linux-kernel - Re: [PATCH v2] HID: i2c-hid: Use block reads when possible to save power

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Message-ID: <20200701150007.GA2141@sultan-book.localdomain>
Date:   Wed, 1 Jul 2020 08:00:07 -0700
From:   Sultan Alsawaf <sultan@...neltoast.com>
To:     Jarkko Nikula <jarkko.nikula@...ux.intel.com>
Cc:     aaron.ma@...onical.com, admin@...ma.net,
        andriy.shevchenko@...ux.intel.com, benjamin.tissoires@...hat.com,
        hdegoede@...hat.com, hn.chen@...dahitech.com, jikos@...nel.org,
        kai.heng.feng@...onical.com, linux-i2c@...r.kernel.org,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        mika.westerberg@...ux.intel.com, vicamo.yang@...onical.com,
        wsa@...nel.org
Subject: Re: [PATCH v2] HID: i2c-hid: Use block reads when possible to save
 power

On Wed, Jul 01, 2020 at 11:04:01AM +0300, Jarkko Nikula wrote:
> On 6/29/20 8:43 PM, Sultan Alsawaf wrote:
> > Hmm, for some reason in 5.8 I get the same problem, but 5.7 is fine. Could you
> > try this on 5.7 and see if it works?
> > 
> > In the meantime I'll bisect 5.8 to see why it's causing problems for me...
> > 
> I see the same issue on top of v5.7:

Try reverting my "i2c: designware: Only check the first byte for SMBus block
read length" patch and apply the following change instead:

--- a/drivers/i2c/busses/i2c-designware-master.c
+++ b/drivers/i2c/busses/i2c-designware-master.c
@@ -394,10 +394,12 @@ i2c_dw_read(struct dw_i2c_dev *dev)
 			u32 flags = msgs[dev->msg_read_idx].flags;
 
 			*buf = dw_readl(dev, DW_IC_DATA_CMD);
-			/* Ensure length byte is a valid value */
-			if (flags & I2C_M_RECV_LEN &&
-				*buf <= I2C_SMBUS_BLOCK_MAX && *buf > 0) {
-				len = i2c_dw_recv_len(dev, *buf);
+			if (flags & I2C_M_RECV_LEN) {
+				/* Ensure length byte is a valid value */
+				if (*buf <= I2C_SMBUS_BLOCK_MAX && *buf > 0)
+					len = i2c_dw_recv_len(dev, *buf);
+				else
+					len = i2c_dw_recv_len(dev, len);
 			}
 			buf++;
 			dev->rx_outstanding--;