
[...]

diff --git a/drivers/mtd/maps/Kconfig b/drivers/mtd/maps/Kconfig
index 5d37d31..587468e 100644
--- a/drivers/mtd/maps/Kconfig
+++ b/drivers/mtd/maps/Kconfig
@@ -260,6 +260,13 @@ config MTD_BCM963XX
          Support for parsing CFE image tag and creating MTD partitions on
          Broadcom BCM63xx boards.

+config MTD_LANTIQ
+       bool "Lantiq SoC NOR support"
+       depends on LANTIQ && MTD_PARTITIONS

   Maybe you should select MTD_PARTITIONS instead?

[...]
diff --git a/drivers/mtd/maps/lantiq.c b/drivers/mtd/maps/lantiq.c
new file mode 100644
index 0000000..674be0a
--- /dev/null
+++ b/drivers/mtd/maps/lantiq.c
@@ -0,0 +1,190 @@
+/*
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as published
+ *  by the Free Software Foundation.
+ *
+ *  Copyright (C) 2004 Liu Peng Infineon IFAP DC COM CPE
+ *  Copyright (C) 2010 John Crispin <blogic@openwrt.org>
+ */
+
+#include<linux/module.h>
+#include<linux/types.h>
+#include<linux/kernel.h>
+#include<linux/io.h>
+#include<linux/init.h>
+#include<linux/mtd/mtd.h>
+#include<linux/mtd/map.h>
+#include<linux/mtd/partitions.h>
+#include<linux/mtd/cfi.h>
+#include<linux/platform_device.h>
+#include<linux/mtd/physmap.h>
+
+#include<lantiq_soc.h>
+#include<lantiq_platform.h>
+
+/* the NOR flash is connected to the same external bus unit (EBU) as PCI

   Period at end of statment missing?

+ * to make PCI work we need to enable the endianess swapping of the addr
+ * written to the EBU. this however has some limitations and breaks when
+ * using NOR. it does not really matter if the onflash data is in a swapped
+ * order, however cfi sequences also fail. to workaround this we need to use
+ * a complex map. We essentially software swap all addresses during probe
+ * and then swizzle the unlock addresses.
+ */
+static int ltq_mtd_probing;
+
+static map_word
+ltq_read16(struct map_info *map, unsigned long adr)
+{
+       unsigned long flags;
+
+       map_word temp;

   Empty line should be here, not above.

+       if (ltq_mtd_probing)
+               adr ^= 2;
+       spin_lock_irqsave(&ebu_lock, flags);
+       temp.x[0] = *((__u16 *)(map->virt + adr));
+       spin_unlock_irqrestore(&ebu_lock, flags);

   Hm, what does this lock gain, if the read is atomic anyway?

+void
+ltq_copy_from(struct map_info *map, void *to,
> +  unsigned long from, ssize_t len)

   Shouldn't it be static?

+{
+       unsigned char *p;
+       unsigned char *to_8;
+       unsigned long flags;
+
+       spin_lock_irqsave(&ebu_lock, flags);
+       from = (unsigned long) (map->virt + from);

   Why not:

        from += (unsigned long) map->virt;

like you do in ltq_copy_to()?

+       p = (unsigned char *) from;

   Could be done in initializer, like in ltq_copy_to().

+       to_8 = (unsigned char *) to;
+       while (len--)
+               *to_8++ = *p++;

   BTW, you could use memcpy_fromio().

+       spin_unlock_irqrestore(&ebu_lock, flags);
+}
+
+void
+ltq_copy_to(struct map_info *map, unsigned long to,
+       const void *from, ssize_t len)

   Shouldn't it be static?

+{
+       unsigned char *p =  (unsigned char *)from;
+       unsigned char *to_8;
+       unsigned long flags;
+
+       spin_lock_irqsave(&ebu_lock, flags);
+       to += (unsigned long) map->virt;
+       to_8 = (unsigned char *)to;
+       while (len--)
+               *p++ = *to_8++;

   I think you have this backwards. It should be:

                *to_8++ = *p++;

   BTW, you could use memcpy_toio().

+       spin_unlock_irqrestore(&ebu_lock, flags);
+}
[...]
+static int
+ltq_mtd_probe(struct platform_device *pdev)
+{
+       struct physmap_flash_data *ltq_mtd_data =
+               (struct physmap_flash_data *) dev_get_platdata(&pdev->dev);

   Cast from 'void *' is automatic -- no need for explicit one.

+#ifdef CONFIG_SOC_TYPE_XWAY
+       ltq_ebu_w32(ltq_ebu_r32(LTQ_EBU_BUSCON0) & ~EBU_WRDIS, LTQ_EBU_BUSCON0);
+#endif

   Hm, can't you do this in the platform code?

+       ltq_map.phys = res->start;
+       ltq_map.size = resource_size(res);
+       ltq_map.virt = devm_ioremap_nocache(&pdev->dev, ltq_map.phys,
+               ltq_map.size);

   Hm, could you indent the last line more to the right?

+       if (!ltq_map.virt) {
+               dev_err(&pdev->dev, "failed to ioremap!\n");
+               return -EIO;
+       }
+
+       ltq_mtd_probing = 1;
+       ltq_mtd = (struct mtd_info *) do_map_probe("cfi_probe",&ltq_map);

   do_map_probe() already returns that type, why cast to it?

+       ltq_mtd_probing = 0;
+       if (!ltq_mtd) {
+               iounmap(ltq_map.virt);
+               dev_err(&pdev->dev, "probing failed\n");
+               return -ENXIO;
+       }
+       ltq_mtd->owner = THIS_MODULE;
+
+       cfi = (struct cfi_private *)ltq_map.fldrv_priv;

   Cast from 'void *' is automatic -- no need for explicit one.

+int __init
+init_ltq_mtd(void)
+{
+       int ret = platform_driver_register(&ltq_mtd_driver);

Use platform_driver_probe() instead, as the device is not a hotplug one. Then ltq_mtd_probe() can become '__init'.

WBR, Sergei

<Prev in Thread] Current Thread [Next in Thread>