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Message-ID: <20180226205204.p37lf7dcl5k7az37@ninjato>
Date: Mon, 26 Feb 2018 21:52:04 +0100
From: Wolfram Sang <wsa@...-dreams.de>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Jean Delvare <jdelvare@...e.com>, linux-i2c@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] i2c: piix4: Use request_muxed_region
On Mon, Feb 26, 2018 at 12:46:53PM -0800, Guenter Roeck wrote:
> Accesses to SB800_PIIX4_SMB_IDX can occur from multiple drivers.
> One example for another driver is the sp5100_tco driver.
>
> Use request_muxed_region() to ensure synchronization.
>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
To understand better: How does this relate to the series Zoltan
Boszormenyi was proposing (in one sentence)?
> ---
> v2: Dropped now unnecessary include of linux/mutex.h
> Added error message if request_muxed_region() fails
> Spell out affected driver in commit message
>
> Note that I did not try to do a performance analysis.
> Doing so seemed excessive, even more so in the context of
> piix4_imc_sleep() already using request_muxed_region().
>
> drivers/i2c/busses/i2c-piix4.c | 55 +++++++++++++++++++-----------------------
> 1 file changed, 25 insertions(+), 30 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
> index 4c1f6aaec0fc..90946a8b9a75 100644
> --- a/drivers/i2c/busses/i2c-piix4.c
> +++ b/drivers/i2c/busses/i2c-piix4.c
> @@ -40,7 +40,6 @@
> #include <linux/dmi.h>
> #include <linux/acpi.h>
> #include <linux/io.h>
> -#include <linux/mutex.h>
>
>
> /* PIIX4 SMBus address offsets */
> @@ -153,10 +152,7 @@ static const struct dmi_system_id piix4_dmi_ibm[] = {
>
> /*
> * SB800 globals
> - * piix4_mutex_sb800 protects piix4_port_sel_sb800 and the pair
> - * of I/O ports at SB800_PIIX4_SMB_IDX.
> */
> -static DEFINE_MUTEX(piix4_mutex_sb800);
> static u8 piix4_port_sel_sb800;
> static u8 piix4_port_mask_sb800;
> static u8 piix4_port_shift_sb800;
> @@ -298,12 +294,19 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
> else
> smb_en = (aux) ? 0x28 : 0x2c;
>
> - mutex_lock(&piix4_mutex_sb800);
> + if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2, "sb800_piix4_smb")) {
> + dev_err(&PIIX4_dev->dev,
> + "SMB base address index region 0x%x already in use.\n",
> + SB800_PIIX4_SMB_IDX);
> + return -EBUSY;
> + }
> +
> outb_p(smb_en, SB800_PIIX4_SMB_IDX);
> smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
> outb_p(smb_en + 1, SB800_PIIX4_SMB_IDX);
> smba_en_hi = inb_p(SB800_PIIX4_SMB_IDX + 1);
> - mutex_unlock(&piix4_mutex_sb800);
> +
> + release_region(SB800_PIIX4_SMB_IDX, 2);
>
> if (!smb_en) {
> smb_en_status = smba_en_lo & 0x10;
> @@ -373,7 +376,12 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
> break;
> }
> } else {
> - mutex_lock(&piix4_mutex_sb800);
> + if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2,
> + "sb800_piix4_smb")) {
> + release_region(piix4_smba, SMBIOSIZE);
> + return -EBUSY;
> + }
> +
> outb_p(SB800_PIIX4_PORT_IDX_SEL, SB800_PIIX4_SMB_IDX);
> port_sel = inb_p(SB800_PIIX4_SMB_IDX + 1);
> piix4_port_sel_sb800 = (port_sel & 0x01) ?
> @@ -381,7 +389,7 @@ static int piix4_setup_sb800(struct pci_dev *PIIX4_dev,
> SB800_PIIX4_PORT_IDX;
> piix4_port_mask_sb800 = SB800_PIIX4_PORT_IDX_MASK;
> piix4_port_shift_sb800 = SB800_PIIX4_PORT_IDX_SHIFT;
> - mutex_unlock(&piix4_mutex_sb800);
> + release_region(SB800_PIIX4_SMB_IDX, 2);
> }
>
> dev_info(&PIIX4_dev->dev,
> @@ -679,7 +687,8 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
> u8 port;
> int retval;
>
> - mutex_lock(&piix4_mutex_sb800);
> + if (!request_muxed_region(SB800_PIIX4_SMB_IDX, 2, "sb800_piix4_smb"))
> + return -EBUSY;
>
> /* Request the SMBUS semaphore, avoid conflicts with the IMC */
> smbslvcnt = inb_p(SMBSLVCNT);
> @@ -695,8 +704,8 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
> } while (--retries);
> /* SMBus is still owned by the IMC, we give up */
> if (!retries) {
> - mutex_unlock(&piix4_mutex_sb800);
> - return -EBUSY;
> + retval = -EBUSY;
> + goto release;
> }
>
> /*
> @@ -753,8 +762,8 @@ static s32 piix4_access_sb800(struct i2c_adapter *adap, u16 addr,
> if ((size == I2C_SMBUS_BLOCK_DATA) && adapdata->notify_imc)
> piix4_imc_wakeup();
>
> - mutex_unlock(&piix4_mutex_sb800);
> -
> +release:
> + release_region(SB800_PIIX4_SMB_IDX, 2);
> return retval;
> }
>
> @@ -899,13 +908,6 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
> bool notify_imc = false;
> is_sb800 = true;
>
> - if (!request_region(SB800_PIIX4_SMB_IDX, 2, "smba_idx")) {
> - dev_err(&dev->dev,
> - "SMBus base address index region 0x%x already in use!\n",
> - SB800_PIIX4_SMB_IDX);
> - return -EBUSY;
> - }
> -
> if (dev->vendor == PCI_VENDOR_ID_AMD &&
> dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS) {
> u8 imc;
> @@ -922,20 +924,16 @@ static int piix4_probe(struct pci_dev *dev, const struct pci_device_id *id)
>
> /* base address location etc changed in SB800 */
> retval = piix4_setup_sb800(dev, id, 0);
> - if (retval < 0) {
> - release_region(SB800_PIIX4_SMB_IDX, 2);
> + if (retval < 0)
> return retval;
> - }
>
> /*
> * Try to register multiplexed main SMBus adapter,
> * give up if we can't
> */
> retval = piix4_add_adapters_sb800(dev, retval, notify_imc);
> - if (retval < 0) {
> - release_region(SB800_PIIX4_SMB_IDX, 2);
> + if (retval < 0)
> return retval;
> - }
> } else {
> retval = piix4_setup(dev, id);
> if (retval < 0)
> @@ -983,11 +981,8 @@ static void piix4_adap_remove(struct i2c_adapter *adap)
>
> if (adapdata->smba) {
> i2c_del_adapter(adap);
> - if (adapdata->port == (0 << piix4_port_shift_sb800)) {
> + if (adapdata->port == (0 << piix4_port_shift_sb800))
> release_region(adapdata->smba, SMBIOSIZE);
> - if (adapdata->sb800_main)
> - release_region(SB800_PIIX4_SMB_IDX, 2);
> - }
> kfree(adapdata);
> kfree(adap);
> }
> --
> 2.7.4
>
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